Topband: Rotator creating spur on 1820

[Lloyd - N9LB]

Do you have a heavy gauge flexible strap jumpering the mast pipe to the top
of the tower?

The mast pipe must be at the same electrical potential as the tower.  The
thrust bearing and rotor motor probably is not a low impedance path.

I use the commonly available 1 inch wide woven braid / ground strap material
to connect my mast pipe to the top of the tower.  It runs parallel to my
coax rotor loop at tower top ( about 24 inches long ).

73

Lloyd - N9LB
 
> ----- Original Message -----
>
> From: "K4SAV" <RadioXX at charter.net>
> To: topband at contesting.com
> Sent: Thursday, November 2, 2017 2:40:49 PM
> Subject: Topband: Rotator creating spur on 1820
>
> I have a problem for which someone on this forum has the solution. I 
> know that because I have seen that message sometime in the past.
>
> The problem is that my rotator is rectifying a couple of AM station 
> signals and creating a spur on 1820. It's normally pretty weak on my 
> receiving antennas but sometimes it's a problem. I found that if I 
> listen on my XM-240 near that rotator it can be very loud. As soon as 
> I move the rotator it causes the spur to go away, or become weak. A 
> few minutes later it is back again. It pops in and out.
>
> So who had the problem and how did you fix it?
>
> Note that my XM-240 actually shows a low SWR on 160. That's because 
> the
> XM-240 balun doesn't work well on 160 and the common mode currents on 
> the feedline couple to the tower and the tower becomes the real 
> antenna on 160. So in this case the tower is the antenna and it has 
> that rotator cable against it picking up max signal from that cable 
> (also radiating it to my other antennas). No, the XM-240 is not used 
> on 160 (except to find the source of this problem).
>
> The rotator is a Yaesu G-2800DXA.
>
> Jerry, K4SAV
> _________________
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