Sorry for another partial thread change (:
Over the years I have been quite surprised with how well FM works compared to
SSB when contesting. At first I thought perhaps my equipment wasn't working
well on SSB, but I have noticed other operators having similar results.
Yes SSB is better than FM but in practice I don't think it is as better as some
people believe / communications theory might lead one to believe (at least in
my part of VE7Land.)
73
Mark S
VE7AFZ
mark@alignedsolutions.com
604 762 4099
> On Feb 26, 2020, at 11:04 AM, JamesDuffey <jamesduffey@comcast.net> wrote:
>
> Alan - Sorry I can’t help with your FT991 issues, but if you don’t mind me
> hijacking the thread a bit, I would like to say a few things about weak
> signal contesting using FM.
>
> Below the capture threshold, usually about 10dB signal to noise ratio, FM
> behaves much like other signals with amplitude, not frequency, modulation.
> That is, there is a linear increase in demodulated signal strength for a
> linear increase in input signal strength up to the capture threshold of about
> 10dB SNR or so. So, there is usually useful communication ability if the
> squelch is lowered to the point where it is ineffective in squelching the
> noise. You can usually hear the station. The downside to operating in this
> region is the increased bandwidth, which results in increased noise.
>
> I have had many long distance QSOs on FM operating below the capture
> threshold, mostly in AZ during the January contest when SOTA stations often
> operate from mountain tops with low power handhelds. I remember one QSO of 90
> miles or so on 1296 where the other station was having trouble hearing me.
> After several go around, someone on frequency, who could hear both of us,
> kept telling him to turn down his squelch. He finally did and we made the QSO.
>
> About the only time I operate FM is during the contests, but I find listening
> to a squelched radio unnerving. I expect to hear noise in the receiver when I
> stop transmitting. It seems unnatural not to. How do you know it is working?
> - Duffey KK6MC
>
> James Duffey KK6MC
> Cedar Crest NM
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