Topband: Rotator creating spur on 1820

[k8gg at voyager.net]

Jerry, et. al.,

I didn't have the problems from my own installation, but I used to live
about 1/2 mile from an AM 930 station and there would be a 2nd harmonic
spur at 1860 and a mixer spur of 2 x 1400 - 930 = 1870 KHz.  W0CD helped
me find & build hi-pass filters in old ARRL Handbooks for my RX antennas. 
The only way I could check the SWR was to turn the transceiver down to
about 2 watts and feed the beverages or pennants and scan the band to make
sure the terminations, etc., were OK.

I have repeatedly missed a couple of 160 contest stations in the former
Yugoslavic area because they would run on 1870.  Even 4+ miles away at
W8TOP in the CQ160 CW Contest there was no way for us to listen thru the
harmonic mixer.  There was always some diode rectifications off site so to
speak.  We suspect old support towers for FM stations and a nearly
abandoned AM station between the AM930 and W8TOP, but, since the spur is
not on site, we just live with it.

The suggestion of a jumper across the rotator makes good sense if some
dissimilar metals in the unit are making the diode.

GL,  George,  K8GG





> Likely all the spurs you see on 160 that are caused by AM stations will
> land on 10 kHz increments because the stations are spaced on 10 kHz
> increments.  I identified one of the stations that was a big contributor
> to my problem and that was on 1730.  I haven't found the other station
> yet.  I expected the station on 890 to be a contributor since it is only
> 1700 ft from my antenna but I don't think it is the one.  (It is a
> contributor to the spur that happens on 3510).  Regardless of which
> stations are involved, the main problem is that the mixing is being
> created near my rotator, and probably inside it somewhere.  I have to
> kill the mixer somehow. More than likely the stations are clean.  It
> will be interesting to see if the same mixer is causing both spurs, 1820
> and 3510. Fortunately the 3510 spur goes away at night because one of
> the contributor stations is daytime only.
>
> Interesting video by N8PR, but he is fighting a different problem from
> what I have,
>
> I do not have a strap around the rotator.  That's worth a try. Thanks
> Lloyd and Hank.
>
> Jerry, K4SAV
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