[TowerTalk] RFI Broadcast Station Mixing in Crank-Up tower?

Rich Hallman - N7TR rich at n7tr.com
Tue Oct 20 12:45:09 EDT 2015


I have tried shorting the rotor wires to the base section of the HDX689 with no changes.  I also would turn the antenna with no changes in the mixing, thinking it might have been mixing in the thrust bearing.  The rotor is a M2 OR2800.

The broadcast station is on 780kc (KOH) and I hear their audio on the mix I'm seeing.  I also did a video of what I am seeing earlier this year.  I thought the mixing was from a ticRing but that was not the source of the mix as that ring has been removed then replaced with an Alfa Ring.

https://m.youtube.com/watch?v=rZ8gXRKGkxE

Thanks....



Rich Hallman N7TR


> On Oct 20, 2015, at 9:33 AM, David Robbins <k1ttt at verizon.net> wrote:
> 
> I have had to add bypass caps on some rotors also.  many dc controlled rotors like the yaesu g series use diodes in the rotor across the stops microswitches to only allow rotation in the other direction when you are against a stop, those 'should' be shorted unless you are in a stop.... however, the g2700 and g2800 also have a 'near the stops' slowdown feature that has 2 diodes that aren't shorted normally and could cause problems.
> 
> 
> Oct 20, 2015 12:21:53 PM, aa4nu at comcast.net wrote:
> 
> Interesting challenge ... in both situations, have you tried to disconnect
> and ground the rotor control lines and/or any remote switch lines, just to
> see if that makes any difference. 
> 
> I seem to recall Ward, N0AX mentioning how he had to put bypass caps on his
> rotor lines at one time to resolve a noise issue in an older NCJ article?
> 
> "Eliminate Noise Generated by Rotator-Control Boxes N0AX 95 Sep/Oct 35"
> 
> Perhaps a review of that text might help with both situations that could 
> move you toward practical solutions?
> 
> 73 de Billy, AA4NU
> 
> ----- Original Message -----
> From: Bill Parry
> 
> I have the mixing problem and my tower is not a crank up. It is 120 feet of
> Rohn 25 with insulated guy wires. I notice it on 160, 80, and 40. I have no
> idea what is causing it.
> 
> Bill W5VX
> 
> -----Original Message-----
> From: Rich Hallman - N7TR
> 
> Has anyone had any problems with intermittent mixing from a close broadcast
> station with a Crank-Up tower? I think I may have an issue with one of my
> towers. Cranked up I hear mixing all over 80 meters (Every 10
> KC).....Cranked down its gone. I already eliminated the antennas. Mixing
> gets very intermittent in wind as the tower moves around.
> 
> Thoughts about grounding the top section to the bottom when fully extended?
> Was thinking of grounding the coax at the top and bottom of the tower?
> 
> Thanks....
> 
> 
> Rich N7TR
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