HFU HF Underground

General Category => Amateur Radio => Topic started by: ThaDood on March 21, 2022, 0419 UTC

Title: USB trend noticed on both 75M and 40M? As well as C4FM.
Post by: ThaDood on March 21, 2022, 0419 UTC

Has anyone else noticed this on both the 75M and 40M bands the last few months? I've been noticing USB being used more on these bands,  instead of LSB, mode. Now, as far as I know, there's nothing in the rules that says that an op can't do that, but even tonight, on 7296kHz, ops were in USB mode. Just an observation. Someone, around the AM portion of the 75M band, 3880kHz, is trying Yaesu's digital C4FM mode. They must be using the FT-991A, since it can do C4FM in HF. I have the FT-70D VHF / UHF C4FM HT, so it might me interesting to see if I can up-convert 3880kHz to 2M to decode that. (It would make for an interesting experiment.) 

Title: Re: USB trend noticed on both 75M and 40M? As well as C4FM.
Post by: Rob. on March 21, 2022, 1735 UTC

I know that the ops in the upper part of the 40m band use USB so that they don't interfere with and/or reduce interference from AM ops between 7290 and 7295. I've seen it a few times on 75/80m as well with ops trying to avoid interference from a nearby SSB QSO. Sometimes they do it to be different. The mode choice is just an agreement so nothing to stop them. I've heard FM on those bands once in a while, too.

Title: Re: USB trend noticed on both 75M and 40M? As well as C4FM.
Post by: RobRich on March 21, 2022, 2222 UTC

I am surprised someone running FM on 3880 is not flattened by the usual big-iron AM enthusiasts around 3880-3885. As in legal limit plus PLENTY of "headroom." o.0

I often spot USB ops on 75m when doing a quick skim at night. I wanting to say usually around 3819-3820, but YMMV.

QRM can cause ops on a frequency to just switch to the other sideband instead of QSYing, too.

Also IIRC, older mil-spec PRC radios do only USB for voice on HF, and there are (were?) established nets and meeting spots for them.