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Re: Topband: Spurs

To: topband <topband@contesting.com>
Subject: Re: Topband: Spurs
From: Dan Zimmerman N3OX <n3ox@n3ox.net>
Date: Thu, 21 Apr 2011 09:59:19 -0400
List-post: <topband@contesting.com">mailto:topband@contesting.com>
>
>  It would appear that a strong sig on 25m
> and another on 31m could produce this effect. My  8 circle receiving
> array elements are 23.5 ft long and are resonant somewhere around
> 10 mHz so would deliver strong signals from both bands. The spur
> seems to be caused by overloading in the rx preamps as it was not
> on the tx vertical.
>
> has anyone else noticed this?


Sort of.  I have one like that 1830  that's strong local AM BCB on 1500
mixing with CHU on 3330.

It's usually not very strong and I didn't identify it until it got really
bad and I heard the distinctive "pings" of CHU and then found the AM station
on another radio.  It would come and go for a while, and I think may
have often been there as a weak signal because of slight preamp
nonlinearity.

But one night it got really strong and started bursting in and out.  That's
when I discovered that the strong, troublesome mix was happening in the
bearings on a cheap rotator I was using under the mast holding my 20m Moxon
rectangle.  I fixed it by putting a ground strap across the rotator.

73
Dan
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UR RST IS ... ... ..9 QSB QSB - hw? BK

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