This was a very good write up - thanks -
With the advent on "spectrum analyers" and panaraomic displays with the new SDR radios they provide a very telling visual fade pattern on even narrow FSK modes on HF - as you said you could actually visualize the antiphase moving up and down in freq and having the affect on each tone.
I dont know but 500 seems to have some of the worse fade characteristics, not too slow and not too fast - just plain difficult for the info rate for some modes (:-) Funny but I never remembered the fading as much when I was at sea on CW/MCW...
As Alan has pointed out the phase/antiphase cancellation on multiple iono paths can ruin hours worth of listening on 137kHz and relatively small changes in location (a few Kms) can show diverse signal reception levels on some nights.
Long haul pretty good at the moment - DCF39 some 45-50dBs above my neons and other restaurant Christmas tree flashers on peak - the normal about 15-20 min fade pattern.
Laurence BY3A-KL1X Tanggu OM89UA
ps Scott VE7TIL made it here on 40m WSPR last night :-) on the probe
> Date: Tue, 30 Dec 2008 01:11:19 +0100
> From: [email protected]
> To: [email protected]
> Subject: Re: LF: 500KHz QSB
>
>
> Hi Gary!
>
> Yes fading seems to be very selective.
>
> Have you ever been listening to a distant AM radio station? Give it a try :)
> There it is often audible, that a "fading notch" travels through one sideband down to lower modulation frequencies, then there is a moment of often terribly distorted audio due to the notched out carrier (the remaining sidebands "virtually much overmodulated"), then the "notch" goes further through the second sideband (if this also passes your filter).
>
> The fading is fast on shortwave, where almost all the time different skywaves "are fighting each other" , medium fast on medium wave, and in the case of longwave transmitters sometimes very slow (may take minutes).
>
> Here in Berlin this longwave radio QSB appears very nicely at dusk to the 204km away "Polskie Radio I" 225kHz transmitter. The skywave becomes stronger and seems to equal the value of the groundwave, so constructive and destructive interference takes place.
>
> Have a nice evening :)
> Dennis
> DL6NVC
>
>
> --
> Psssst! Schon vom neuen GMX MultiMessenger gehört? Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger
>
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