> I seem to remember that the aircraft radios we used during the 60-80s > in P-3s/C-130s etc (ARC-94/102 aka 618T) had a selection called AME > (AM equivalent). It was explained to us (pilots) by the techs that it
> wasn't a high level AM, but USB with carrier. It sounded OK, but then > again, it was designed for communications and not "easy listening"! > All the airways communication now days is SSB, so the AME position > rarely gets selected. > > Perhaps someone is familiar with that mode and can expand on it. > > 73 Tom/W4OKW ------------------------------ >>Aircraft VHF radios still use full carrier AM. I have a small Radio Shack portable with the aircraft band, and there is >>a lot of AM traffic on it. I purchased it mainly to use as a tool for sniffing out power line noise. The reason they use >>AM instead of FM is the capture effect of FM. With AM, when a strong signal is on frequency, a weaker one can still be >>heard under the stronger one. It would be a catastrophe waiting to happen if aircraft used FM radios and a stronger >>signal completely overrode, particularly near a busy airport. Also, I seem to recall something about SSB being less >>than satisfactory due to the shift in frequency due to the Doppler effect, with high speed jet aircraft. >>Don k4kyv ------------Tom sez------------------------------------------ Hi Don, It probably would have been helpful if I had prefaced my comments with "HF Airways (long range over water) comms"!! I suspect that the Doppler effect on HF is minimal or SSB wouldn't be universal for HF air to ground today. Back in the day, 6567 KHz was a nearly universal AM frequency shared by Miami, New York and San Juan radio. I don't see any AM frequencies listed in the DOD In-flight Handbook or the ARINC listings. The weather broadcasts like 10051.0 (New York, Gander, Shanwick) are sideband too. I have looked inside several Collins VHF xcvrs (although not the newer Pro-Line stuff) and sure enough they used high level Plate (collector!) modulated AM. I imagine the newer ones use "computer generated" AM or some such magic!. We (pilots, military and commercial) were taught that FM was not used, as you say, due to the capture effect. With AM when someone "doubles", it is pretty obvious. Safety of flight issue. 73 de Tom/W4OKW ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
