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

On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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

The bootstrap would reduce the R201 loading a bit but I doubt it would
improve Q measurement much.

The loading of V301 probably dominates.

Are you trying to measure super high Qs?

I built a Q-meter

https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1

https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1

I used resonance width, rather than voltage multiplication.

I didn't have any black wrinkle paint to finish it off.

On 9/23/2022 7:05 PM, John Larkin wrote:
> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
> The bootstrap would reduce the R201 loading a bit but I doubt it would
> improve Q measurement much.
>
> The loading of V301 probably dominates.
>
> Are you trying to measure super high Qs?
>
> I built a Q-meter
>
> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>
> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>
> I used resonance width, rather than voltage multiplication.
>
> I didn't have any black wrinkle paint to finish it off.
>
 Just following along on an IO Group in a discussion about designing a
Q meter.
Looking at the Boonton 260A and the HP 4342A for ideas and then
someone ask about bootstrapping the tube in the 260A, so I thought I'd
ask here.
  Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
turns per inch, just to see where
the sweet spot was. One peaked close to 1400Q.
   I wound a ferrite rod a couple days ago and it measured 1236Q at
800kHz.
I think someone questioned that number and they wound one on the same
material, and theirs peaked at 1326Q.
The material is very low loss in the AM band, R40C1.
 Also some interesting discussion on 50 to 1 injection transformers
driven by low impedance amps.
Here's the beginning, but you need to start at the bottom of the the
page for the first post and page up to follow.
> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1

                                 Mikek

On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:

>On 9/23/2022 7:05 PM, John Larkin wrote:
>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>> improve Q measurement much.
>>
>> The loading of V301 probably dominates.
>>
>> Are you trying to measure super high Qs?
>>
>> I built a Q-meter
>>
>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>
>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>
>> I used resonance width, rather than voltage multiplication.
>>
>> I didn't have any black wrinkle paint to finish it off.
>>
>  Just following along on an IO Group in a discussion about designing a
>Q meter.
>Looking at the Boonton 260A and the HP 4342A for ideas and then
>someone ask about bootstrapping the tube in the 260A, so I thought I'd
>ask here.
>   Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>turns per inch, just to see where
>the sweet spot was. One peaked close to 1400Q.
>    I wound a ferrite rod a couple days ago and it measured 1236Q at
>800kHz.
>I think someone questioned that number and they wound one on the same
>material, and theirs peaked at 1326Q.
>The material is very low loss in the AM band, R40C1.
>  Also some interesting discussion on 50 to 1 injection transformers
>driven by low impedance amps.
>Here's the beginning, but you need to start at the bottom of the the
>page for the first post and page up to follow.
>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>
>
>                                  Mikek

When the old Boonton was designed, it was hard to generate and
precisely measure frequencies. Now it's easy. So resonant width is a
good way to measure Q.

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

On 9/23/2022 11:20 PM, John Larkin wrote:
> On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/23/2022 7:05 PM, John Larkin wrote:
>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>>> improve Q measurement much.
>>>
>>> The loading of V301 probably dominates.
>>>
>>> Are you trying to measure super high Qs?
>>>
>>> I built a Q-meter
>>>
>>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>>
>>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>>
>>> I used resonance width, rather than voltage multiplication.
>>>
>>> I didn't have any black wrinkle paint to finish it off.
>>>
>>  Just following along on an IO Group in a discussion about designing a
>> Q meter.
>> Looking at the Boonton 260A and the HP 4342A for ideas and then
>> someone ask about bootstrapping the tube in the 260A, so I thought I'd
>> ask here.
>>   Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>> turns per inch, just to see where
>> the sweet spot was. One peaked close to 1400Q.
>>    I wound a ferrite rod a couple days ago and it measured 1236Q at
>> 800kHz.
>> I think someone questioned that number and they wound one on the same
>> material, and theirs peaked at 1326Q.
>> The material is very low loss in the AM band, R40C1.
>>  Also some interesting discussion on 50 to 1 injection transformers
>> driven by low impedance amps.
>> Here's the beginning, but you need to start at the bottom of the the
>> page for the first post and page up to follow.
>>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>>
>>                                  Mikek
> When the old Boonton was designed, it was hard to generate and
> precisely measure frequencies. Now it's easy. So resonant width is a
> good way to measure Q.
>
  Yes. I have done a lot of that, but all I had was a scope for amplitude.
So, after too many BW tests, I came up with 5 / 7 = 0.714, that is close
enough
for relative measurements using a scope. So, I would set Fr at 7 units,
adjusting either
the freq gen amplitude or scope CAL, then raise/lower the frequency
until I had 5 units.
At that the time about 30 years ago, I was sorting piezo discs with Qs
over 1200 for the highest Q.
We only used the highest Q discs to bond for our transducers.
 I ask this on another group and never got an answer,
"Is it possible to come up with a formula or spreadsheet that would
calculate Q from 3db BW,
with the caveat that instead of using 0.707, use the number 0.7 and
normalize it to 3db?
That would be great for needle type meters. For oscilloscopes, I'd like
to see
0.714 normalized to 3db, why because I like to peak at 7 units and
raise/lower the frequency to 5 units.
5 / 7 = 0.714.
       Mikek

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

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

at very high frequencies the electron time delay

On 24/09/2022 11:33, amdx wrote:
> On 9/23/2022 11:20 PM, John Larkin wrote:
>> On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/23/2022 7:05 PM, John Larkin wrote:
>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>>>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>>>> improve Q measurement much.
>>>>
>>>> The loading of V301 probably dominates.
>>>>
>>>> Are you trying to measure super high Qs?
>>>>
>>>> I built a Q-meter
>>>>
>>>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>>>
>>>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>>>
>>>> I used resonance width, rather than voltage multiplication.
>>>>
>>>> I didn't have any black wrinkle paint to finish it off.
>>>>
>>>   Just following along on an IO Group in a discussion about designing a
>>> Q meter.
>>> Looking at the Boonton 260A and the HP 4342A for ideas and then
>>> someone ask about bootstrapping the tube in the 260A, so I thought I'd
>>> ask here.
>>>    Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>>> turns per inch, just to see where
>>> the sweet spot was. One peaked close to 1400Q.
>>>     I wound a ferrite rod a couple days ago and it measured 1236Q at
>>> 800kHz.
>>> I think someone questioned that number and they wound one on the same
>>> material, and theirs peaked at 1326Q.
>>> The material is very low loss in the AM band, R40C1.
>>>   Also some interesting discussion on 50 to 1 injection transformers
>>> driven by low impedance amps.
>>> Here's the beginning, but you need to start at the bottom of the the
>>> page for the first post and page up to follow.
>>>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>>>>
>>>
>>>                                   Mikek
>> When the old Boonton was designed, it was hard to generate and
>> precisely measure frequencies. Now it's easy. So resonant width is a
>> good way to measure Q.
>>
>   Yes. I have done a lot of that, but all I had was a scope for amplitude.
> So, after too many BW tests, I came up with 5 / 7 = 0.714, that is close
> enough
> for relative measurements using a scope. So, I would set Fr at 7 units,
> adjusting either
> the freq gen amplitude or scope CAL, then raise/lower the frequency
> until I had 5 units.
> At that the time about 30 years ago, I was sorting piezo discs with Qs
> over 1200 for the highest Q.
> We only used the highest Q discs to bond for our transducers.
>  I ask this on another group and never got an answer,
> "Is it possible to come up with a formula or spreadsheet that would
> calculate Q from 3db BW,
> with the caveat that instead of using 0.707, use the number 0.7 and
> normalize it to 3db?
> That would be great for needle type meters. For oscilloscopes, I'd like
> to see
> 0.714 normalized to 3db, why because I like to peak at 7 units and
> raise/lower the frequency to 5 units.
> 5 / 7 = 0.714.
>        Mikek

If that were me I'd use either 0.7 or 0.714 but be consistent and just
the same method everytime. Good enough for comparative evaluation of
coils and both are within 1% of 0.707 and anyhow Q is such a tricky
parameter to nail down consistently.

piglet

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

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

It will work as a buffer ahead of the tube. Or indeed in front of any
other detector/rectifier. You cannot make an infinite impedance detector
with bootstrapped input in one go - gotta have something to drive the
bootstrap!

piglet

>> "Is it possible to come up with a formula or spreadsheet that would
>> calculate Q from 3db BW,

B = f0 / Q
where
B is the 3 dB bandwidth
f0 is the center frequency

So Q = f0 / B

So for example 100 kHz bandwidth at 1 MHz makes a Q of 10.

On 9/24/2022 10:30 AM, Jan Panteltje wrote:
>>> "Is it possible to come up with a formula or spreadsheet that would
>>> calculate Q from 3db BW,
> B = f0 / Q
> where
> B is the 3 dB bandwidth
> f0 is the center frequency
>
> So Q = f0 / B
>
> So for example 100 kHz bandwidth at 1 MHz makes a Q of 10.
>
 Yes, I got that part, what I wanted is to normalize 0.7 and 0.714
voltage levels
to 3db. But as piglet said, it is a very small error, so fagetaboutit.
Unless you want to do the math and tell me multiply by xxx to get the
3db BW.

The question as posed,

"Is it possible to come up with a formula or spreadsheet that would
calculate Q from 3db BW,  edit: hmm, poorly worded
with the caveat that instead of using 0.707, use the number 0.7 and
normalize it to 3db?
That would be great for needle type meters. For oscilloscopes, I'd like
to see
0.714 normalized to 3db, why because I like to peak at 7 units and
raise/lower the frequency to 5 units.
5 / 7 = 0.714.                                Mikek

On Sat, 24 Sep 2022 11:27:42 -0500, amdx <amdx@knology.net> wrote:

>On 9/24/2022 10:30 AM, Jan Panteltje wrote:
>>>> "Is it possible to come up with a formula or spreadsheet that would
>>>> calculate Q from 3db BW,
>> B = f0 / Q
>> where
>> B is the 3 dB bandwidth
>> f0 is the center frequency
>>
>> So Q = f0 / B
>>
>> So for example 100 kHz bandwidth at 1 MHz makes a Q of 10.
>>
>  Yes, I got that part, what I wanted is to normalize 0.7 and 0.714
>voltage levels
>to 3db. But as piglet said, it is a very small error, so fagetaboutit.
>Unless you want to do the math and tell me multiply by xxx to get the
>3db BW.

There is a simple fudge factor. Spice will show what it is.

You can also fudge for a finite source resistance in the signal
source, which matters only for very high Qs.

The other way to measure Q is to drive a series LC from a 50 ohm
signal generator, series resonate, and scope the input voltage. Be
careful about harmonics.

John Larkin wrote:
> On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/23/2022 7:05 PM, John Larkin wrote:
>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>>> improve Q measurement much.
>>>
>>> The loading of V301 probably dominates.
>>>
>>> Are you trying to measure super high Qs?
>>>
>>> I built a Q-meter
>>>
>>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>>
>>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>>
>>> I used resonance width, rather than voltage multiplication.
>>>
>>> I didn't have any black wrinkle paint to finish it off.
>>>
>>  Just following along on an IO Group in a discussion about designing a
>> Q meter.
>> Looking at the Boonton 260A and the HP 4342A for ideas and then
>> someone ask about bootstrapping the tube in the 260A, so I thought I'd
>> ask here.
>>   Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>> turns per inch, just to see where
>> the sweet spot was. One peaked close to 1400Q.
>>    I wound a ferrite rod a couple days ago and it measured 1236Q at
>> 800kHz.
>> I think someone questioned that number and they wound one on the same
>> material, and theirs peaked at 1326Q.
>> The material is very low loss in the AM band, R40C1.
>>  Also some interesting discussion on 50 to 1 injection transformers
>> driven by low impedance amps.
>> Here's the beginning, but you need to start at the bottom of the the
>> page for the first post and page up to follow.
>>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>>
>>
>>                                  Mikek
>
> When the old Boonton was designed, it was hard to generate and
> precisely measure frequencies. Now it's easy. So resonant width is a
> good way to measure Q.
>

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

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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.

On Sun, 25 Sep 2022 13:55:44 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>John Larkin wrote:
>> On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/23/2022 7:05 PM, John Larkin wrote:
>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>>>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>>>> improve Q measurement much.
>>>>
>>>> The loading of V301 probably dominates.
>>>>
>>>> Are you trying to measure super high Qs?
>>>>
>>>> I built a Q-meter
>>>>
>>>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>>>
>>>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>>>
>>>> I used resonance width, rather than voltage multiplication.
>>>>
>>>> I didn't have any black wrinkle paint to finish it off.
>>>>
>>>  Just following along on an IO Group in a discussion about designing a
>>> Q meter.
>>> Looking at the Boonton 260A and the HP 4342A for ideas and then
>>> someone ask about bootstrapping the tube in the 260A, so I thought I'd
>>> ask here.
>>>   Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>>> turns per inch, just to see where
>>> the sweet spot was. One peaked close to 1400Q.
>>>    I wound a ferrite rod a couple days ago and it measured 1236Q at
>>> 800kHz.
>>> I think someone questioned that number and they wound one on the same
>>> material, and theirs peaked at 1326Q.
>>> The material is very low loss in the AM band, R40C1.
>>>  Also some interesting discussion on 50 to 1 injection transformers
>>> driven by low impedance amps.
>>> Here's the beginning, but you need to start at the bottom of the the
>>> page for the first post and page up to follow.
>>>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>>>
>>>
>>>                                  Mikek
>>
>> When the old Boonton was designed, it was hard to generate and
>> precisely measure frequencies. Now it's easy. So resonant width is a
>> good way to measure Q.
>>
>
>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

An R-L-C goes to unity gain at low frequencies, which suggests Q=1 by
the simple voltage multiplier formula, for any R.

Or Q goes to zero if the L is the grounded part.

Q is a crude way to collapse the actual impedances. I use it to select
parts for LC oscillators, where it does correlate to spectral purity
and jitter.

Coaxial ceramic resonators get into the thousands, 10's of thousands
sometimes, but are not well suited to my oscillators; equivalent
txline impedances are too low.

John Larkin wrote:
> On Sun, 25 Sep 2022 13:55:44 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> John Larkin wrote:
>>> On Fri, 23 Sep 2022 22:53:43 -0500, amdx <amdx@knology.net> wrote:
>>>
>>>> On 9/23/2022 7:05 PM, John Larkin wrote:
>>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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
>>>>> The bootstrap would reduce the R201 loading a bit but I doubt it would
>>>>> improve Q measurement much.
>>>>>
>>>>> The loading of V301 probably dominates.
>>>>>
>>>>> Are you trying to measure super high Qs?
>>>>>
>>>>> I built a Q-meter
>>>>>
>>>>> https://www.dropbox.com/s/ycd8ya9kwit8o0y/Q-meter.jpg?raw=1
>>>>>
>>>>> https://www.dropbox.com/s/b4xwf1g2ldk0bfl/Q.JPG?raw=1
>>>>>
>>>>> I used resonance width, rather than voltage multiplication.
>>>>>
>>>>> I didn't have any black wrinkle paint to finish it off.
>>>>>
>>>>  Just following along on an IO Group in a discussion about designing a
>>>> Q meter.
>>>> Looking at the Boonton 260A and the HP 4342A for ideas and then
>>>> someone ask about bootstrapping the tube in the 260A, so I thought I'd
>>>> ask here.
>>>>   Several years ago I made five 6" coils with 8, 9, 10, 12, and 13
>>>> turns per inch, just to see where
>>>> the sweet spot was. One peaked close to 1400Q.
>>>>    I wound a ferrite rod a couple days ago and it measured 1236Q at
>>>> 800kHz.
>>>> I think someone questioned that number and they wound one on the same
>>>> material, and theirs peaked at 1326Q.
>>>> The material is very low loss in the AM band, R40C1.
>>>>  Also some interesting discussion on 50 to 1 injection transformers
>>>> driven by low impedance amps.
>>>> Here's the beginning, but you need to start at the bottom of the the
>>>> page for the first post and page up to follow.
>>>>> https://groups.io/g/Test-Equipment-Design-Construction/topic/making_a_q_meter/92809585?p=Created%2C%2C%2C20%2C2%2C200%2C0&jump=1
>>>>
>>>>
>>>>                                  Mikek
>>>
>>> When the old Boonton was designed, it was hard to generate and
>>> precisely measure frequencies. Now it's easy. So resonant width is a
>>> good way to measure Q.
>>>
>>
>> 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
>
> An R-L-C goes to unity gain at low frequencies, which suggests Q=1 by
> the simple voltage multiplier formula, for any R.
>
> Or Q goes to zero if the L is the grounded part.
>
> Q is a crude way to collapse the actual impedances. I use it to select
> parts for LC oscillators, where it does correlate to spectral purity
> and jitter.
>
> Coaxial ceramic resonators get into the thousands, 10's of thousands
> sometimes, but are not well suited to my oscillators; equivalent
> txline impedances are too low.

'Q' is a bit like 'baseband'--useful but not too clearly defined.

For low-loss systems, the calculated

f0 = 1/(2 pi sqrt(LC))

gives, to decent accuracy,

(1) the position of the peak of the Z(f) curve,
(2) the frequency where the impedance of a tank circuit is purely
resistive, and
(3) the average frequency of the free ringdown waveform.

Similarly, and for much the same reason,

Q = 1/(2 pi f_0 R_s C)
= 2 pi f_0 L/R_s
= 1/logarithmic decrement of the free ringing, per cycle
= FWHM / f_0.

For a tank circuit, series and parallel resistances produce equivalent
loss when

R_p = (1 + Q**2) R_s.

All of these hold for high Q, but none of them at low Q. The
discrepancies tend to go like 1/Q**2, so you have to start paying
attention as Q goes below about 10.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 9/25/2022 3:22 PM, John Larkin wrote:
> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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.

On Sun, 25 Sep 2022 21:37:54 -0500, amdx <amdx@knology.net> wrote:

>On 9/25/2022 3:22 PM, John Larkin wrote:
>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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.

On a sunny day (Sun, 25 Sep 2022 13:45:38 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<u1f1jh5qhhu1nkhuf672fhktf90q97vi9g@4ax.com>:

>An R-L-C goes to unity gain at low frequencies, which suggests Q=1 by
>the simple voltage multiplier formula, for any R.
>
>Or Q goes to zero if the L is the grounded part.
>
>Q is a crude way to collapse the actual impedances. I use it to select
>parts for LC oscillators, where it does correlate to spectral purity
>and jitter.

I have used parallel resistors in about 30 MHz circuits (TV IF etc) to reduce Q and
increase bandwidth.

As Q is also w.L / R there is room to play and think about things.
Staggered tuning is an other way to increase bandwidth, bandfilters is an interesting playground.
For an LC I keep C at 220 pF between about .5 MHz and 50 MHz.
For lower frequencies bigger C, for higher smaller.
Always works
Remember old AM radios with 500 pF tuning capacitors?
Those often had longwave and shortwave too.
For FM radio, about 100 MHz, there was a separate section on the tuning capacitor with less capacitance,
For TV UHF tuners even smaller tuning capacitors and some sort of cavities with striplines.

Designed and build all that myself...
becomes sort of a second nature, even TV IF, color circuits, etc.

>Coaxial ceramic resonators get into the thousands, 10's of thousands
>sometimes, but are not well suited to my oscillators; equivalent
>txline impedances are too low.

Crystal filters is an other interesting thing , 9 MHz SSB crystal filters were common in projects.
in the sixties....
Nowadays with software defined radio.... RTL-SDR sticks...
world has changed, in a way got simpler (if you can code)
But when nukes hit and no more chips for whatever reason, that old knowledge can become very handy to sent and receive SOS
or 'we are still alive here'.

Good old RSGB Ham radio handbook from the sixties recommended!

The guy is working with tubes after all!

But a reality check on precision in Q measurements is indeed a good idea
Anything 10% or less is probably good,

On 9/25/2022 10:49 PM, John Larkin wrote:
> On Sun, 25 Sep 2022 21:37:54 -0500, amdx <amdx@knology.net> wrote:
>
>> On 9/25/2022 3:22 PM, John Larkin wrote:
>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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

On Mon, 26 Sep 2022 06:24:15 -0500, amdx <amdx@knology.net> wrote:

>On 9/25/2022 10:49 PM, John Larkin wrote:
>> On Sun, 25 Sep 2022 21:37:54 -0500, amdx <amdx@knology.net> wrote:
>>
>>> On 9/25/2022 3:22 PM, John Larkin wrote:
>>>> On Fri, 23 Sep 2022 18:33:05 -0500, amdx <amdx@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

The 260A design was early 1950s. Big parts, hand wired, lots of
switches, lots of skin loss.

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.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

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 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.
>

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.

57kohm loading at 50MHz is amazingly good for 70 years ago and pretty
respectable still.

piglet