The AM Forum

Hi

I have a Yaesu FT1000MP, this radio has the most modifiable service menu ever made. My question ...  is there any advantage to running AM with one sideband ?? I can configure the menu in the AM mode to strip off whatever sideband I want.  I know the transmitter frequency response with be twice as wide using the 6 khz AM filter basically about 50hz to 6khz by shifting the IF ( Carrier Point ) over to the filters edge. So if I run it with carrier plus lower sideband what can I expect ?? Will there be an advantage in more power output both in the radio and linear ??

Any downside to doing this ??

Interesting question. My old Drake TR-3 transceiver can be used on AM and it puts out a SSB signal along with the carrier. My old Swan 500 and Swan SW-240 does this also. I guess it would not be real HI-FI type audio, but people can hear it OK on the receiving end.  73s,  Marty, KK4RF

The downside to carrier & one sideband is distortion when demodulated with a diode-type detector which is common in older receivers.  However, a synchronous-type detector cleans everything up.  See pix below.

Here's a chance for me to learn something new. I'm surprised to see those scope shots: IIRC, the Collins KWS-1 uses carrier with one sideband for AM, and given that company's reputation for higher-than-usual audio quality, I'm curious what percentage of THD the diode detector introduces, and if the 75A-4 receiver uses a diode detector for AM.

Thanks!

73,

Bill, W4EWH

My National NCX-3 runs SSB carrier inserted and I use it on AM.  I receive good audio reports and some AMers are surprised when I tell them I am running pretend AM. 

Chris, N4JOY 

That's why you should try to get an audio report before you tell the other guy what you're running. Had similar experiences with my KWS-1 and TR-7 transmitters.

Yes distortion is increased somewhat in a conventional detector with SSB AM full carrier, but all of the information is there.

The broadcasters toyed with reduced carrier SSB (about 6db down carrier level) and the use of Synchronous detectors as a way to reduce bandwidth and increase the dismal efficiency of AM at least up to around 60% instead of the theoretical 33% on conventional AM.

SSB (H3E , R3E) signals can be demodulated with a product or synchronous detector. SSB H3E (-6 dB) allows for envelope detection. The audio quality is poor however.

https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BS.1059-1-1990-PDF-E.pdf

IF (that's the "big IF") when you shift to one side band you actually get a response out to 6kHz audio,
and it is not cutoff by internal audio level or RF level filtering, then imho, yes it would be a big advantage when
communicating with AM ops using a wider than the nominal 3.1kHz SSB passband typical of most tranceivers
and the like.

Most receivers will not know you are missing one sideband at all.