Above 108MHz with FM radio?
Kunyavsky
Hi
I was wondering if it is possible to modify a regular FM radio
(not with digital tuner) so it would pick up frequencies above 108MHz.
108 to 130something is the aircraft comunication band, I am just
curious to listen in. I am pretty sure there is nothing illigal
about that.
I was thinking about soldering a capacitor in series with the variable
tuning capacitor. Would that work?
Is there some other easy fix?
Thanks
Gregory Kunyavsky
gr...@ica.net
larry
As a matter of information, the aircraft band uses AM modulation.
Also fm broadcasting is done using very wide band fm, in the
neighbourhood of 100 to 200 khz bandwidth, whereas the typical fm
radio is around 5 khz bandwidth.
Larry ve3fxq
Mark Kinsler
Kunyavsky <gr...@ica.net> wrote:
>I was wondering if it is possible to modify a regular FM radio
>(not with digital tuner) so it would pick up frequencies above 108MHz.
>108 to 130something is the aircraft comunication band, I am just
>curious to listen in. I am pretty sure there is nothing illigal
>about that.
>
> I was thinking about soldering a capacitor in series with the variable
>tuning capacitor. Would that work?
>Is there some other easy fix?
I don't know how much increase you'd get, but you might try simply
adjusting the oscillator trimmer capacitor and/or coils. Be gentle.
Once you get to the proper frequency range, re-adjust the pre-selector
and rf amplifier trimmer.
It's certainly not illegal. Radio Shack sells such receivers. Expect
to hear a lot of nothing, because these frequencies are shared, and
they're off the air unless somebody has something to say. And even then
they're very brief about it.
Mark Kinsler
Mark Zenier
: I was wondering if it is possible to modify a regular FM radio
: (not with digital tuner) so it would pick up frequencies above 108MHz.
: 108 to 130something is the aircraft comunication band, I am just
: curious to listen in. I am pretty sure there is nothing illigal
: about that.
: I was thinking about soldering a capacitor in series with the variable
: tuning capacitor. Would that work?
: Is there some other easy fix?
If you can still find one with a dial. ;-) But the bad news is
that aircraft use AM, so that part doesn't work too well.
Just adjusting the coils will work. Either spreading them or rewinding
them with a few less turns. I managed to get a good FM tuner up to
cover the 2 meter ham band and pick up the local repeaters. The goal
was to get the 137 MHz weather satellites, but I decided that I'd rather
have a good FM DX receiver (my local reception is lousy) so I could get
the broadcasts from the next city north, so I tuned it back.
Mark Zenier mze...@eskimo.com mze...@netcom.com
David Jenkins
Mark Kinsler wrote:
>
> Kunyavsky <gr...@ica.net> wrote:
> >I was wondering if it is possible to modify a regular FM radio
> >(not with digital tuner) so it would pick up frequencies above 108MHz.
> >108 to 130something is the aircraft comunication band, I am just
> >curious to listen in. I am pretty sure there is nothing illigal
> >about that.
> >
> > I was thinking about soldering a capacitor in series with the variable
> >tuning capacitor. Would that work?
> >Is there some other easy fix?
>
> adjusting the oscillator trimmer capacitor and/or coils. Be gentle.
> Once you get to the proper frequency range, re-adjust the pre-selector
> and rf amplifier trimmer.
> It's certainly not illegal. Radio Shack sells such receivers. Expect
> to hear a lot of nothing, because these frequencies are shared, and
> they're off the air unless somebody has something to say. And even then
> they're very brief about it.
>
> Mark Kinsler
don't mess up your FM radio. The aircraft band is AM and Radio Shack
sells the Aircraft Band radios at very reasonable prices including a no
solder kit.
GMoon21870
You can slide a manual tuning radio's coverage. There should be a small
box about 1 1/2" sq X 1/4" deep, usually clear plastic. On the top of this
box there will be either 2 to 4 small slotted screws. One of these will
adjust the coverage. Make sure you do this on a radio you can afford to
throw away in case it get screwed up and note the orignal position of the
screw.
Michael Black
The problem with this is that the FM broadcast band uses FM and is quite
wideband, while the aircraft band just above it uses AM and is relatively
narrow band. If the FM receiver is a lousy design, it might detect some
AM signals. But most of the FM BCB receivers I'm seeing these days use
IC's so they probably are pretty good FM receivers, and even if not there
is still the wide bandwidth problem.
As for retuning, it can be done. BUt it would be more of a case of
reducing the number of turns of wire in the coils in the front end,
or reducing the total capacitance across those same coils. Often,
there are trimmers that might possibly have enough range to move
the tuning range up enough. Or there are fixed capacitors in parallel
with the coils and variable tuning capacitor and reducing their value
or eliminating them might get the tuning range moved up enough.
If you put fixed capacitors in series with the variable capacitor
(actually, the variable capacitor will have two or more sections, one
for the local oscillator, and one or more for the tuned circuits at
the incoming signal frequency), it will reduce the tuning range, but
not move it.
Ramsey Electronics used to have, and probably still has, a kit for
building an aircraft band receiver.
A traditional method of receiving the aircraft band without building
or buying a whole receiver is a converter, ie a mixer/oscillator (and
maybe an rf amplifier), which translates the aircraft band down to
an AM receiver at a lower frequency. A car radio makes a good
radio for this, since it does not have a loopstick and the dial is
fairly good. Problem is that it only tunes a 1 MHz range, and the
aircraft band is twenty MHz or so. Using a tuneable oscillator in
the converter overcomes this, though then you have to figure out a dial
scheme for it, and it will drift.
Michael
On Fri, 21 Mar 1997, Kunyavsky wrote:
> Hi
>
> I was wondering if it is possible to modify a regular FM radio
> (not with digital tuner) so it would pick up frequencies above 108MHz.
> 108 to 130something is the aircraft comunication band, I am just
> curious to listen in. I am pretty sure there is nothing illigal
> about that.
>
> I was thinking about soldering a capacitor in series with the variable
> tuning capacitor. Would that work?
> Is there some other easy fix?
>
> Thanks
>
> Gregory Kunyavsky
> gr...@ica.net
>
>
Mark Coniglio
> On Fri, 21 Mar 1997, Kunyavsky wrote:
>
> > Hi
> >
> > I was wondering if it is possible to modify a regular FM radio
> > (not with digital tuner) so it would pick up frequencies above 108MHz.
> > 108 to 130something is the aircraft comunication band, I am just
> > curious to listen in. I am pretty sure there is nothing illigal
> > about that.
> >
> > I was thinking about soldering a capacitor in series with the variable
> > tuning capacitor. Would that work?
> > Is there some other easy fix?
> >
> > Thanks
> >
> > Gregory Kunyavsky
> > gr...@ica.net
I am pretty sure that JDR sells an Aircraft Band tuner for $30 or so. Try
going to www.jdr.com and checking out their kits.
-- Mark Coniglio
--
mail: tro...@panix.com
web: http://www.art.net/~troika
Henry A. Kolesnik
Lower the cap might work but I doubtt it would allow the radio to tune
high enough. best bet is to remove some turns from coils, rf and osc.
I think you interest in aircraft and I beleive they use am.
Efrein Gago Cerezal
On Fri, 21 Mar 1997, Kunyavsky wrote:
> Hi
>
> I was wondering if it is possible to modify a regular FM radio
> (not with digital tuner) so it would pick up frequencies above 108MHz.
Yes, by tuning to higher capacity the local oscillator trimmer, and
then retuning the rf input filter trimmer (both in the main variable
capacitor of the receiver)
BUT
aircraft communication is plain AM -not FM- and you won't be able
to listen to it in an FM receiver (unless it has a pretty high spurious AM
demodulation). What you could do is to inject the 10.7 MHz IF signal into
a cheap shortwave receiver.
OR EVEN BETTER
Forget the radio receivers and use a VHF TV tuner, as those built inside
almost any Video Recorder. The tuner has to cover the air band. European
tuners already do, since this band is also allocated for cable-TV in some
countries.
A TV tuner has a high-quality AM demodulator for the video signal, and
the only thing you have to do is to tune into the right frequency. You can
extract the demodulated audio from the Baseband Video Output connector.
The output signal has to be boosted by an audio amplifier before applying
to a loudspeaker or to headphones (b careful!)
I think it is better to try such a cheap arrange before spending
money in a receiver. You'll perhaps become fed up of hearing to pilots
after a couple of days!
saludos
Efrein Gago
efr...@cryogen.com
Michael Black
The idea of feeding the 10.7MHz IF singal into a shortwave receiver is
a good one, a neat trick that you'd see mentioned in the amateur
radio magazines years ago. The narrow bandwidth of the shortwave
receiver might be a problem, because FM broadcast receivers are not
high stability units.
The video recorder idea is an even neater trick. One thing to remember,
though, is that the audio subcarrier is not always AM. It depends on
the country and their tv standard. Here in North America, the audio
subcarrier is FM, which would be the same problem as with the FM
broadcast receiver.
Michael
Efrein Gago Cerezal
Michael Black <blac...@CAM.ORG> dijo:
> One thing to remember,
> though, is that the audio subcarrier is not always AM. It depends on
> the country and their tv standard. Here in North America, the audio
> subcarrier is FM, which would be the same problem as with the FM
> broadcast receiver.
I am sorry because I had to explain better. What I was suggesting
to do is to demodulate the AM audio signal by using the AM video
demodulator of the receiver.
This simple solution is to process the narrowband AM signal
the same way the receiver does with the wide-band video signal.
As an exception, people having a French TV receiver probably would
find more convenient to use the audio demodulator, since audio in the
French system is AM (as far as I remember)
Anyway, I think that the audio demodulator of a number of video recorders
latches to the audio signal only if the video carrier is found in the
expected frequency. This circumstance could turn reception a bit
difficult.
--
Efrein Gago