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I have tried programming approach frequencies into my baofeng and cannot hear any transmissions. Freq programming was done using a desktop computer connected to the radio to frequency 121.9MHZ. Nothing was heard, just standard background static. Here is the radio: https://www.amazon.com/Baofeng-Warranty-Dual-Band-Radio-Improved/dp/B00HX03AMA Baofeng UV5R v2

Marcus Müller
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jason97m
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    There's no such thing as "standard baofeng". You'll need to specify which model you use. – Marcus Müller Dec 31 '16 at 15:08
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    Also, the person best able to answer your question is you: look at the specs of your device, and find out whether it covers the frequencies you're interested in. – Marcus Müller Dec 31 '16 at 15:09
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    Also, you don't specify what you're trying to demodulate. Also, again, there's no such thing as standard background noise. – Marcus Müller Dec 31 '16 at 15:10
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    So @Marcus, you are getting too far in the weeds, and as I am new I don't just "know" what to look for or specify. The model is there, but it is not pertinent as I am wondering if the frequency is somehow coded or modulated in a way that a BAOFENG UV-5R is not designed to receive due to regulations against just anyone being able to receive the transmissions. – jason97m Dec 31 '16 at 16:06
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    And I would say there is standard background static, as in nothing out of the ordinary was heard such as odd pulsing or even silence indicating the radio does not work. Feel free to vote me down more, but the question is fair. – jason97m Dec 31 '16 at 16:08
  • first of all, great that you've edited your question a couple of minutes ago and added the radio type! So, to what kind of modulation did you program your UV5R to? – Marcus Müller Dec 31 '16 at 16:27
  • (and noise is not always the same – I could go on for hours about the mathematical/physical properties of different kinds of noises, but that really doesn't help here) – Marcus Müller Dec 31 '16 at 16:27
  • I entered 119.3, our local tower into my radio, but it said 'Cancel' at the last digit, even though I was on VHF. – HeavenlyHarmony Oct 27 '19 at 21:02

5 Answers5

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As far as I've read, all Baofeng radios do FM only. The majority of aircraft communications uses AM, so whether or not it can be tuned there, you would not hear the audio, just approximate silence (quieter the stronger the signal).

This is because to a FM receiver's perspective, an AM signal is unmodulated (the frequency stays constant), and vice versa (in a FM signal the amplitude stays constant).

In some cases, the speech may be very faintly audible, due to imperfect circuits in both the transmitter (causing frequency variation in the transmitted signal) and the receiver (having unintended sensitivity to amplitude variations).

In the reverse case — attempting to receive a FM signal using an AM receiver — this can actually be used practically (improvised “slope detection”, tuning with an offset and allowing the frequency modulated signal to be converted by the edge of the receiver's filter to an amplitude-and-frequency modulate signal).

Kevin Reid AG6YO
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    Thanks, that about sums up what I was trying to find out....most airband is on AM versus FM. – jason97m Jan 01 '17 at 18:45
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    You got it. FM receivers are funny, though. If the signal is below the threshold of the limiter you can sometimes hear it. To try this out, set it to WFM and maybe try smaller antennas to see if you can hear anything. Those radios are a great deal for the price. Lots of fun. Just be careful to NEVER transmit in that band. – SDsolar Jan 02 '17 at 17:45
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From the amazon page you've linked to:

Frequency Range: 136-174 / 400-479.995 MHz.

So, no, you can't receive 121.9 MHz.

Marcus Müller
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    Looks like the software change on the radio only allows for display of the frequency. However, my question wasn't really about the frequency ranges, but was about whether the radio had the physical capability to accomplish this....such as filters would still allow other frequencies through. – jason97m Jan 01 '17 at 18:42
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    "not about frequency ranges, but about physical capability": supported frequencies is the most fundamental physical capability of any radio. – Marcus Müller Jan 01 '17 at 18:46
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    Maybe the most fundamental, but not what he was looking for. My biggest concern about physical capability is the chance of actually transmitting in that band. The way they are coming down on people with laser pointers, just imagine how they would react to interference to their communications. No thank you very much. – SDsolar Jan 02 '17 at 17:50
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    I worry less about someone facing legal enforcement over abusing that part of the spectrum than I worry about that spectrum being accidentally abused by Op - to be completely frank, he doesn't seem to be the most competent – Marcus Müller Jan 02 '17 at 19:09
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It is far from being ideal, but it is possible. UV-5R can get below the specified range (google Chirp) and although it is an FM radio, it can (under some conditions) receive an AM modulated audio signal. The quality is bad, but if the signal is strong, it is audible. I've tested this on ATIS from a nearby airport (~131 MHz). What also helps is to set WFM and tune slightly off the carrier frequency (in my case 6 kHz up was the sweet spot). Seems to be working approx. down to 126 MHz. Although the frequency can be set even lower, it doesn't seem to receive anything (tried with TinySA).

!Never ever transmit on that band (rather even disable the TX capability in VHF band in the SW)!

MPf
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I believe the tower & aircraft are on digital, not analogue systems. Though i think it's possible to receive transmissions from ground crew (fuel tankers, gangway vehicle & other airside staff), who communicate on certain analogue frequencies. Tugs, baggage train's etc. Haven't done this myself but have been told it is possible to receive them in the UK.

Snowy
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Yes, it can receive air band transmissions but upper the frequency limit is 127 MHz or 128 MHz. I can get the airport but the speech very faintly audible. This is because from an FM receiver perspective, an AM signal is unmodulated.

Anyway, I can receive AM signals with a Baofeng UV5R but the sound is awful.

Kevin Reid AG6YO
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Kourosh Delpak
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