[AMRadio] K1MAN comments on disrupting the 75m. AM "Window" (MP3)

Jim Candela jcandela at prodigy.net
Tue Dec 21 15:35:36 EST 2004


    Last night I heard what sounds like DRM on 3880 or
85, and appeared to be 10 kc wide. That was about 9 pm
Central time. It was full scale on my Sony SWL
receiver. Since I am at a new QTH now (Round Rock,
texas) I thought this was local QRN. It was gone this
morning. Now that I read your DRM description, maybe
the AM window has a new problem? Did anyone else hear

    BTW I am months away from making RF again. Maybe
easter time. Way too much to do with our move, and
getting the old house ready for the market.


--- Donald Chester <k4kyv at hotmail.com> wrote:

> > > I'm confused on your commentary (The imaginary
> "AM Window" is another
> > > thing that needs to go.).
> I've heard many AM'ers say that many, many times,
> and I agree.  The vicinity 
> of 3830 is often unoccupied after primetime hours in
> the early evening and 
> the SSB'ers go to bed.  Sometimes a few AM'ers will
> suggest operating down 
> there.  For 2 or 3 evenings, an AM group develops,
> and the QSO goes smoothly 
> and usually QRM-free, much nicer than the usual AM
> frequencies.  After a few 
> days, activity dwindles, and finally no more AM
> activity is heard.  I tune 
> back up to the vicinity of 3885 and there everyone
> is doing their usual 
> thing..
> I sometimes calll CQ on 3830 when it is not busy,
> and most of the time I get 
> no AM  response.
> Down here, when K1MAN QSY's to 3885, it pretty well
> wipes out any 75m AM 
> activity from the Northeast.
> Lately, I have been operating mostly on 160m.
> >I've got Crystals for 3.970/3.980 & 3.990.  Isn't
> there some broadcast 
> >station
> >up in that part of the band, as well?
> It looks like we have lost 3990-4000.  For many
> years 3995 has been occupied 
> with Radio Deutche Welle.  They would broadcast on
> AM, so you could work to 
> either side of their carrier unless they were
> exceptionally strong.  But 
> they recently converted to a new digital mode being
> tested for shortwave 
> broadcast use.  It is called Digital Radio Mondiale
> (DRM).  The signal 
> appears as a S0+20dB swath of white noise, with very
> steep skirts.  It is 
> uniformly noisy throughout the entire 10 kc/s. 
> Worse than the old Soviet 
> jammers for taking out a wide hunk of the band.
> There is also sometimes one on 40m, in the vicinicy
> of 7260.
> Wait tilll all the major SW broadcasters convert to
> this mode.
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