On 24/09/2022 13:44, amdx wrote:
> On 9/24/2022 6:47 AM, piglet wrote:
>> On 24/09/2022 11:58, amdx wrote:
>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>> especially at the higher frequencies where it drops pretty low.
>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>   Can you give a little detail on how you would implement it? And
>>>>> what happens to gain and frequency response?
>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>> but when was it first used in an electrical circuit?
>>>>> I did manage to find a bootstrapped tube circuit, but it didn't use
>>>>> a 100MΩ grid resistor, Is that a detriment to adding bootstrapping?
>>>>>   I made my proposed idea on the right side.
>>>>> Hmm, the problem is more the tube input than the 100MΩ, does
>>>>> bootstrapping help that?
>>>>>   Might be barking up the wrong tree.
>>>>>
>>>>>  >
>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>
>>>>>
>>>>>
>>>>>                              Thanks, Mikek
>>>>>
>>>>
>>>> Did you see the value of C302? I think V301 is being used in the so
>>>> called "infinite impedance" detector configuration. The cathode
>>>> voltage is not the buffered grid ac input but instead is a dc level
>>>> representing something between the peak and average ac input. So AC
>>>> bootstrapping that circuit not possible. I guess you could insert a
>>>> whole new hi-z buffer between tuned circuit under test and detector
>>>> but in practice it would be difficult to get it to be an improvement?
>>>>
>>>> piglet
>>>>
>>>
>>>   I thought I'd seen it referred to as an "infinite impedance
>>> detector", but don't find it in the manual.
>>> I do see this line in the manual and don't understand how transit
>>> time loss in the voltmeter
>>> tube causes a shunt resistance across the measuring circuit at High
>>> Frequencies.
>>> Can someone provide a simple explanation?
>>>
>>> "QVOLTMETERCONDUCTANCE.
>>> Anotherinternalparameterwhich causestheindi-
>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>> andveryhighfrequencies, is theinputconductanceof
>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>> conductance consistsofa 100megohmgridleak resistor
>>> inparallelwiththeinternallossesofthevacuum tube.
>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>> metertubeshuntstheresonatingcapacitorandintro-
>>> duces ashuntresistance acrossthemeasuring circuit"
>>>
>>> Someone has developed a single fet circuit that does an OK job.
>>> I always wanted to try this circuit,
>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>
>>>   But have not got to it yet, to much computer time and not enough
>>> bench time.
>>>                                        Mikek
>>>
>>>
>>>
>>
>> The transit time part comes into it like this: due to the electron
>> travel time there is a short delay before grid voltage changes during
>> the positive peaks get to influence the cathode voltage. At very high
>> frequencies this increased loading at the peaks gets more significant.
>>
>> The 535A tube is quite large and looks like it was built for low
>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>> like an acorn device may have had shorter delay times.
>>
>> Looks to me like that bootstrap all nodes fet buffer came straight out
>> of a late 1960s-early 70s NatSemi app note.
>>
>> piglet
>>
>   Yes, it did, but, the question is will it work in place of the tube?
>                                              Thanks, Mikek

The touted capacitance of the bootstrapped fet is 0.25pF which at 50MHz
is reactance of 13kohm. If it were a good capacitance you could resonate
it away but it probably is very lossy and a lousy "capacitor" so that
fet buffer could be worse than just leaving the Boonton alone. Since
your main interest is around 1.5MHz you perhaps needn't worry a lot
about behavior at 50MHz?

piglet

On Tue, 27 Sep 2022 06:49:46 +0100, piglet <erichpwagner@hotmail.com>
wrote:

>On 26/09/2022 19:47, Ricky wrote:
>> On Monday, September 26, 2022 at 7:24:26 AM UTC-4, amdx wrote:
>>> On 9/25/2022 10:49 PM, John Larkin wrote:
>>>> On Sun, 25 Sep 2022 21:37:54 -0500, amdx <am...@knology.net> wrote:
>>>>
>>>>> On 9/25/2022 3:22 PM, John Larkin wrote:
>>>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <am...@knology.net> wrote:
>>>>>>
>>>>>>> On one of the groups I monitor, it was ask if the tube circuit shown
>>>>>>> below could be bootstrapped to raise the input impedance,
>>>>>>> especially at the higher frequencies where it drops pretty low. (purpose
>>>>>>> is to reduce loading on the LC being measured--Q meter)
>>>>>>> Can you give a little detail on how you would implement it? And what
>>>>>>> happens to gain and frequency response?
>>>>>>> When was bootstrapping introduced, the word started in the 1880s, but
>>>>>>> when was it first used in an electrical circuit?
>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't use a
>>>>>>> 100M? grid resistor, Is that a detriment to adding bootstrapping?
>>>>>>> I made my proposed idea on the right side.
>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>> bootstrapping help that?
>>>>>>> Might be barking up the wrong tree.
>>>>>>>
>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>
>>>>>>>
>>>>>>> Thanks, Mikek
>>>>>> Here's a High-Q resonator we created at lunch today:
>>>>>>
>>>>>> https://www.dropbox.com/s/eeocp4rvgaz2dis/Hi-Q_resonator.MOV?dl=0
>>>>>>
>>>>>> entirely by accident. There may be a gain mechanism involved.
>>>>>>
>>>>> Air currents from the fan sloshing around in the bowl adding gain?
>>>>>
>>>>> I had comments on another group about bootstrapping the tube.
>>>>>
>>>>> "The V301 valve in the Boonton Q meter is NOT a cathode follower
>>>>> but an " infinite impedance detector" due to the capacitor C302.
>>>>> So you cannot bootstrap at AC."
>>>>>
>>>>> That's beyond my level.
>>>> The triode is acting like a rectifier into C201 so it can drive a DC
>>>> meter.
>>>>
>>>> But a little grid capacitance can be, probably already is, calibrated
>>>> out of the circuit.
>>>>
>>>> A triode grid has a resistive component that reduces Q a bit. I don't
>>>> know the magnitude of that.
>>>>
>>> Here's the graph of how the input resistance drops from almost 100M?
>>> at 50kHz to 57k? at 50MHz.
>>>> https://www.dropbox.com/s/5wc0htizojcp4xu/Boonton%20Input%20impedance%20vs%20Frequency.jpg?dl=0
>>>
>>> Mikek
>>
>> Don't you think C201A and C201B have something to do with that?
>>
>> How are they adjusted? Is this like the trim capacitance in a scope probe? But it is in the wrong place.
>>
>
>C201 is part of the resonant tuned circuit, they will be big solid parts
>(probably silver plated) with very low loss and high Q. The drop of
>input impedance is due to the tube transit delay as discussed up thread.

Most of the cycle, especially at high Q, the tube is in cutoff, so
there is no transit delay.

The tube likely has a minor effect on Q measurement.

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

> All the usual definitions of Q and resonant frequency give the same
> results at high Q, but not at low Q. You have to pay attention for Q <~
> 10.
>
> Cheers
>
> Phil Hobbs

Q < 4

Radiotron Designer's Handbook
Chapter 9 Tuned Circuits
SECTION 2: DAMPED OSCILLATIONS

https://tinyurl.com/mvkhesey

--
MRM

On 9/26/2022 1:47 PM, Ricky wrote:
> On Monday, September 26, 2022 at 7:24:26 AM UTC-4, amdx wrote:
>> On 9/25/2022 10:49 PM, John Larkin wrote:
>>> On Sun, 25 Sep 2022 21:37:54 -0500, amdx <am...@knology.net> wrote:
>>>
>>>> On 9/25/2022 3:22 PM, John Larkin wrote:
>>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <am...@knology.net> wrote:
>>>>>
>>>>>> On one of the groups I monitor, it was ask if the tube circuit shown
>>>>>> below could be bootstrapped to raise the input impedance,
>>>>>> especially at the higher frequencies where it drops pretty low. (purpose
>>>>>> is to reduce loading on the LC being measured--Q meter)
>>>>>> Can you give a little detail on how you would implement it? And what
>>>>>> happens to gain and frequency response?
>>>>>> When was bootstrapping introduced, the word started in the 1880s, but
>>>>>> when was it first used in an electrical circuit?
>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't use a
>>>>>> 100M? grid resistor, Is that a detriment to adding bootstrapping?
>>>>>> I made my proposed idea on the right side.
>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>> bootstrapping help that?
>>>>>> Might be barking up the wrong tree.
>>>>>>
>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>
>>>>>>
>>>>>> Thanks, Mikek
>>>>> Here's a High-Q resonator we created at lunch today:
>>>>>
>>>>> https://www.dropbox.com/s/eeocp4rvgaz2dis/Hi-Q_resonator.MOV?dl=0
>>>>>
>>>>> entirely by accident. There may be a gain mechanism involved.
>>>>>
>>>> Air currents from the fan sloshing around in the bowl adding gain?
>>>>
>>>> I had comments on another group about bootstrapping the tube.
>>>>
>>>> "The V301 valve in the Boonton Q meter is NOT a cathode follower
>>>> but an " infinite impedance detector" due to the capacitor C302.
>>>> So you cannot bootstrap at AC."
>>>>
>>>> That's beyond my level.
>>> The triode is acting like a rectifier into C201 so it can drive a DC
>>> meter.
>>>
>>> But a little grid capacitance can be, probably already is, calibrated
>>> out of the circuit.
>>>
>>> A triode grid has a resistive component that reduces Q a bit. I don't
>>> know the magnitude of that.
>>>
>> Here's the graph of how the input resistance drops from almost 100MΩ
>> at 50kHz to 57kΩ at 50MHz.
>>> https://www.dropbox.com/s/5wc0htizojcp4xu/Boonton%20Input%20impedance%20vs%20Frequency.jpg?dl=0
>> Mikek
> Don't you think C201A and C201B have something to do with that?
>
> How are they adjusted? Is this like the trim capacitance in a scope probe? But it is in the wrong place.
>
Those are the tuning caps to get resonance. The small one is a vernier
+/- 3pf.
 Yes, I'm sure they add to the loss resistance, I read once the tuning
capacitor had a Q of 20,000, but no mention of
at what frequency or capacitance setting, so may have been the maximum.
                                Mikek

On 9/27/2022 3:59 AM, piglet wrote:
> On 24/09/2022 13:44, amdx wrote:
>> On 9/24/2022 6:47 AM, piglet wrote:
>>> On 24/09/2022 11:58, amdx wrote:
>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>> what happens to gain and frequency response?
>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>> but when was it first used in an electrical circuit?
>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>> use a 100MΩ grid resistor, Is that a detriment to adding
>>>>>> bootstrapping?
>>>>>>   I made my proposed idea on the right side.
>>>>>> Hmm, the problem is more the tube input than the 100MΩ, does
>>>>>> bootstrapping help that?
>>>>>>   Might be barking up the wrong tree.
>>>>>>
>>>>>>  >
>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>
>>>>>>
>>>>>>
>>>>>>                              Thanks, Mikek
>>>>>>
>>>>>
>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>> level representing something between the peak and average ac
>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>> test and detector but in practice it would be difficult to get it
>>>>> to be an improvement?
>>>>>
>>>>> piglet
>>>>>
>>>>
>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>> detector", but don't find it in the manual.
>>>> I do see this line in the manual and don't understand how transit
>>>> time loss in the voltmeter
>>>> tube causes a shunt resistance across the measuring circuit at High
>>>> Frequencies.
>>>> Can someone provide a simple explanation?
>>>>
>>>> "QVOLTMETERCONDUCTANCE.
>>>> Anotherinternalparameterwhich causestheindi-
>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>> andveryhighfrequencies, is theinputconductanceof
>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>> conductance consistsofa 100megohmgridleak resistor
>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>
>>>> Someone has developed a single fet circuit that does an OK job.
>>>> I always wanted to try this circuit,
>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>
>>>>   But have not got to it yet, to much computer time and not enough
>>>> bench time.
>>>>                                        Mikek
>>>>
>>>>
>>>>
>>>
>>> The transit time part comes into it like this: due to the electron
>>> travel time there is a short delay before grid voltage changes
>>> during the positive peaks get to influence the cathode voltage. At
>>> very high frequencies this increased loading at the peaks gets more
>>> significant.
>>>
>>> The 535A tube is quite large and looks like it was built for low
>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>> like an acorn device may have had shorter delay times.
>>>
>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>> out of a late 1960s-early 70s NatSemi app note.
>>>
>>> piglet
>>>
>>    Yes, it did, but, the question is will it work in place of the tube?
>>                                               Thanks, Mikek
>
> The touted capacitance of the bootstrapped fet is 0.25pF which at
> 50MHz is reactance of 13kohm.

 I would think any capacitance just adds to the resonating capacitance,
so just need to calculate in the loss of the capacitance, not the
capacitance.

> Since your main interest is around 1.5MHz you perhaps needn't worry a
> lot about behavior at 50MHz?

 That is very true, but as the much maligned John Larkin said, "this is
a discussion group" so, I'm having the topic discussed!

Mikek

On 27/09/2022 17:07, John Larkin wrote:
> On Tue, 27 Sep 2022 06:49:46 +0100, piglet <erichpwagner@hotmail.com>
> wrote:
>
>> On 26/09/2022 19:47, Ricky wrote:
>>> On Monday, September 26, 2022 at 7:24:26 AM UTC-4, amdx wrote:
>>>> On 9/25/2022 10:49 PM, John Larkin wrote:
>>>>> On Sun, 25 Sep 2022 21:37:54 -0500, amdx <am...@knology.net> wrote:
>>>>>
>>>>>> On 9/25/2022 3:22 PM, John Larkin wrote:
>>>>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <am...@knology.net> wrote:
>>>>>>>
>>>>>>>> On one of the groups I monitor, it was ask if the tube circuit shown
>>>>>>>> below could be bootstrapped to raise the input impedance,
>>>>>>>> especially at the higher frequencies where it drops pretty low. (purpose
>>>>>>>> is to reduce loading on the LC being measured--Q meter)
>>>>>>>> Can you give a little detail on how you would implement it? And what
>>>>>>>> happens to gain and frequency response?
>>>>>>>> When was bootstrapping introduced, the word started in the 1880s, but
>>>>>>>> when was it first used in an electrical circuit?
>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't use a
>>>>>>>> 100M? grid resistor, Is that a detriment to adding bootstrapping?
>>>>>>>> I made my proposed idea on the right side.
>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>> bootstrapping help that?
>>>>>>>> Might be barking up the wrong tree.
>>>>>>>>
>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>
>>>>>>>>
>>>>>>>> Thanks, Mikek
>>>>>>> Here's a High-Q resonator we created at lunch today:
>>>>>>>
>>>>>>> https://www.dropbox.com/s/eeocp4rvgaz2dis/Hi-Q_resonator.MOV?dl=0
>>>>>>>
>>>>>>> entirely by accident. There may be a gain mechanism involved.
>>>>>>>
>>>>>> Air currents from the fan sloshing around in the bowl adding gain?
>>>>>>
>>>>>> I had comments on another group about bootstrapping the tube.
>>>>>>
>>>>>> "The V301 valve in the Boonton Q meter is NOT a cathode follower
>>>>>> but an " infinite impedance detector" due to the capacitor C302.
>>>>>> So you cannot bootstrap at AC."
>>>>>>
>>>>>> That's beyond my level.
>>>>> The triode is acting like a rectifier into C201 so it can drive a DC
>>>>> meter.
>>>>>
>>>>> But a little grid capacitance can be, probably already is, calibrated
>>>>> out of the circuit.
>>>>>
>>>>> A triode grid has a resistive component that reduces Q a bit. I don't
>>>>> know the magnitude of that.
>>>>>
>>>> Here's the graph of how the input resistance drops from almost 100M?
>>>> at 50kHz to 57k? at 50MHz.
>>>>> https://www.dropbox.com/s/5wc0htizojcp4xu/Boonton%20Input%20impedance%20vs%20Frequency.jpg?dl=0
>>>>
>>>> Mikek
>>>
>>> Don't you think C201A and C201B have something to do with that?
>>>
>>> How are they adjusted? Is this like the trim capacitance in a scope probe? But it is in the wrong place.
>>>
>>
>> C201 is part of the resonant tuned circuit, they will be big solid parts
>> (probably silver plated) with very low loss and high Q. The drop of
>> input impedance is due to the tube transit delay as discussed up thread.
>
> Most of the cycle, especially at high Q, the tube is in cutoff, so
> there is no transit delay.
>
> The tube likely has a minor effect on Q measurement.
>

100% agree!

piglet

amdx <amdx@knology.net> wrote:
> On 9/27/2022 3:59 AM, piglet wrote:
> > On 24/09/2022 13:44, amdx wrote:
> >> On 9/24/2022 6:47 AM, piglet wrote:
> >>> On 24/09/2022 11:58, amdx wrote:
> >>>> On 9/24/2022 1:11 AM, piglet wrote:
> >>>>> On 24/09/2022 00:33, amdx wrote:
> >>>>>> ??On one of the groups I monitor, it was ask if the tube circuit
> >>>>>> shown below could be bootstrapped to raise the input impedance,
> >>>>>> especially at the higher frequencies where it drops pretty low.
> >>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
> >>>>>> ??Can you give a little detail on how you would implement it? And
> >>>>>> what happens to gain and frequency response?
> >>>>>> When was bootstrapping introduced, the word started in the 1880s,
> >>>>>> but when was it first used in an electrical circuit?
> >>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
> >>>>>> use a 100M? grid resistor, Is that a detriment to adding
> >>>>>> bootstrapping?
> >>>>>> ??I made my proposed idea on the right side.
> >>>>>> Hmm, the problem is more the tube input than the 100M?, does
> >>>>>> bootstrapping help that?
> >>>>>> ??Might be barking up the wrong tree.
> >>>>>>
> >>>>>> ?>
> >>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> ???????????????????????????? Thanks, Mikek
> >>>>>>
> >>>>>
> >>>>> Did you see the value of C302? I think V301 is being used in the
> >>>>> so called "infinite impedance" detector configuration. The cathode
> >>>>> voltage is not the buffered grid ac input but instead is a dc
> >>>>> level representing something between the peak and average ac
> >>>>> input. So AC bootstrapping that circuit not possible. I guess you
> >>>>> could insert a whole new hi-z buffer between tuned circuit under
> >>>>> test and detector but in practice it would be difficult to get it
> >>>>> to be an improvement?
> >>>>>
> >>>>> piglet
> >>>>>
> >>>>
> >>>> ??I thought I'd seen it referred to as an "infinite impedance
> >>>> detector", but don't find it in the manual.
> >>>> I do see this line in the manual and don't understand how transit
> >>>> time loss in the voltmeter
> >>>> tube causes a shunt resistance across the measuring circuit at High
> >>>> Frequencies.
> >>>> Can someone provide a simple explanation?
> >>>>
> >>>> "QVOLTMETERCONDUCTANCE.
> >>>> Anotherinternalparameterwhich causestheindi-
> >>>> catedQtodeviatefromeffectiveQ,atbothvery low
> >>>> andveryhighfrequencies, is theinputconductanceof
> >>>> theQvoltmeter circuit.Atvery low frequenciesthis
> >>>> conductance consistsofa 100megohmgridleak resistor
> >>>> inparallelwiththeinternallossesofthevacuum tube.
> >>>> Atveryhighfrequenciesthetransittime lossinthevolt-
> >>>> metertubeshuntstheresonatingcapacitorandintro-
> >>>> duces ashuntresistance acrossthemeasuring circuit"
> >>>>
> >>>> Someone has developed a single fet circuit that does an OK job.
> >>>> I always wanted to try this circuit,
> >>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
> >>>>>
> >>>> ??But have not got to it yet, to much computer time and not enough
> >>>> bench time.
> >>>> ?????????????????????????????????????? Mikek
> >>>>
> >>>>
> >>>>
> >>>
> >>> The transit time part comes into it like this: due to the electron
> >>> travel time there is a short delay before grid voltage changes
> >>> during the positive peaks get to influence the cathode voltage. At
> >>> very high frequencies this increased loading at the peaks gets more
> >>> significant.
> >>>
> >>> The 535A tube is quite large and looks like it was built for low
> >>> inter-electrode capacity and low leakage. For VHF use a smaller tube
> >>> like an acorn device may have had shorter delay times.
> >>>
> >>> Looks to me like that bootstrap all nodes fet buffer came straight
> >>> out of a late 1960s-early 70s NatSemi app note.
> >>>
> >>> piglet
> >>>
> >> ?? Yes, it did, but, the question is will it work in place of the tube?
> >> ????????????????????????????????????????????? Thanks, Mikek
> >
> > The touted capacitance of the bootstrapped fet is 0.25pF which at
> > 50MHz is reactance of 13kohm.
>
> ?I would think any capacitance just adds to the resonating capacitance,
> so just need to calculate in the loss of the capacitance, not the
> capacitance.
>
> > Since your main interest is around 1.5MHz you perhaps needn't worry a
> > lot about behavior at 50MHz?
>
> ?That is very true, but as the much maligned John Larkin said, "this is
> a discussion group" so, I'm having the topic discussed!

The sub-circuit you discuss is just a RF voltmeter. You want low
losses, that is high resistance. Having high resistance on RF side
is tricky and Boonton result looks good. It is not clear if
complicated RF circuit could better. OTOH, since voltages are
high I would try Silicon diode (say 1N4148 at first), with very
small load on rectified side something like 1M or 10M. To measure
this voltage you need a buffer amplifier, something like TL084 have
enough range and presents very small load. So with 10M resitor
load would be 10M + diode leakage + losses due to charge in
junction. 1N4148 has reverse recovery time of 4ns, this may be
better than tube. If 1N4148 works resonably well one could
search for better diodes.
--
Waldek Hebisch

On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:

>On 9/27/2022 3:59 AM, piglet wrote:
>> On 24/09/2022 13:44, amdx wrote:
>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>> On 24/09/2022 11:58, amdx wrote:
>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>> what happens to gain and frequency response?
>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>> but when was it first used in an electrical circuit?
>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>> bootstrapping?
>>>>>>>   I made my proposed idea on the right side.
>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>> bootstrapping help that?
>>>>>>>   Might be barking up the wrong tree.
>>>>>>>
>>>>>>>  >
>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>                              Thanks, Mikek
>>>>>>>
>>>>>>
>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>> level representing something between the peak and average ac
>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>> test and detector but in practice it would be difficult to get it
>>>>>> to be an improvement?
>>>>>>
>>>>>> piglet
>>>>>>
>>>>>
>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>> detector", but don't find it in the manual.
>>>>> I do see this line in the manual and don't understand how transit
>>>>> time loss in the voltmeter
>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>> Frequencies.
>>>>> Can someone provide a simple explanation?
>>>>>
>>>>> "QVOLTMETERCONDUCTANCE.
>>>>> Anotherinternalparameterwhich causestheindi-
>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>
>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>> I always wanted to try this circuit,
>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>
>>>>>   But have not got to it yet, to much computer time and not enough
>>>>> bench time.
>>>>>                                        Mikek
>>>>>
>>>>>
>>>>>
>>>>
>>>> The transit time part comes into it like this: due to the electron
>>>> travel time there is a short delay before grid voltage changes
>>>> during the positive peaks get to influence the cathode voltage. At
>>>> very high frequencies this increased loading at the peaks gets more
>>>> significant.
>>>>
>>>> The 535A tube is quite large and looks like it was built for low
>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>> like an acorn device may have had shorter delay times.
>>>>
>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>
>>>> piglet
>>>>
>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>                                               Thanks, Mikek
>>
>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>> 50MHz is reactance of 13kohm.
>
>  I would think any capacitance just adds to the resonating capacitance,
>so just need to calculate in the loss of the capacitance, not the
>capacitance.
>
>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>> lot about behavior at 50MHz?
>
>  That is very true, but as the much maligned John Larkin said, "this is
>a discussion group" so, I'm having the topic discussed!
>
>Mikek

I'm not maligned by anybody that matters. That's by definition.

On 9/29/2022 5:42 PM, John Larkin wrote:
> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/27/2022 3:59 AM, piglet wrote:
>>> On 24/09/2022 13:44, amdx wrote:
>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>>> what happens to gain and frequency response?
>>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>> bootstrapping?
>>>>>>>>   I made my proposed idea on the right side.
>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>> bootstrapping help that?
>>>>>>>>   Might be barking up the wrong tree.
>>>>>>>>
>>>>>>>>  >
>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>                              Thanks, Mikek
>>>>>>>>
>>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>> level representing something between the peak and average ac
>>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>>> test and detector but in practice it would be difficult to get it
>>>>>>> to be an improvement?
>>>>>>>
>>>>>>> piglet
>>>>>>>
>>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>>> detector", but don't find it in the manual.
>>>>>> I do see this line in the manual and don't understand how transit
>>>>>> time loss in the voltmeter
>>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>>> Frequencies.
>>>>>> Can someone provide a simple explanation?
>>>>>>
>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>
>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>> I always wanted to try this circuit,
>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>
>>>>>>   But have not got to it yet, to much computer time and not enough
>>>>>> bench time.
>>>>>>                                        Mikek
>>>>>>
>>>>>>
>>>>>>
>>>>> The transit time part comes into it like this: due to the electron
>>>>> travel time there is a short delay before grid voltage changes
>>>>> during the positive peaks get to influence the cathode voltage. At
>>>>> very high frequencies this increased loading at the peaks gets more
>>>>> significant.
>>>>>
>>>>> The 535A tube is quite large and looks like it was built for low
>>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>>> like an acorn device may have had shorter delay times.
>>>>>
>>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>
>>>>> piglet
>>>>>
>>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>>                                               Thanks, Mikek
>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>> 50MHz is reactance of 13kohm.
>>  I would think any capacitance just adds to the resonating capacitance,
>> so just need to calculate in the loss of the capacitance, not the
>> capacitance.
>>
>>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>>> lot about behavior at 50MHz?
>>  That is very true, but as the much maligned John Larkin said, "this is
>> a discussion group" so, I'm having the topic discussed!
>>
>> Mikek
> I'm not maligned by anybody that matters. That's by definition.
>
 Agreed and, I looked it up before I used it, I thought it fit well.

"If you describe someone or something as much-maligned,
you mean that *they are often criticized by people,
but you think the criticism is unfair or exaggerated because they have
good qualities too*."

  The people that criticize you have a political opinion and they have
to go after you personally
rather than argue their point. That don't like it when you have a good
point, so they malign you.
                                             Mikek

On Thu, 29 Sep 2022 23:23:18 -0500, amdx <amdx@knology.net> wrote:

>On 9/29/2022 5:42 PM, John Larkin wrote:
>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>> On 24/09/2022 13:44, amdx wrote:
>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>>>> what happens to gain and frequency response?
>>>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>>> bootstrapping?
>>>>>>>>>   I made my proposed idea on the right side.
>>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>>> bootstrapping help that?
>>>>>>>>>   Might be barking up the wrong tree.
>>>>>>>>>
>>>>>>>>>  >
>>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>                              Thanks, Mikek
>>>>>>>>>
>>>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>>> level representing something between the peak and average ac
>>>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>>>> test and detector but in practice it would be difficult to get it
>>>>>>>> to be an improvement?
>>>>>>>>
>>>>>>>> piglet
>>>>>>>>
>>>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>>>> detector", but don't find it in the manual.
>>>>>>> I do see this line in the manual and don't understand how transit
>>>>>>> time loss in the voltmeter
>>>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>>>> Frequencies.
>>>>>>> Can someone provide a simple explanation?
>>>>>>>
>>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>>
>>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>>> I always wanted to try this circuit,
>>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>>
>>>>>>>   But have not got to it yet, to much computer time and not enough
>>>>>>> bench time.
>>>>>>>                                        Mikek
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> The transit time part comes into it like this: due to the electron
>>>>>> travel time there is a short delay before grid voltage changes
>>>>>> during the positive peaks get to influence the cathode voltage. At
>>>>>> very high frequencies this increased loading at the peaks gets more
>>>>>> significant.
>>>>>>
>>>>>> The 535A tube is quite large and looks like it was built for low
>>>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>>>> like an acorn device may have had shorter delay times.
>>>>>>
>>>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>>
>>>>>> piglet
>>>>>>
>>>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>>>                                               Thanks, Mikek
>>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>>> 50MHz is reactance of 13kohm.
>>>  I would think any capacitance just adds to the resonating capacitance,
>>> so just need to calculate in the loss of the capacitance, not the
>>> capacitance.
>>>
>>>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>>>> lot about behavior at 50MHz?
>>>  That is very true, but as the much maligned John Larkin said, "this is
>>> a discussion group" so, I'm having the topic discussed!
>>>
>>> Mikek
>> I'm not maligned by anybody that matters. That's by definition.
>>
>  Agreed and, I looked it up before I used it, I thought it fit well.
>
>"If you describe someone or something as much-maligned,
>you mean that *they are often criticized by people,
>but you think the criticism is unfair or exaggerated because they have
>good qualities too*."
>
>   The people that criticize you have a political opinion and they have
>to go after you personally
>rather than argue their point. That don't like it when you have a good
>point, so they malign you.
>                                              Mikek

Because they can't design electronics.

On 9/30/2022 12:01 AM, John Larkin wrote:
> On Thu, 29 Sep 2022 23:23:18 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/29/2022 5:42 PM, John Larkin wrote:
>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>>>
>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>>>>> what happens to gain and frequency response?
>>>>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>>>> bootstrapping?
>>>>>>>>>>   I made my proposed idea on the right side.
>>>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>>>> bootstrapping help that?
>>>>>>>>>>   Might be barking up the wrong tree.
>>>>>>>>>>
>>>>>>>>>>  >
>>>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>                              Thanks, Mikek
>>>>>>>>>>
>>>>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>>>> level representing something between the peak and average ac
>>>>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>>>>> test and detector but in practice it would be difficult to get it
>>>>>>>>> to be an improvement?
>>>>>>>>>
>>>>>>>>> piglet
>>>>>>>>>
>>>>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>>>>> detector", but don't find it in the manual.
>>>>>>>> I do see this line in the manual and don't understand how transit
>>>>>>>> time loss in the voltmeter
>>>>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>>>>> Frequencies.
>>>>>>>> Can someone provide a simple explanation?
>>>>>>>>
>>>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>>>
>>>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>>>> I always wanted to try this circuit,
>>>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>>>
>>>>>>>>   But have not got to it yet, to much computer time and not enough
>>>>>>>> bench time.
>>>>>>>>                                        Mikek
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> The transit time part comes into it like this: due to the electron
>>>>>>> travel time there is a short delay before grid voltage changes
>>>>>>> during the positive peaks get to influence the cathode voltage. At
>>>>>>> very high frequencies this increased loading at the peaks gets more
>>>>>>> significant.
>>>>>>>
>>>>>>> The 535A tube is quite large and looks like it was built for low
>>>>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>>>>> like an acorn device may have had shorter delay times.
>>>>>>>
>>>>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>>>
>>>>>>> piglet
>>>>>>>
>>>>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>>>>                                               Thanks, Mikek
>>>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>>>> 50MHz is reactance of 13kohm.
>>>>  I would think any capacitance just adds to the resonating capacitance,
>>>> so just need to calculate in the loss of the capacitance, not the
>>>> capacitance.
>>>>
>>>>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>>>>> lot about behavior at 50MHz?
>>>>  That is very true, but as the much maligned John Larkin said, "this is
>>>> a discussion group" so, I'm having the topic discussed!
>>>>
>>>> Mikek
>>> I'm not maligned by anybody that matters. That's by definition.
>>>
>>  Agreed and, I looked it up before I used it, I thought it fit well.
>>
>> "If you describe someone or something as much-maligned,
>> you mean that *they are often criticized by people,
>> but you think the criticism is unfair or exaggerated because they have
>> good qualities too*."
>>
>>   The people that criticize you have a political opinion and they have
>> to go after you personally
>> rather than argue their point. That don't like it when you have a good
>> point, so they malign you.
>>                                              Mikek
> Because they can't design electronics.
>
Neither can I, but I'm not maligning you!

 btw, I got the 1000 Hz bandpass to work, it was tuned to 1008 Hz.
I wanted it to use to set the focal point of a parabolic mic.
 I could not get a clean voltage measurement because of all the other
environmental sound. I added the 1008 Hz bandpass filter between my
preamp and amp, then, with an app on my phone that I put across the room,
I generated a 1008Hz sine wave, and had a very clean,
stable waveform on my scope. Easy peasy, I moved the mic about 3"
further away from where I thought the focus was, and doubled the Voltage
output.
 4 hrs building the bandpass filter for a 3 minute adjustment!
 Also, I have never seen this on a parabolic mic, I put a small funnel
on the mic
this also increased my output voltage.

  I used a sensitive, low noise AOM-PU5024 mic,
> https://api.puiaudio.com/file/8a1a7f37-cd74-49b0-81f3-f74090655669.pdf

On Fri, 30 Sep 2022 08:29:07 -0500, amdx <amdx@knology.net> wrote:

>On 9/30/2022 12:01 AM, John Larkin wrote:
>> On Thu, 29 Sep 2022 23:23:18 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/29/2022 5:42 PM, John Larkin wrote:
>>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>>>>
>>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>>>>>> what happens to gain and frequency response?
>>>>>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>>>>> bootstrapping?
>>>>>>>>>>>   I made my proposed idea on the right side.
>>>>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>>>>> bootstrapping help that?
>>>>>>>>>>>   Might be barking up the wrong tree.
>>>>>>>>>>>
>>>>>>>>>>>  >
>>>>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>                              Thanks, Mikek
>>>>>>>>>>>
>>>>>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>>>>> level representing something between the peak and average ac
>>>>>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>>>>>> test and detector but in practice it would be difficult to get it
>>>>>>>>>> to be an improvement?
>>>>>>>>>>
>>>>>>>>>> piglet
>>>>>>>>>>
>>>>>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>>>>>> detector", but don't find it in the manual.
>>>>>>>>> I do see this line in the manual and don't understand how transit
>>>>>>>>> time loss in the voltmeter
>>>>>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>>>>>> Frequencies.
>>>>>>>>> Can someone provide a simple explanation?
>>>>>>>>>
>>>>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>>>>
>>>>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>>>>> I always wanted to try this circuit,
>>>>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>>>>
>>>>>>>>>   But have not got to it yet, to much computer time and not enough
>>>>>>>>> bench time.
>>>>>>>>>                                        Mikek
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>> The transit time part comes into it like this: due to the electron
>>>>>>>> travel time there is a short delay before grid voltage changes
>>>>>>>> during the positive peaks get to influence the cathode voltage. At
>>>>>>>> very high frequencies this increased loading at the peaks gets more
>>>>>>>> significant.
>>>>>>>>
>>>>>>>> The 535A tube is quite large and looks like it was built for low
>>>>>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>>>>>> like an acorn device may have had shorter delay times.
>>>>>>>>
>>>>>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>>>>
>>>>>>>> piglet
>>>>>>>>
>>>>>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>>>>>                                               Thanks, Mikek
>>>>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>>>>> 50MHz is reactance of 13kohm.
>>>>>  I would think any capacitance just adds to the resonating capacitance,
>>>>> so just need to calculate in the loss of the capacitance, not the
>>>>> capacitance.
>>>>>
>>>>>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>>>>>> lot about behavior at 50MHz?
>>>>>  That is very true, but as the much maligned John Larkin said, "this is
>>>>> a discussion group" so, I'm having the topic discussed!
>>>>>
>>>>> Mikek
>>>> I'm not maligned by anybody that matters. That's by definition.
>>>>
>>>  Agreed and, I looked it up before I used it, I thought it fit well.
>>>
>>> "If you describe someone or something as much-maligned,
>>> you mean that *they are often criticized by people,
>>> but you think the criticism is unfair or exaggerated because they have
>>> good qualities too*."
>>>
>>>   The people that criticize you have a political opinion and they have
>>> to go after you personally
>>> rather than argue their point. That don't like it when you have a good
>>> point, so they malign you.
>>>                                              Mikek
>> Because they can't design electronics.
>>
>Neither can I, but I'm not maligning you!
>
>  btw, I got the 1000 Hz bandpass to work, it was tuned to 1008 Hz.
>I wanted it to use to set the focal point of a parabolic mic.
>  I could not get a clean voltage measurement because of all the other
>environmental sound. I added the 1008 Hz bandpass filter between my
>preamp and amp, then, with an app on my phone that I put across the room,
>I generated a 1008Hz sine wave, and had a very clean,
>stable waveform on my scope. Easy peasy, I moved the mic about 3"
>further away from where I thought the focus was, and doubled the Voltage
>output.
>  4 hrs building the bandpass filter for a 3 minute adjustment!
>  Also, I have never seen this on a parabolic mic, I put a small funnel
>on the mic
>this also increased my output voltage.
>
>   I used a sensitive, low noise AOM-PU5024 mic,
>> https://api.puiaudio.com/file/8a1a7f37-cd74-49b0-81f3-f74090655669.pdf
>
>  A low noise TS-472 preamp,
>
>> https://tinyurl.com/56zv2czx
>
>and this 'very neat' little headphone amp to drive the headphones. 3.7"
>x 2" x 0.5".
>
>> https://www.amazon.com/dp/B07MHRBMBY?psc=1&ref=ppx_yo2ov_dt_b_product_details
>
>Which I was able to tap into the power switch to drive the preamp.
>
>  I used a $19 (slightly scratched, returned) squirrel baffle (16") as
>the parabolic reflector, I can always upgrade to
>a $135 22" parabolic dish, but no.
>  Totally worthless project, but it was fun to figure out.
>
>   Next up, a photochopper replacement for my HP3400A, I finally got a
>schematic, it uses a DG403 and 555 for 90Hz drive signal.
>                                Mikek
>

On 9/30/2022 9:32 AM, John Larkin wrote:
> On Fri, 30 Sep 2022 08:29:07 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/30/2022 12:01 AM, John Larkin wrote:
>>> On Thu, 29 Sep 2022 23:23:18 -0500, amdx <amdx@knology.net> wrote:
>>>
>>>> On 9/29/2022 5:42 PM, John Larkin wrote:
>>>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>>>>>
>>>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>>>>>   On one of the groups I monitor, it was ask if the tube circuit
>>>>>>>>>>>> shown below could be bootstrapped to raise the input impedance,
>>>>>>>>>>>> especially at the higher frequencies where it drops pretty low.
>>>>>>>>>>>> (purpose is to reduce loading on the LC being measured--Q meter)
>>>>>>>>>>>>   Can you give a little detail on how you would implement it? And
>>>>>>>>>>>> what happens to gain and frequency response?
>>>>>>>>>>>> When was bootstrapping introduced, the word started in the 1880s,
>>>>>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>>>>>> I did manage to find a bootstrapped tube circuit, but it didn't
>>>>>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>>>>>> bootstrapping?
>>>>>>>>>>>>   I made my proposed idea on the right side.
>>>>>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>>>>>> bootstrapping help that?
>>>>>>>>>>>>   Might be barking up the wrong tree.
>>>>>>>>>>>>
>>>>>>>>>>>>  >
>>>>>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>>                              Thanks, Mikek
>>>>>>>>>>>>
>>>>>>>>>>> Did you see the value of C302? I think V301 is being used in the
>>>>>>>>>>> so called "infinite impedance" detector configuration. The cathode
>>>>>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>>>>>> level representing something between the peak and average ac
>>>>>>>>>>> input. So AC bootstrapping that circuit not possible. I guess you
>>>>>>>>>>> could insert a whole new hi-z buffer between tuned circuit under
>>>>>>>>>>> test and detector but in practice it would be difficult to get it
>>>>>>>>>>> to be an improvement?
>>>>>>>>>>>
>>>>>>>>>>> piglet
>>>>>>>>>>>
>>>>>>>>>>   I thought I'd seen it referred to as an "infinite impedance
>>>>>>>>>> detector", but don't find it in the manual.
>>>>>>>>>> I do see this line in the manual and don't understand how transit
>>>>>>>>>> time loss in the voltmeter
>>>>>>>>>> tube causes a shunt resistance across the measuring circuit at High
>>>>>>>>>> Frequencies.
>>>>>>>>>> Can someone provide a simple explanation?
>>>>>>>>>>
>>>>>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>>>>>
>>>>>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>>>>>> I always wanted to try this circuit,
>>>>>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>>>>>
>>>>>>>>>>   But have not got to it yet, to much computer time and not enough
>>>>>>>>>> bench time.
>>>>>>>>>>                                        Mikek
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> The transit time part comes into it like this: due to the electron
>>>>>>>>> travel time there is a short delay before grid voltage changes
>>>>>>>>> during the positive peaks get to influence the cathode voltage. At
>>>>>>>>> very high frequencies this increased loading at the peaks gets more
>>>>>>>>> significant.
>>>>>>>>>
>>>>>>>>> The 535A tube is quite large and looks like it was built for low
>>>>>>>>> inter-electrode capacity and low leakage. For VHF use a smaller tube
>>>>>>>>> like an acorn device may have had shorter delay times.
>>>>>>>>>
>>>>>>>>> Looks to me like that bootstrap all nodes fet buffer came straight
>>>>>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>>>>>
>>>>>>>>> piglet
>>>>>>>>>
>>>>>>>>    Yes, it did, but, the question is will it work in place of the tube?
>>>>>>>>                                               Thanks, Mikek
>>>>>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>>>>>> 50MHz is reactance of 13kohm.
>>>>>>  I would think any capacitance just adds to the resonating capacitance,
>>>>>> so just need to calculate in the loss of the capacitance, not the
>>>>>> capacitance.
>>>>>>
>>>>>>> Since your main interest is around 1.5MHz you perhaps needn't worry a
>>>>>>> lot about behavior at 50MHz?
>>>>>>  That is very true, but as the much maligned John Larkin said, "this is
>>>>>> a discussion group" so, I'm having the topic discussed!
>>>>>>
>>>>>> Mikek
>>>>> I'm not maligned by anybody that matters. That's by definition.
>>>>>
>>>>  Agreed and, I looked it up before I used it, I thought it fit well.
>>>>
>>>> "If you describe someone or something as much-maligned,
>>>> you mean that *they are often criticized by people,
>>>> but you think the criticism is unfair or exaggerated because they have
>>>> good qualities too*."
>>>>
>>>>   The people that criticize you have a political opinion and they have
>>>> to go after you personally
>>>> rather than argue their point. That don't like it when you have a good
>>>> point, so they malign you.
>>>>                                              Mikek
>>> Because they can't design electronics.
>>>
>> Neither can I, but I'm not maligning you!
>>
>>  btw, I got the 1000 Hz bandpass to work, it was tuned to 1008 Hz.
>> I wanted it to use to set the focal point of a parabolic mic.
>>  I could not get a clean voltage measurement because of all the other
>> environmental sound. I added the 1008 Hz bandpass filter between my
>> preamp and amp, then, with an app on my phone that I put across the room,
>> I generated a 1008Hz sine wave, and had a very clean,
>> stable waveform on my scope. Easy peasy, I moved the mic about 3"
>> further away from where I thought the focus was, and doubled the Voltage
>> output.
>>  4 hrs building the bandpass filter for a 3 minute adjustment!
>>  Also, I have never seen this on a parabolic mic, I put a small funnel
>> on the mic
>> this also increased my output voltage.
>>
>>   I used a sensitive, low noise AOM-PU5024 mic,
>>> https://api.puiaudio.com/file/8a1a7f37-cd74-49b0-81f3-f74090655669.pdf
>>  A low noise TS-472 preamp,
>>
>>> https://tinyurl.com/56zv2czx
>> and this 'very neat' little headphone amp to drive the headphones. 3.7"
>> x 2" x 0.5".
>>
>>> https://www.amazon.com/dp/B07MHRBMBY?psc=1&ref=ppx_yo2ov_dt_b_product_details
>> Which I was able to tap into the power switch to drive the preamp.
>>
>>  I used a $19 (slightly scratched, returned) squirrel baffle (16") as
>> the parabolic reflector, I can always upgrade to
>> a $135 22" parabolic dish, but no.
>>  Totally worthless project, but it was fun to figure out.
>>
>>   Next up, a photochopper replacement for my HP3400A, I finally got a
>> schematic, it uses a DG403 and 555 for 90Hz drive signal.
>>                                Mikek
>>
> There are some great optocoupled solid-state relays around. The input
> side is LEDs and the output is mosfets, zero offset voltage.
>
  The H11F1M has been used, but I didn't get a schematic for it. I
don't expect much
in the way of a circuit required. I was disappointed it doesn't come in
a quad.
 If there is a second round I might try it.
                     Mikek

On 9/30/2022 11:06 AM, Anthony William Sloman wrote:
> On Friday, September 30, 2022 at 8:42:58 AM UTC+10, John Larkin wrote:
>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <am...@knology.net> wrote:
>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>> On 24/09/2022 13:44, amdx wrote:
>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>> That is very true, but as the much maligned John Larkin said, "this is
>>> a discussion group" so, I'm having the topic discussed!
>> I'm not maligned by anybody that matters. That's by definition.
> Nobody who won't flatter John Larkin matters to John Larkin.
>
> The climate change denial propaganda lobby flatters everybody who is silly enough to read their output, so John Larkin takes them very seriously, and pointing this out is maligning him. He probably ought to re-work his definitions but he's much too addicted to getting flattered for this to be likely to happen.
>
 The lead antagonist chimes in with more personal attacks. Nothing
changes for the libs,
they hate conservatives, while conservatives just think the libs have it
wrong.
                             Mikek

On 9/30/2022 11:45 AM, amdx wrote:
> On 9/30/2022 9:32 AM, John Larkin wrote:
>> On Fri, 30 Sep 2022 08:29:07 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/30/2022 12:01 AM, John Larkin wrote:
>>>> On Thu, 29 Sep 2022 23:23:18 -0500, amdx <amdx@knology.net> wrote:
>>>>
>>>>> On 9/29/2022 5:42 PM, John Larkin wrote:
>>>>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <amdx@knology.net> wrote:
>>>>>>
>>>>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>>>>>>>>      On one of the groups I monitor, it was ask if the
>>>>>>>>>>>>> tube circuit
>>>>>>>>>>>>> shown below could be bootstrapped to raise the input
>>>>>>>>>>>>> impedance,
>>>>>>>>>>>>> especially at the higher frequencies where it drops pretty
>>>>>>>>>>>>> low.
>>>>>>>>>>>>> (purpose is to reduce loading on the LC being measured--Q
>>>>>>>>>>>>> meter)
>>>>>>>>>>>>>      Can you give a little detail on how you would
>>>>>>>>>>>>> implement it? And
>>>>>>>>>>>>> what happens to gain and frequency response?
>>>>>>>>>>>>> When was bootstrapping introduced, the word started in the
>>>>>>>>>>>>> 1880s,
>>>>>>>>>>>>> but when was it first used in an electrical circuit?
>>>>>>>>>>>>> I did manage to find a bootstrapped tube circuit, but it
>>>>>>>>>>>>> didn't
>>>>>>>>>>>>> use a 100M? grid resistor, Is that a detriment to adding
>>>>>>>>>>>>> bootstrapping?
>>>>>>>>>>>>>      I made my proposed idea on the right side.
>>>>>>>>>>>>> Hmm, the problem is more the tube input than the 100M?, does
>>>>>>>>>>>>> bootstrapping help that?
>>>>>>>>>>>>>      Might be barking up the wrong tree.
>>>>>>>>>>>>>
>>>>>>>>>>>>>     >
>>>>>>>>>>>>> https://www.dropbox.com/s/in6no3nvw0qnie7/Boonton%20260A%20Tube%20bootstrap%20question.jpg?dl=0
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>                                 Thanks, Mikek
>>>>>>>>>>>>>
>>>>>>>>>>>> Did you see the value of C302? I think V301 is being used
>>>>>>>>>>>> in the
>>>>>>>>>>>> so called "infinite impedance" detector configuration. The
>>>>>>>>>>>> cathode
>>>>>>>>>>>> voltage is not the buffered grid ac input but instead is a dc
>>>>>>>>>>>> level representing something between the peak and average ac
>>>>>>>>>>>> input. So AC bootstrapping that circuit not possible. I
>>>>>>>>>>>> guess you
>>>>>>>>>>>> could insert a whole new hi-z buffer between tuned circuit
>>>>>>>>>>>> under
>>>>>>>>>>>> test and detector but in practice it would be difficult to
>>>>>>>>>>>> get it
>>>>>>>>>>>> to be an improvement?
>>>>>>>>>>>>
>>>>>>>>>>>> piglet
>>>>>>>>>>>>
>>>>>>>>>>>      I thought I'd seen it referred to as an "infinite
>>>>>>>>>>> impedance
>>>>>>>>>>> detector", but don't find it in the manual.
>>>>>>>>>>> I do see this line in the manual and don't understand how
>>>>>>>>>>> transit
>>>>>>>>>>> time loss in the voltmeter
>>>>>>>>>>> tube causes a shunt resistance across the measuring circuit
>>>>>>>>>>> at High
>>>>>>>>>>> Frequencies.
>>>>>>>>>>> Can someone provide a simple explanation?
>>>>>>>>>>>
>>>>>>>>>>> "QVOLTMETERCONDUCTANCE.
>>>>>>>>>>> Anotherinternalparameterwhich causestheindi-
>>>>>>>>>>> catedQtodeviatefromeffectiveQ,atbothvery low
>>>>>>>>>>> andveryhighfrequencies, is theinputconductanceof
>>>>>>>>>>> theQvoltmeter circuit.Atvery low frequenciesthis
>>>>>>>>>>> conductance consistsofa 100megohmgridleak resistor
>>>>>>>>>>> inparallelwiththeinternallossesofthevacuum tube.
>>>>>>>>>>> Atveryhighfrequenciesthetransittime lossinthevolt-
>>>>>>>>>>> metertubeshuntstheresonatingcapacitorandintro-
>>>>>>>>>>> duces ashuntresistance acrossthemeasuring circuit"
>>>>>>>>>>>
>>>>>>>>>>> Someone has developed a single fet circuit that does an OK job.
>>>>>>>>>>> I always wanted to try this circuit,
>>>>>>>>>>>> https://www.dropbox.com/s/wvwkw2iapf4ufd7/High%20impedance%20input.jpg?dl=0
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>      But have not got to it yet, to much computer time and
>>>>>>>>>>> not enough
>>>>>>>>>>> bench time.
>>>>>>>>>>> Mikek
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>> The transit time part comes into it like this: due to the
>>>>>>>>>> electron
>>>>>>>>>> travel time there is a short delay before grid voltage changes
>>>>>>>>>> during the positive peaks get to influence the cathode
>>>>>>>>>> voltage. At
>>>>>>>>>> very high frequencies this increased loading at the peaks
>>>>>>>>>> gets more
>>>>>>>>>> significant.
>>>>>>>>>>
>>>>>>>>>> The 535A tube is quite large and looks like it was built for low
>>>>>>>>>> inter-electrode capacity and low leakage. For VHF use a
>>>>>>>>>> smaller tube
>>>>>>>>>> like an acorn device may have had shorter delay times.
>>>>>>>>>>
>>>>>>>>>> Looks to me like that bootstrap all nodes fet buffer came
>>>>>>>>>> straight
>>>>>>>>>> out of a late 1960s-early 70s NatSemi app note.
>>>>>>>>>>
>>>>>>>>>> piglet
>>>>>>>>>>
>>>>>>>>>       Yes, it did, but, the question is will it work in place
>>>>>>>>> of the tube?
>>>>>>>>> Thanks, Mikek
>>>>>>>> The touted capacitance of the bootstrapped fet is 0.25pF which at
>>>>>>>> 50MHz is reactance of 13kohm.
>>>>>>>     I would think any capacitance just adds to the resonating
>>>>>>> capacitance,
>>>>>>> so just need to calculate in the loss of the capacitance, not the
>>>>>>> capacitance.
>>>>>>>
>>>>>>>> Since your main interest is around 1.5MHz you perhaps needn't
>>>>>>>> worry a
>>>>>>>> lot about behavior at 50MHz?
>>>>>>>     That is very true, but as the much maligned John Larkin
>>>>>>> said, "this is
>>>>>>> a discussion group" so, I'm having the topic discussed!
>>>>>>>
>>>>>>> Mikek
>>>>>> I'm not maligned by anybody that matters. That's by definition.
>>>>>>
>>>>>    Agreed and, I looked it up before I used it, I thought it fit
>>>>> well.
>>>>>
>>>>> "If you describe someone or something as much-maligned,
>>>>> you mean that *they are often criticized by people,
>>>>> but you think the criticism is unfair or exaggerated because they
>>>>> have
>>>>> good qualities too*."
>>>>>
>>>>>     The people that criticize you have a political opinion and
>>>>> they have
>>>>> to go after you personally
>>>>> rather than argue their point. That don't like it when you have a
>>>>> good
>>>>> point, so they malign you.
>>>>>                                                Mikek
>>>> Because they can't design electronics.
>>>>
>>> Neither can I, but I'm not maligning you!
>>>
>>>   btw, I got the 1000 Hz bandpass to work, it was tuned to 1008 Hz.
>>> I wanted it to use to set the focal point of a parabolic mic.
>>>   I could not get a clean voltage measurement because of all the other
>>> environmental sound. I added the 1008 Hz bandpass filter between my
>>> preamp and amp, then, with an app on my phone that I put across the
>>> room,
>>> I generated a 1008Hz sine wave, and had a very clean,
>>> stable waveform on my scope. Easy peasy, I moved the mic about 3"
>>> further away from where I thought the focus was, and doubled the
>>> Voltage
>>> output.
>>>   4 hrs building the bandpass filter for a 3 minute adjustment!
>>>   Also, I have never seen this on a parabolic mic, I put a small funnel
>>> on the mic
>>> this also increased my output voltage.
>>>
>>>    I used a sensitive, low noise AOM-PU5024 mic,
>>>> https://api.puiaudio.com/file/8a1a7f37-cd74-49b0-81f3-f74090655669.pdf
>>>   A low noise TS-472 preamp,
>>>
>>>> https://tinyurl.com/56zv2czx
>>> and this 'very neat' little headphone amp to drive the headphones. 3.7"
>>> x 2" x 0.5".
>>>
>>>> https://www.amazon.com/dp/B07MHRBMBY?psc=1&ref=ppx_yo2ov_dt_b_product_details
>>>>
>>> Which I was able to tap into the power switch to drive the preamp.
>>>
>>>   I used a $19 (slightly scratched, returned) squirrel baffle (16") as
>>> the parabolic reflector, I can always upgrade to
>>> a $135 22" parabolic dish, but no.
>>>   Totally worthless project, but it was fun to figure out.
>>>
>>>    Next up, a photochopper replacement for my HP3400A, I finally got a
>>> schematic, it uses a DG403 and 555 for 90Hz drive signal.
>>>                                 Mikek
>>>
>> There are some great optocoupled solid-state relays around. The input
>> side is LEDs and the output is mosfets, zero offset voltage.
>>
>   The H11F1M has been used, but I didn't get a schematic for it. I
> don't expect much
> in the way of a circuit required. I was disappointed it doesn't come
> in a quad.
>  If there is a second round I might try it.
>                      Mikek
 Also an AD7510D has been used for the switches.
                                    Mikek

On Friday, September 30, 2022 at 9:48:24 AM UTC-7, amdx wrote:

> The lead antagonist chimes in with more personal attacks. Nothing
> changes for the libs,
> they hate conservatives, while conservatives just think the libs have it
> wrong.

Expressions of hate can follow from falsities and evasions inserted into dialog.
Expressions of contempt can be covered by apologetic 'the libs have it wrong'.

Expressions of both types are blockage of useful discussion of policies
that we require for functional democracy. Neither is productive, and
if it interferes with politics, is to be deplored.

Newt Gingrich shows us the problem; Gandhi shows us the solution.

On Fri, 30 Sep 2022 11:48:17 -0500, amdx <amdx@knology.net> wrote:

>On 9/30/2022 11:06 AM, Anthony William Sloman wrote:
>> On Friday, September 30, 2022 at 8:42:58 AM UTC+10, John Larkin wrote:
>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <am...@knology.net> wrote:
>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>> That is very true, but as the much maligned John Larkin said, "this is
>>>> a discussion group" so, I'm having the topic discussed!
>>> I'm not maligned by anybody that matters. That's by definition.
>> Nobody who won't flatter John Larkin matters to John Larkin.
>>
>> The climate change denial propaganda lobby flatters everybody who is silly enough to read their output, so John Larkin takes them very seriously, and pointing this out is maligning him. He probably ought to re-work his definitions but he's much too addicted to getting flattered for this to be likely to happen.
>>
>  The lead antagonist chimes in with more personal attacks. Nothing
>changes for the libs,
>they hate conservatives, while conservatives just think the libs have it
>wrong.
>                              Mikek

Sloman is a droning insult machine. He hasn't designed electronics in
decades, and previous attempts seem to have been failures.

Yes, liberals usually don't understand how systems work, so mess them
up. They hate people who do understand.

amdx wrote:
> On 9/30/2022 11:06 AM, Anthony William Sloman wrote:
>> On Friday, September 30, 2022 at 8:42:58 AM UTC+10, John Larkin wrote:
>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <am...@knology.net> wrote:
>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>   That is very true, but as the much maligned John Larkin said,
>>>> "this is
>>>> a discussion group" so, I'm having the topic discussed!
>>> I'm not maligned by anybody that matters. That's by definition.
>> Nobody who won't flatter John Larkin matters to John Larkin.
>>
>> The climate change denial propaganda lobby flatters everybody who is
>> silly enough to read their output, so John Larkin takes them very
>> seriously, and pointing this out is maligning him. He probably ought
>> to re-work his definitions but he's much too addicted to getting
>> flattered for this to be likely to happen.
>>
>  The lead antagonist chimes in with more personal attacks. Nothing
> changes for the libs,
> they hate conservatives, while conservatives just think the libs have it
> wrong.
>                              Mikek

_And_ have cooties. ;)

On Fri, 30 Sep 2022 13:28:46 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>amdx wrote:
>> On 9/30/2022 11:06 AM, Anthony William Sloman wrote:
>>> On Friday, September 30, 2022 at 8:42:58 AM UTC+10, John Larkin wrote:
>>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <am...@knology.net> wrote:
>>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>   That is very true, but as the much maligned John Larkin said,
>>>>> "this is
>>>>> a discussion group" so, I'm having the topic discussed!
>>>> I'm not maligned by anybody that matters. That's by definition.
>>> Nobody who won't flatter John Larkin matters to John Larkin.
>>>
>>> The climate change denial propaganda lobby flatters everybody who is
>>> silly enough to read their output, so John Larkin takes them very
>>> seriously, and pointing this out is maligning him. He probably ought
>>> to re-work his definitions but he's much too addicted to getting
>>> flattered for this to be likely to happen.
>>>
>>  The lead antagonist chimes in with more personal attacks. Nothing
>> changes for the libs,
>> they hate conservatives, while conservatives just think the libs have it
>> wrong.
>>                              Mikek
>
>_And_ have cooties. ;)

Of sex, drugs, and rock-and-roll, at least two turned out to be
dangerous.

On 9/30/2022 3:18 PM, John Larkin wrote:
> On Fri, 30 Sep 2022 13:28:46 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> amdx wrote:
>>> On 9/30/2022 11:06 AM, Anthony William Sloman wrote:
>>>> On Friday, September 30, 2022 at 8:42:58 AM UTC+10, John Larkin wrote:
>>>>> On Tue, 27 Sep 2022 12:46:28 -0500, amdx <am...@knology.net> wrote:
>>>>>> On 9/27/2022 3:59 AM, piglet wrote:
>>>>>>> On 24/09/2022 13:44, amdx wrote:
>>>>>>>> On 9/24/2022 6:47 AM, piglet wrote:
>>>>>>>>> On 24/09/2022 11:58, amdx wrote:
>>>>>>>>>> On 9/24/2022 1:11 AM, piglet wrote:
>>>>>>>>>>> On 24/09/2022 00:33, amdx wrote:
>>>>>>   That is very true, but as the much maligned John Larkin said,
>>>>>> "this is
>>>>>> a discussion group" so, I'm having the topic discussed!
>>>>> I'm not maligned by anybody that matters. That's by definition.
>>>> Nobody who won't flatter John Larkin matters to John Larkin.
>>>>
>>>> The climate change denial propaganda lobby flatters everybody who is
>>>> silly enough to read their output, so John Larkin takes them very
>>>> seriously, and pointing this out is maligning him. He probably ought
>>>> to re-work his definitions but he's much too addicted to getting
>>>> flattered for this to be likely to happen.
>>>>
>>>  The lead antagonist chimes in with more personal attacks. Nothing
>>> changes for the libs,
>>> they hate conservatives, while conservatives just think the libs have it
>>> wrong.
>>>                              Mikek
>> _And_ have cooties. ;)
> Of sex, drugs, and rock-and-roll, at least two turned out to be
> dangerous.
>
Well, Tipper Gore thought rock-and-roll was dangerous and with Aids/STDs
making sex dangerous,
that leaves drugs. But then the worst neighbor I ever had sold a house
he didn't own and with
that pile of money found enough Fentynal to leave that pile of money to
his son!
                               Mikek

On Friday, September 30, 2022 at 1:01:27 AM UTC-4, John Larkin wrote:
>
> Because they can't design electronics.

Some of us do design work with 97% less bragging. Verified by independent testing!

--

Rick C.

+ Get 1,000 miles of free Supercharging
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