Hi everyone out there,
Le 10/10/2020 à 02:17, Paul S. in CT a écrit :
[...] Minor nitpik is that one should tune 1kHz low for USB as the radio ADDS 1kHz to the receiver. Likewise, the opposite occurs using LSB.Not necessarily a bad thing. As I see it this might help keep the filter on the actual signal. Too many receivers, when switched to SSB remain with the AM bandwidth and decode only the wanted sideband, which adds some background noise.
Buttons a bit small, but have that nice indent function sadly lacking on the ATS-405. If you don't need the SSB or "Sync", I'd stick with the PL-310/380.Yes, the PL310/380 receivers are excellent on AM, but as far as the 310 is concerned this applies only to the original version, not the PL-310ET, which is way behind the original version. Unfortunately that one is no longer on the market.
PS: that soft mute question... As far as I know its an Automatic Gain Control function that amplifies the strongest 10db of signal, and reduces lower-powered signals. The problem is that the atmospherics may cause the signal to fade. This causes the soft-mute function to go from a loud signal to a barely audible signal (aka: pumping). Fading normally produces this effect, but soft-mute makes it worse. The SYNC function is supposed to help this by supplying the carrier wave that fades. The problem with THAT is the audio is part of that faded carrier. Many of us here and in the Amateur community are of the opinion that the audio frequencies are NOT affected by the fading, just the carrier. Providing a carrier will recover the audio. Yet another 'can of worms' so to say.OK, now I see what you mean by soft-mute. But mind you, on the PL380 it can be deactivated relatively simply. Here's how to go about it:
1/ press VF
1/ tune the receiver to an unused SW frequency.
2/ press and hold VF
4/ when the receiver starts scanning tune down. The background noise becomes stronger, which shows that this "soft-mute" is no longer active.
Unfortunately it becomes active again when you switch the set off, and so you have do it all over again when you switch it on again.
It might work with other Tecsun models, I don't know. Maybe you could try it with the PL-330. It might also improve the action of the synch detector.
The audio frequencies are necessarily affected by the fading, which is caused by multipath propagation. Two or more signals arrive out of phase which causes a sort of notch that creeps through the bandwidth, just as if you were using a notch filter. Of course this just changes the tone of the audio and does not cause the distorion you get when the notch reaches the carrier itself. That change of tone will be more important if the notch is wide and go almost unnoticed if it is very narrow.