[VHFcontesting] SOLVED!: DB6NT external LO weirdness ..

John D'Ausilio jdausilio at gmail.com
Tue Aug 31 15:39:53 PDT 2010

Well, I figured it out just now .. I *thought* I had everything
powered from a single supply (like it would be in the Jitney) .. but
the *reality* was that I was powering the 5/10 box with a different
power supply, on a different circuit. Evidently this caused enough
ground action to make problems for me .. once I actually connected
everything to the one PS it's playing just fine.

Tnx, Mike ... u didn't identify the problem, but you did alert me to
look for such things :)

de w1rt/john

On Mon, Aug 30, 2010 at 10:32 PM, John D'Ausilio <jdausilio at gmail.com> wrote:
> Since the beginning of the year I've been working on converting all of
> the microwaves in the Jitney to a central LO system based on the
> AD9912 DDS + Xtof's XLOCK. I've converted 1, 2 and 3 GHz DB6NT
> transverters by simply removing the crystal and associated caps and
> feeding around +10dBm into the source of the SST310 as described in
> the documentation and these have worked without issue.
> Having enough time before the 'test with everything else working, I
> decided to convert 5 and 10 which live up on the mast. I had already
> run extra cables for the LOs in June when I also needed to add a
> couple runs for 24, and I tested these thoroughly .. they're RG174 and
> at the highest LO frequency they lose 2db, no big deal as that leaves
> me +7 or so at the top of the mast. Xtof has the same transverters and
> shows good output with LO all the way down to 0dBm and below. I've
> also tested the IF cables at 144, no problem there.
> So I cabled it all up, turned it on, and hear nothing on 5 or 10. I've
> spent a couple of evenings tearing things apart, testing cables and
> connectors, and generally tearing my hair out. I've been concentrating
> on 5G .. if I put the crystal back in, beacon booms in around 30KHz
> low where it usually is and everything is great. Take the crystal back
> out, feed 117MHz LO from the 9912 in, and nothing. Tried better
> quality LO cable (LMR100), +9 at the box, still nothing. Replaced the
> 100pf coupling cap, no change. Tried a 56pf, no change. No noise, in
> fact the IF gets quieter when you connect the transverter.
> Unfortunately I have limited test equipment .. a power meter and some
> attenuators, a 600MHz counter (no preamp, needs around -10), and a
> weak signal source for rx testing ..
> I'

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