Hello all,

I return with yet more aerial related questions.

The radio next to me has an AM radio with reception from 522 kHz to 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I understand that AM radio is vertically polarised in the UK. A quarter wave dipole would be a bit unwieldy at those wavelengths, so loop antennas are used.

1. How long should the wire that is looped be?

1(a). Can connecting the AM aerial terminal to the central heating copper piping act as an aerial? I am discouraged from just trying this in case there's something I am not aware of which results in a release of the Magic Smoke.

2. How large should the loop be i.e. a diameter of about 20 cm seems common in those set-top AM aerials that come with stereo systems, but is there anything to be gained with a larger diameter loop?

3. I understand loops are directional, how should they be oriented? To roll towards the transmitter, or to roll at ninety degrees to the transmitter? (I am just curious about this because obviously the practical thing to do is just turn the loop for best reception.)

4. AM presumably could be used at higher frequencies, like FM broadcasts are in the UK. Would there be any practical advantages to this?

5. Can FM aerials be made into loops? Any practical benefits over a dipole other than size?

6. Ferrite rods: are they equivalent to magnifying lenses for light?

6(a). Could ferrite rod be used for FM to make a small aerial?

Thank you in advance for your patience in answering my questions. It is an ongoing point of interest with me, a tedious layman, although I struggle to understand bits and bobs at times (most times).

On 02/02/2022 16:05, David Paste wrote:

> Hello all,
>
> I return with yet more aerial related questions.
>
> The radio next to me has an AM radio with reception from 522 kHz to
1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I
understand that AM radio is vertically polarised in the UK. A quarter
wave dipole would be a bit unwieldy at those wavelengths, so loop
antennas are used.
Ah you're referring to MW (medium wave)

Before I answer the question of MW aerials, I didn't think there were
that many MW stations left on MW? In any case there would be DAB or FM
equivalents or even an internet radio station equivalent. The audio
quality will be better than on MW

if you're talking about DRM (Digital Radio Mondiale) then thats on the
SW Short wave bands
> 1. How long should the wire that is looped be?
>
> 1(a). Can connecting the AM aerial terminal to the central heating
copper piping act as an aerial? I am discouraged from just trying this
in case there's something I am not aware of which results in a release
of the Magic Smoke.
>
> 2. How large should the loop be i.e. a diameter of about 20 cm seems
common in those set-top AM aerials that come with stereo systems, but is
there anything to be gained with a larger diameter loop?
>
> 3. I understand loops are directional, how should they be oriented?
To roll towards the transmitter, or to roll at ninety degrees to the
transmitter? (I am just curious about this because obviously the
practical thing to do is just turn the loop for best reception.)
>
> 4. AM presumably could be used at higher frequencies, like FM
broadcasts are in the UK. Would there be any practical advantages to this?
>
> 5. Can FM aerials be made into loops? Any practical benefits over a
dipole other than size?
Yes they can. You often see this as a horizontal halo to recieve
stations from all directions but the gain is not as good as a vertical
dipole (Most FM stations use mixed polarity) Horizontal dipoles have
better gain than a halo but are obviously rather directional.

> 6. Ferrite rods: are they equivalent to magnifying lenses for light?

Not really, they alter the reactance of the coil and hence its
inductance. If my physics knowledge serves me right, an antenna based
on a ferrite rod is physically smaller than one designed in free air.
On some older radios there was often a knob to physically rotate the
ferrite antenna within the radio (to save you having to move the radio
itself)

> 6(a). Could ferrite rod be used for FM to make a small aerial?

the frequencies used for FM is 88 to 108 MHz so around 1000 times higher
than for the MW bands. The FM aerials are around 75 cm long and can pbe
pinned up on a house wall or put high up on a chimney stack if in a weak
reception area.

> Thank you in advance for your patience in answering my questions. It
is an ongoing point of interest with me, a tedious layman, although I
struggle to understand bits and bobs at times (most times).

On Wed, 2 Feb 2022 08:05:56 -0800 (PST), David Paste
<pastedavid@gmail.com> wrote:
>Hello all,
>
>I return with yet more aerial related questions.
>
>The radio next to me has an AM radio with reception from 522 kHz to 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I understand that AM radio is vertically polarised in the UK. A quarter wave dipole would be a bit unwieldy at those wavelengths, so loop antennas are used.
>
>1. How long should the wire that is looped be?
>
>1(a). Can connecting the AM aerial terminal to the central heating copper piping act as an aerial? I am discouraged from just trying this in case there's something I am not aware of which results in a release of the Magic Smoke.
>
>2. How large should the loop be i.e. a diameter of about 20 cm seems common in those set-top AM aerials that come with stereo systems, but is there anything to be gained with a larger diameter loop?
>
>3. I understand loops are directional, how should they be oriented? To roll towards the transmitter, or to roll at ninety degrees to the transmitter? (I am just curious about this because obviously the practical thing to do is just turn the loop for best reception.)
>
>4. AM presumably could be used at higher frequencies, like FM broadcasts are in the UK. Would there be any practical advantages to this?
>
>5. Can FM aerials be made into loops? Any practical benefits over a dipole other than size?
>
>6. Ferrite rods: are they equivalent to magnifying lenses for light?
>
>6(a). Could ferrite rod be used for FM to make a small aerial?
>
>Thank you in advance for your patience in answering my questions. It is an ongoing point of interest with me, a tedious layman, although I struggle to understand bits and bobs at times (most times).
How old is that radio? Surely it has an internal ferrite rod aerial
and you rotate the set to get best reception?
--
Dave W

On 02/02/2022 16:05, David Paste wrote:
> Hello all,
>
> I return with yet more aerial related questions.
>
> The radio next to me has an AM radio with reception from 522 kHz to 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I understand that AM radio is vertically polarised in the UK. A quarter wave dipole would be a bit unwieldy at those wavelengths, so loop antennas are used.
>
> 1. How long should the wire that is looped be?

Here's the one I built when I was a kid. Actually I built several.

http://www.iw5edi.com/ham-radio/3822/how-to-build-a-tuned-loop-antenna#:~:text=What%20is%20a%20Tuned%20Loop%20Antenna%3F%20The%20loop,to%201620%20khz%20section%20of%20the%20radio%20spectrum.

>
> 1(a). Can connecting the AM aerial terminal to the central heating copper piping act as an aerial?
Despite such things being earthed they often do work as an AM aerial.
When I was a teenage stop-go man (boy) I used to connect my tranny (shut
up) to the steel rail of the bridge if I happened to be on one. This
brought in Radio Caroline.

I am discouraged from just trying this in case there's something I am
not aware of which results in a release of the Magic Smoke.
Most unlikely, but get an unwanted child to make the connection while
you wait outside.
>
> 2. How large should the loop be i.e. a diameter of about 20 cm seems common in those set-top AM aerials that come with stereo systems, but is there anything to be gained with a larger diameter loop?

See the link above. I used to make them 40" per side.
>
> 3. I understand loops are directional, how should they be oriented? To roll towards the transmitter, or to roll at ninety degrees to the transmitter? (I am just curious about this because obviously the practical thing to do is just turn the loop for best reception.)
Endwise. Or align to null interference.

> 4. AM presumably could be used at higher frequencies, like FM broadcasts are in the UK. Would there be any practical advantages to this?
No.

>
> 5. Can FM aerials be made into loops?
Get the aluminium to about 450C and apply gentle pressure around a
former. Keep the heat away from the plastic junction box.

Any practical benefits over a dipole other than size?
No.

>
> 6. Ferrite rods: are they equivalent to magnifying lenses for light?
I can't make that analogy work.
>
> 6(a). Could ferrite rod be used for FM to make a small aerial?
Dunno

>
> Thank you in advance for your patience in answering my questions. It is an ongoing point of interest with me, a tedious layman, although I struggle to understand bits and bobs at times (most times).

It is my pleasure to serve.

Bill

On 02/02/2022 16:24, SH wrote:
> the frequencies used for FM is 88 to 108 MHz so around 1000 times higher
> than for the MW bands.

A hundred times.

Bill

On 02/02/2022 16:24, SH wrote:
> > 5. Can FM aerials be made into loops? Any practical benefits over a
> dipole other than size?
> Yes they can. You often see this as a horizontal halo to recieve
> stations from all directions but the gain is not as good as a vertical
> dipole (Most FM stations use mixed polarity) Horizontal dipoles have
> better gain than a halo but are obviously rather directional.

Halos are electrically long, but loops are electrically short. Also
halos are not closed loops. I believe it is possible to have VHF
aerials wound on ferromagnetic cores, with electrically short pieces of
wire, but it is normally better to have electrically long aerials, where
the size is manageable.

On 02/02/2022 16:05, David Paste wrote:
>
> 1. How long should the wire that is looped be?

Much shorter than a wavelength, but otherwise reasonably long but
subject to reasonable values of tuning capacitance.
>
> 1(a). Can connecting the AM aerial terminal to the central heating copper piping act as an aerial? I am discouraged from just trying this in case there's something I am not aware of which results in a release of the Magic Smoke.

Might well find that it is too close to your earth, so you end up with a
very narrow loop, which is not very good. If the smoke comes out, you
have serious problems with your earth bonding, and should be glad it
only came out of the radio, not your heart.

>
> 2. How large should the loop be i.e. a diameter of about 20 cm seems common in those set-top AM aerials that come with stereo systems, but is there anything to be gained with a larger diameter loop?

Within reason, a larger loop is better, subject to (1) above. However
the main design constraint is likely to be the size of the radio.

>
> 3. I understand loops are directional, how should they be oriented? To roll towards the transmitter, or to roll at ninety degrees to the transmitter? (I am just curious about this because obviously the practical thing to do is just turn the loop for best reception.)

To roll away from the transmitter, as the radiation pressure will tend
to push them in that direction :-).

>
> 4. AM presumably could be used at higher frequencies, like FM broadcasts are in the UK. Would there be any practical advantages to this?

If you are using it for communicating with aircraft, yes, because there
is no capture effect, so you can hear if a weaker station is trying to
use the same frequency and have some ability to work when another
aircraft has the microphone key stuck down. AM was used for mobile
radio, but narrow band FM, which uses a similar amount of spectrum
better tolerates electrical noise and co-channel interference.

>
> 5. Can FM aerials be made into loops? Any practical benefits over a dipole other than size?

FM is not a synonym for VHF. It can be used on medium wave frequencies,
although you would have to use narrowband FM to get a reasonable number
of stations.

Comments on electrically small VHF aerials in my other reply.

>
> 6. Ferrite rods: are they equivalent to magnifying lenses for light?

No. Lenses have to be electrically very large. They only start to
become practical at microwave frequencies, and there they will
dielectric, not magnetic field, devices, as is the case for optical lenses.

>
> 6(a). Could ferrite rod be used for FM to make a small aerial?

See my previous reply. You might not actually use ferrites, as they
might be rather lossy.
>
> Thank you in advance for your patience in answering my questions. It is an ongoing point of interest with me, a tedious layman, although I struggle to understand bits and bobs at times (most times).
>

On 2 Feb 2022 at 16:05:56 GMT, "David Paste" <pastedavid@gmail.com> wrote:

> 4. AM presumably could be used at higher frequencies, like FM broadcasts are
> in the UK. Would there be any practical advantages to this?

Airband uses 108MHz to 137Mhz with amplitude modulation. This is to mitigate
the capture effect that occurs with FM, so two AM transmissions on the same
frequency can still be heard. Safety first.
>
> 5. Can FM aerials be made into loops? Any practical benefits over a dipole
> other than size?
>
I have Wellbrook indoor loop (the one that looks like a blue hula-hoop).
Specifications suggest it can be used for FM broadcast reception although I've
never tried it.

--
Is something brilliant happening?

On Wed 02/02/2022 20:15, Dave W wrote:
> On Wed, 2 Feb 2022 08:05:56 -0800 (PST), David Paste
> <pastedavid@gmail.com> wrote:
>
>> Hello all,
>>
>> I return with yet more aerial related questions.
>>
>> The radio next to me has an AM radio with reception from 522 kHz to 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I understand that AM radio is vertically polarised in the UK. A quarter wave dipole would be a bit unwieldy at those wavelengths, so loop antennas are used.
>>
>> 1. How long should the wire that is looped be?
>>
>> 1(a). Can connecting the AM aerial terminal to the central heating copper piping act as an aerial? I am discouraged from just trying this in case there's something I am not aware of which results in a release of the Magic Smoke.
>>
>> 2. How large should the loop be i.e. a diameter of about 20 cm seems common in those set-top AM aerials that come with stereo systems, but is there anything to be gained with a larger diameter loop?
>>
>> 3. I understand loops are directional, how should they be oriented? To roll towards the transmitter, or to roll at ninety degrees to the transmitter? (I am just curious about this because obviously the practical thing to do is just turn the loop for best reception.)
>>
>> 4. AM presumably could be used at higher frequencies, like FM broadcasts are in the UK. Would there be any practical advantages to this?
>>
>> 5. Can FM aerials be made into loops? Any practical benefits over a dipole other than size?
>>
>> 6. Ferrite rods: are they equivalent to magnifying lenses for light?
>>
>> 6(a). Could ferrite rod be used for FM to make a small aerial?
>>
>> Thank you in advance for your patience in answering my questions. It is an ongoing point of interest with me, a tedious layman, although I struggle to understand bits and bobs at times (most times).
>
> How old is that radio? Surely it has an internal ferrite rod aerial
> and you rotate the set to get best reception?

A much easier solution: given that almost all VHF/FM transmissions are
now mixed polarisation, just put up a vertical dipole. It will get as
much signal as horizontal but - provided it is correctly mounted/sighted
- it will be true omni.
The only reason for horizontal antennae goes back to the early days when
transmitter powers were lower and above all receivers where nothing like
so sensitive as they are today. Ergo it was necessary to at least
attempt to reduce sensitivity to electrical interference which at least
in theory a horizontal aerial should achieve.

Somebody hear needs to read some books. You are comparing apples with
oranges in the original posts. If the mw set in question has an internal
ferrite rod you are stuffed in any case, Some have them on a hinge outside
and to some extent you can manipulate them. These are tuned circuits with
an inbuilt impedance match in the form of a coupling winding or a tap to the
coil. They replaced the old fashioned frame aerials which are now often used
by hobbyists as medium wave loops, but in this case the receiver needs to
not have a ferrite rod as it will much up the directivity of the frame or
loop.
Using AM at any frequency is still done. All the air band uses it just
above the FM frequencies. FM is used as it is only measuring the deviation
of the signal frequency so does not respond to am noise like clicks bangs
etc, but uses a lot more bandwidth for broadcast quality.

Aerials at vhf and uhf being a much higher frequency are directly tunable,
and hence resonant at one or a band of frequencies with some loss of signal
but still with a good directionality. In these cases you set for maximum
wanted signal but on am you tend to turn your loop which is bi directional
so you null out the interference if you can.
Polarisation on the MW is not so important though, as it gets messed up by
ionosphere reflection after dark when it goes further.

That is why its used of cours.
Quality is poor since channel spacing in most cases is 9Khz, and that is
thus the highest frequency you can hear.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"SH" <i.love@spam.com> wrote in message news:steb74$3bh$1@dont-email.me...
> On 02/02/2022 16:05, David Paste wrote:
>
> > Hello all,
> >
> > I return with yet more aerial related questions.
> >
> > The radio next to me has an AM radio with reception from 522 kHz to
> 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres. I
> understand that AM radio is vertically polarised in the UK. A quarter wave
> dipole would be a bit unwieldy at those wavelengths, so loop antennas are
> used.
> Ah you're referring to MW (medium wave)
>
> Before I answer the question of MW aerials, I didn't think there were that
> many MW stations left on MW? In any case there would be DAB or FM
> equivalents or even an internet radio station equivalent. The audio
> quality will be better than on MW
>
> if you're talking about DRM (Digital Radio Mondiale) then thats on the SW
> Short wave bands
> > 1. How long should the wire that is looped be?
> >
> > 1(a). Can connecting the AM aerial terminal to the central heating
> copper piping act as an aerial? I am discouraged from just trying this in
> case there's something I am not aware of which results in a release of the
> Magic Smoke.
> >
> > 2. How large should the loop be i.e. a diameter of about 20 cm seems
> common in those set-top AM aerials that come with stereo systems, but is
> there anything to be gained with a larger diameter loop?
> >
> > 3. I understand loops are directional, how should they be oriented?
> To roll towards the transmitter, or to roll at ninety degrees to the
> transmitter? (I am just curious about this because obviously the practical
> thing to do is just turn the loop for best reception.)
> >
> > 4. AM presumably could be used at higher frequencies, like FM
> broadcasts are in the UK. Would there be any practical advantages to this?
> >
> > 5. Can FM aerials be made into loops? Any practical benefits over a
> dipole other than size?
> Yes they can. You often see this as a horizontal halo to recieve stations
> from all directions but the gain is not as good as a vertical dipole (Most
> FM stations use mixed polarity) Horizontal dipoles have better gain than a
> halo but are obviously rather directional.
>
>
> > 6. Ferrite rods: are they equivalent to magnifying lenses for light?
>
> Not really, they alter the reactance of the coil and hence its inductance.
> If my physics knowledge serves me right, an antenna based on a ferrite rod
> is physically smaller than one designed in free air. On some older radios
> there was often a knob to physically rotate the ferrite antenna within the
> radio (to save you having to move the radio itself)
>
> > 6(a). Could ferrite rod be used for FM to make a small aerial?
>
> the frequencies used for FM is 88 to 108 MHz so around 1000 times higher
> than for the MW bands. The FM aerials are around 75 cm long and can pbe
> pinned up on a house wall or put high up on a chimney stack if in a weak
> reception area.
>
> > Thank you in advance for your patience in answering my questions. It
> is an ongoing point of interest with me, a tedious layman, although I
> struggle to understand bits and bobs at times (most times).

And very expensive as well. In that design of loop the high impedance can be
an issue when used to transmit as some seriously high voltages occur at the
ends where the tuning capacitor is added and hencye it has to be a vacuum
type, and I do have my doubts about how much you might be cooking your body
if you use it indoors!
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Ivan Plapp" <iplapp@channel7.television> wrote in message
news:stf1fh$62u$1@dont-email.me...
> On 2 Feb 2022 at 16:05:56 GMT, "David Paste" <pastedavid@gmail.com> wrote:
>
>> 4. AM presumably could be used at higher frequencies, like FM broadcasts
>> are
>> in the UK. Would there be any practical advantages to this?
>
> Airband uses 108MHz to 137Mhz with amplitude modulation. This is to
> mitigate
> the capture effect that occurs with FM, so two AM transmissions on the
> same
> frequency can still be heard. Safety first.
>>
>> 5. Can FM aerials be made into loops? Any practical benefits over a
>> dipole
>> other than size?
>>
> I have Wellbrook indoor loop (the one that looks like a blue hula-hoop).
> Specifications suggest it can be used for FM broadcast reception although
> I've
> never tried it.
>
>
> --
> Is something brilliant happening?

On 03/02/2022 08:34, Brian Gaff (Sofa) wrote:
> Polarisation on the MW is not so important though, as it gets messed up by
> ionosphere reflection after dark when it goes further.
>

Actually, I thought ground wave propagation, which is what is relied on
within the primary service area, requires vertical polarisation.

In article <steb74$3bh$1@dont-email.me>,
SH <i.love@spam.com> wrote:

> > 6. Ferrite rods: are they equivalent to magnifying lenses for light?

> Not really, they alter the reactance of the coil and hence its
> inductance. If my physics knowledge serves me right, an antenna based
> on a ferrite rod is physically smaller than one designed in free air.
> On some older radios there was often a knob to physically rotate the
> ferrite antenna within the radio (to save you having to move the radio
> itself)

The ferrite rod can be viewed almost like a 'grip' that has taken hold of
of the radio broadcast's RF magnetic field over a large volume and pulled
it togther to pass along the rod, though the coil. I looks like this if you
plot the external field lines.

Thus is 'pulls in more signal power'. (In standard antenna terms it has a
wider 'effective area'.)

The higher the mu value, the bigger the effect. Alas, this also tends to go
with the response being 'slower'. So the effect tends not to work at much
higher frequencies. Thus although you can use a ferrite rod at, say, 100
MHz, it's ability to 'pull in' signal power is much less than in the MW/LW
bands. So not usually used above MW for domestic reception.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

Well if that is so, why is it that certain stations which use a horizontal
aerial between two chimneys still go quiet if you stand a portable radio on
its end so the ferrite is vertical?
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"David Woolley" <david@ex.djwhome.demon.invalid> wrote in message
news:stgalp$s87$1@dont-email.me...
> On 03/02/2022 08:34, Brian Gaff (Sofa) wrote:
>> Polarisation on the MW is not so important though, as it gets messed up
>> by
>> ionosphere reflection after dark when it goes further.
>>
>
> Actually, I thought ground wave propagation, which is what is relied on
> within the primary service area, requires vertical polarisation.

"Brian Gaff \(Sofa\)" <briang1@blueyonder.co.uk> wrote:
> Well if that is so, why is it that certain stations which use a horizontal
> aerial between two chimneys still go quiet if you stand a portable radio on
> its end so the ferrite is vertical?

Ferrite rods give most signal when they're at right angles to the
transmitter polarisation - I think.

--
Chris Green
·

On 04/02/2022 11:06, Brian Gaff (Sofa) wrote:
> Well if that is so, why is it that certain stations which use a horizontal
> aerial between two chimneys still go quiet if you stand a portable radio on
> its end so the ferrite is vertical?

That behaviour of the ferrite aerial confirms that the polarisation is
vertical.

I imagine the horizontal part of the transmitting aerial is providing a
capacitive hat, and the actively radiating part is what you are assuming
is a feeder cable.

<https://en.wikipedia.org/wiki/T-antenna>

On 04/02/2022 11:21, Chris Green wrote:
> Ferrite rods give most signal when they're at right angles to the
> transmitter polarisation - I think.

That's true, because polarisation is defined as being the E field
polarisation.

On 16:05 2 Feb 2022, David Paste said:

> Hello all,
>
> I return with yet more aerial related questions.
>
> The radio next to me has an AM radio with reception from 522 kHz to
> 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres.
> I understand that AM radio is vertically polarised in the UK. A
> quarter wave dipole would be a bit unwieldy at those wavelengths, so
> loop antennas are used.
>
> 1. How long should the wire that is looped be?
>
> 1(a). Can connecting the AM aerial terminal to the central heating
> copper piping act as an aerial? I am discouraged from just trying
> this in case there's something I am not aware of which results in a
> release of the Magic Smoke.

I have a 1940s valve radio which needs an external aerial like yours. I
haven't used it in ages but we would use a long wire. Positioning a
loop every time you tune a station would be too fiddly. Using an earth
would be posh.

The last time I tried it the creaky old thing was working well. It's
almost identical to this one on eBay, although not as glossy and
perfect. Mine has a wooden case and I love it to bits. Visitors think
it's some broken old radio kept as an ornament but actually it's kept
because it works.

https://www.ebay.co.uk/itm/224819633440

In message <XnsAE35FBC3B84937B93@144.76.35.252>, Pamela
<pamela.private.mailbox@gmail.com> writes
>On 16:05 2 Feb 2022, David Paste said:
>
>> Hello all,
>>
>> I return with yet more aerial related questions.
>>
>> The radio next to me has an AM radio with reception from 522 kHz to
>> 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres.
>> I understand that AM radio is vertically polarised in the UK. A
>> quarter wave dipole would be a bit unwieldy at those wavelengths, so
>> loop antennas are used.
>>
>> 1. How long should the wire that is looped be?
>>
>> 1(a). Can connecting the AM aerial terminal to the central heating
>> copper piping act as an aerial? I am discouraged from just trying
>> this in case there's something I am not aware of which results in a
>> release of the Magic Smoke.
>
>I have a 1940s valve radio which needs an external aerial like yours. I
>haven't used it in ages but we would use a long wire. Positioning a
>loop every time you tune a station would be too fiddly. Using an earth
>would be posh.
>
>The last time I tried it the creaky old thing was working well. It's
>almost identical to this one on eBay, although not as glossy and
>perfect. Mine has a wooden case and I love it to bits. Visitors think
>it's some broken old radio kept as an ornament but actually it's kept
>because it works.
>
>https://www.ebay.co.uk/itm/224819633440

Before ferrite rods, some radios did have internal loop aerials inside
the wooden case (usually with additional connections for an external
aerial and earth). Obviously the loop was directional, but unless the
required station was exactly in one of the two broadside nulls, the
orientation of the radio was probably not that critical for normal
domestic use.

Regarding using old radios and record players, I'm rather bemused when
someone brings one into The Repair Shop (on TV) for restoration. So far
I've never seen any repairer take the precaution of at least doing a
slow, controlled wind-up of the mains voltage to give the electrolytic
capacitors a chance to reform, and to minimise the chances of other
catastrophic failures.
--
Ian

On Sat 05/02/2022 08:48, Ian Jackson wrote:
> In message <XnsAE35FBC3B84937B93@144.76.35.252>, Pamela
> <pamela.private.mailbox@gmail.com> writes
>> On 16:05  2 Feb 2022, David Paste said:
>>
>>> Hello all,
>>>
>>> I return with yet more aerial related questions.
>>>
>>> The radio next to me has an AM radio with reception from 522 kHz to
>>> 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres.
>>> I understand that AM radio is vertically polarised in the UK. A
>>> quarter wave dipole would be a bit unwieldy at those wavelengths, so
>>> loop antennas are used.
>>>
>>> 1. How long should the wire that is looped be?
>>>
>>> 1(a). Can connecting the AM aerial terminal to the central heating
>>> copper piping act as an aerial? I am discouraged from just trying
>>> this in case there's something I am not aware of which results in a
>>> release of the Magic Smoke.
>>
>> I have a 1940s valve radio which needs an external aerial like yours. I
>> haven't used it in ages but we would use a long wire. Positioning a
>> loop every time you tune a station would be too fiddly. Using an earth
>> would be posh.
>>
>> The last time I tried it the creaky old thing was working well. It's
>> almost identical to this one on eBay, although not as glossy and
>> perfect.  Mine has a wooden case and I love it to bits.  Visitors think
>> it's some broken old radio kept as an ornament but actually it's kept
>> because it works.
>>
>> https://www.ebay.co.uk/itm/224819633440
>
> Before ferrite rods, some radios did have internal loop aerials inside
> the wooden case (usually with additional connections for an external
> aerial and earth). Obviously the loop was directional, but unless the
> required station was exactly in one of the two broadside nulls, the
> orientation of the radio was probably not that critical for normal
> domestic use.
>
[snip]

It was years before I understood why my parents had their Busch AC11
(which I still have in the loft) on a wheeled trolley so it could be
moved around.

On 05/02/2022 01:32, Pamela wrote:
> On 16:05 2 Feb 2022, David Paste said:
>
>> Hello all,
>>
>> I return with yet more aerial related questions.
>>
>> The radio next to me has an AM radio with reception from 522 kHz to
>> 1629 kHz, giving approximate wavelengths of 574 metres to 184 metres.
>> I understand that AM radio is vertically polarised in the UK. A
>> quarter wave dipole would be a bit unwieldy at those wavelengths, so
>> loop antennas are used.
>>
>> 1. How long should the wire that is looped be?
>>
>> 1(a). Can connecting the AM aerial terminal to the central heating
>> copper piping act as an aerial? I am discouraged from just trying
>> this in case there's something I am not aware of which results in a
>> release of the Magic Smoke.
>
> I have a 1940s valve radio which needs an external aerial like yours. I
> haven't used it in ages but we would use a long wire. Positioning a
> loop every time you tune a station would be too fiddly. Using an earth
> would be posh.
>
> The last time I tried it the creaky old thing was working well. It's
> almost identical to this one on eBay, although not as glossy and
> perfect. Mine has a wooden case and I love it to bits. Visitors think
> it's some broken old radio kept as an ornament but actually it's kept
> because it works.
>
> https://www.ebay.co.uk/itm/224819633440

When I was a kid, mid seventies, I had a "Six Million Dollar Man" doll
in my toy box, an Action Man kind of thing. It had an accessory backpack
AM radio, which was a Crystal Set design with a long trailing wire for
an aerial. Would have been worth something on eBay now.

Anyway, we had a BT rotary dial-stop telephone back then, and I somehow
found connecting the aerial wire to the dial-stop made a massive
improvement to its pickup of broadcasts.

Must have been the very long telephone wires strung down the street.

Strangely, I don't remember it needing an earth connection.

--
Adrian C

On 05.02.2022 02:32, Pamela wrote:
>
> I have a 1940s valve radio which needs an external aerial like yours. I
> haven't used it in ages but we would use a long wire. Positioning a
> loop every time you tune a station would be too fiddly. Using an earth
> would be posh.
>
> The last time I tried it the creaky old thing was working well. It's
> almost identical to this one on eBay, although not as glossy and
> perfect. Mine has a wooden case and I love it to bits. Visitors think
> it's some broken old radio kept as an ornament but actually it's kept
> because it works.
>
> https://www.ebay.co.uk/itm/224819633440

Hii Pamela,

you are probably aware, but just in case.

If the radio hasn't been properly restored there is a danger of serious
damage to components which are no longer available (mains and output
transformers) if switched on after a long period of storage. Some
coupling Capacitors are notorious for becoming leaky, leading to
overstressed output valves and high currents causing damage to these
components.

Sorry if I'm teaching my grandmother to suck eggs but I though it a good
idea to mention this to possibly prevent a much loved radio being damaged.

In article <stev3l$n2t$1@dont-email.me>, David Woolley
<david@ex.djwhome.demon.invalid> wrote:
> Halos are electrically long, but loops are electrically short. Also
> halos are not closed loops. I believe it is possible to have VHF
> aerials wound on ferromagnetic cores, with electrically short pieces of
> wire, but it is normally better to have electrically long aerials, where
> the size is manageable.

Yes. At VHF the mu values tend to be lower, so less 'gain'. And the ferrite
is easily saturated, so more impulse noise, etc. So in general a whip or
dipole make more sense at VHF.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 10:27 5 Feb 2022, Eddie King said:

> On 05.02.2022 02:32, Pamela wrote:
>>
>> I have a 1940s valve radio which needs an external aerial like
>> yours. I haven't used it in ages but we would use a long wire.
>> Positioning a loop every time you tune a station would be too
>> fiddly. Using an earth would be posh.
>>
>> The last time I tried it the creaky old thing was working well. It's
>> almost identical to this one on eBay, although not as glossy and
>> perfect. Mine has a wooden case and I love it to bits. Visitors
>> think it's some broken old radio kept as an ornament but actually
>> it's kept because it works.
>>
>> https://www.ebay.co.uk/itm/224819633440
>
> Hii Pamela,
>
> you are probably aware, but just in case.
>
> If the radio hasn't been properly restored there is a danger of
> serious damage to components which are no longer available (mains and
> output transformers) if switched on after a long period of storage.
> Some coupling Capacitors are notorious for becoming leaky, leading to
> overstressed output valves and high currents causing damage to these
> components.
>
> Sorry if I'm teaching my grandmother to suck eggs but I though it a
> good idea to mention this to possibly prevent a much loved radio
> being damaged.

It's new to me and Ian mentioned something about caapcitors. It's probably
5 years since I used the radio. What drill should I follow next time I use
it?

On 08:48 5 Feb 2022, Ian Jackson said:

> In message <XnsAE35FBC3B84937B93@144.76.35.252>, Pamela
> <pamela.private.mailbox@gmail.com> writes
>>On 16:05 2 Feb 2022, David Paste said:
>>
>>> Hello all,
>>>
>>> I return with yet more aerial related questions.
>>>
>>> The radio next to me has an AM radio with reception from 522 kHz to
>>> 1629 kHz, giving approximate wavelengths of 574 metres to 184
>>> metres. I understand that AM radio is vertically polarised in the
>>> UK. A quarter wave dipole would be a bit unwieldy at those
>>> wavelengths, so loop antennas are used.
>>>
>>> 1. How long should the wire that is looped be?
>>>
>>> 1(a). Can connecting the AM aerial terminal to the central heating
>>> copper piping act as an aerial? I am discouraged from just trying
>>> this in case there's something I am not aware of which results in a
>>> release of the Magic Smoke.
>>
>>I have a 1940s valve radio which needs an external aerial like yours.
>>I haven't used it in ages but we would use a long wire. Positioning a
>>loop every time you tune a station would be too fiddly. Using an
>>earth would be posh.
>>
>>The last time I tried it the creaky old thing was working well. It's
>>almost identical to this one on eBay, although not as glossy and
>>perfect. Mine has a wooden case and I love it to bits. Visitors
>>think it's some broken old radio kept as an ornament but actually
>>it's kept because it works.
>>
>>https://www.ebay.co.uk/itm/224819633440
>
> Before ferrite rods, some radios did have internal loop aerials
> inside the wooden case (usually with additional connections for an
> external aerial and earth). Obviously the loop was directional, but
> unless the required station was exactly in one of the two broadside
> nulls, the orientation of the radio was probably not that critical
> for normal domestic use.
>
> Regarding using old radios and record players, I'm rather bemused
> when someone brings one into The Repair Shop (on TV) for restoration.
> So far I've never seen any repairer take the precaution of at least
> doing a slow, controlled wind-up of the mains voltage to give the
> electrolytic capacitors a chance to reform, and to minimise the
> chances of other catastrophic failures.

I haven't used the radio for about 5 years, when it worked fine. What
precautions should I follow to keep it going?

I've never heard of reforming capacitors. How do you do a "slow,
controlled wind-up of the mains voltage" or anything else that's needed? I
couldn't find any decent web pages offering advice.

I was given the radio second-hand by the local TV shop which was throwing
it out 50 years ago and it would be nice to keep it going.

All the components are original (I once changed the speaker cloth!) but I
don't have the stamina or equipment to get into a restoration project
swapping lots of new components for old. However if doing something pays
dividends then I would have to do it.