Yes, the f/2 and 3f/2 both track the 20m transmitter exactly, so its not
mixing with some other signal, its all due to that 20m signal somehow.
It is also related to wx somehow. Yesterday when I got it to start at
45w when beaming east/west it was raining, later in the day when it
dried off the threshold went up to almost 500w, now this morning when
it's snowing (about 1" of heavy wet stuff so far) the threshold is about
200w and appears not to be related to beam direction... more hunting to
do but not till the snow melts now I guess.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: Michael Tope [mailto:W4EF@dellroy.com]
> Sent: Saturday, May 18, 2002 04:23
> To: W8JI@contesting.com; 'Amps'; David Robbins
> Subject: Re: [Amps] al-1500 parasitic?? or some other problem?
>
> Tom, I thought Dave said that the 21 MHz spurious signal tracked his
> fundamental and held a 3F/2 relationship with it all the way across
the
> 20 meter band. I don't see how a the 14 MHz fundamental beating with
> a fixed frequency oscillation could do this (Dave was the spur
tracking
> really exactly 3*F/2 WRT to the 14 MHz signal??).
>
> Can a free running oscillator injection-lock to a pump signal near its
> 2nd or 3rd harmonic? If so, perhaps that would explain it? Another
> possibility would be some poorly shielded RF device with a frequency
> divider that is capturing on Dave's nearby TX signal (or one of its
> harmonics). The frequency divider could produce the F/2 component
> which in turn could beat with the 14 MHz signal and to produce the
> 3F/2 component. The fact that the spurious signal is bidirectional
> in its response to Dave's antenna suggests to me that its due to a
> harmonic of his signal that is created either in or before the 20
> meter antenna (I would expect a Yagi to look bidirectional at its
> harmonics, whereas it would be unidirectional at its operating
> frequency).
>
> Interesting problem.
>
> 73 de Mike, W4EF...........................
>
> ----- Original Message -----
> From: "Tom Rauch" <w8ji@contesting.com>
> To: "'Amps'" <amps@contesting.com>; "David Robbins" <k1ttt@arrl.net>
> Sent: Friday, May 17, 2002 6:45 PM
> Subject: RE: [Amps] al-1500 parasitic?? or some other problem?
>
>
> >
> >
> > > Well, I can now say for sure that it is not the amp. I have found
> > > that by feeding only the top 6 ele 20m beam and pointing it either
due
> > > east or west I can generate the f/2 and 3f/2 products with as
little
> > > as 45 watts. The beam heading is not what I was expecting as it
puts
> > > both the 40m and 15m towers off the ends of the 20m elements. The
low
> > > power needed does really narrow it down to something related to
that
> > > top antenna or something very close to it... especially since I
can
> > > not generate them with 1500w to a 4 ele 20m beam 45' below it.
> > >
> > > I can also say that its not the guy wires as the 17 year old rusty
> > > ones were replaced yesterday.
> >
> > Hi Dave,
> >
> > I'm positive you are wasting time looking for non-linear joints
> > producing a F/2 or 3F/2 product. Sub-harmonics are impossible to
> > produce by virtue of a non-linear system.
> > .
> > Look for a mixing product with another local oscillator or signal of
> > some sort, or a spurious oscillation in a device with gain.
> > 73, Tom W8JI
> > W8JI@contesting.com
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
>
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