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Re: [RFI] Broadcast station RFI Mixing - RESOLVED

To: "<k1ttt@arrl.net>" <k1ttt@arrl.net>
Subject: Re: [RFI] Broadcast station RFI Mixing - RESOLVED
From: Rich Hallman - N7TR <rich@n7tr.com>
Date: Thu, 29 May 2014 14:06:12 +0000
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Included with the grounding suggestions, I ordered two 1/4 inch sheets of EPDM 
rubber sheets that are uv resistant and are designed for 1200 psi.    I'm going 
to lay these sheets in the tic ring tray that the boom mounts in to insulate 
the boom from the rotating ring to see what happens.  

I'll let everyone know how that goes this weekend.     Thanks....

Rich Hallman, N7TR
Ex.  KI3V, N3AMK, HL9RH, A92FN

> On May 29, 2014, at 4:37 AM, "David Robbins" <k1ttt@verizon.net> wrote:
> if you don't have a grounded driven element so the coax braid connects to the 
> ring through the boom you should probably run a ground wire from the tower in 
> parallel with the coax but connected to the boom/ring.  this would be the 
> case if all the elements were insulated, you would essentially have a boom 
> picking up rf and possibly rectifying it through the bearings or motor... 
> probably not the best case for lightning, and may even cause problems with 
> corona discharge through the bearings or motor also.
> May 29, 2014 07:23:59 AM, john@kk9a.com wrote:
> I had a very similar situation when I had my 160' tower loaded with ring
> rotators near Chicago. It had a homebrew 80m rotating dipole on top and I
> heard a mix of local broadcast stations on this band. 40m was fine. I
> never found a solution except for using a separate RX antenna. I assume
> that my rings are grounded though the motor and from touching at least one
> of the side bearings however I never verified this and there are many
> variations of TIC rings. This would have definitely been worth trying!
> GL
> John KK9A
> To: "rfi@contesting.com" 
> Subject: Re: [RFI] Broadcast station RFI Mixing - RESOLVED
> From: Rich Hallman - N7TR 
> Date: Mon, 26 May 2014 17:52:43 +0000
> After several months of looking for the broadcast mix I finally purchased
> a HF
> Direction Finder from http://www.nationalrf.com/type_hfdf_vector.htm. This
> really helped me pinpoint where the noise was generating from. What I found
> was with the HFDF unit and listening to the loud mix on 3.900, I tracked it
> down to the new HDX689 tower I installed last year. I just have a single M2
> rotatable dipole up and figured it has to do with that antenna. After
> completely disconnecting the antenna and grounding parts of the elements, it
> didn't help. I then began moving the M2 15M6 that is mounted on a new model
> TIC Ring and noticed the noise would get real bad when I rotated the ring. I
> then grounded the rotating platform on the Tic-Ring to the tower and the
> noise
> went away!
> I reinstalled the 80 meter rotating coax and all the cabling while keeping
> the
> rotating ring part of the TIC-Ring grounded, and I have no problems. I
> removed the ground to the tic-ring rotating platform and the noise came back.
> Next question....Anyone have a Tic-Ring that they have had this problem with?
> Im just glad at this point I found my mixing issues.
> Thanks...
> Rich
> -----Original Message-----
> From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Rich Hallman -
> N7TR
> Sent: Saturday, April 19, 2014 6:13 PM
> To: rfi@contesting.com
> Subject: [RFI] Broadcast station RFI Mixing
> Over the past year I have been hearing a local broadcast station on 80 and 40
> meters. 80 meters is the worse. Filters will not help, and sounds like
> there
> is something rectifying. I think I may have a problem on the power pole
> since
> it seems to go away for a day or so after it rains. Also...I have not
> eliminated that there may be a problem at the broadcast site. The station is
> KKOH and is about 10 miles from me...but line of site.
> I did a YouTube video of what I am hearing...and for the most part I can hear
> the carrier every 10 khz...so places like 3900 is real bad. With the
> intermittent connection as it sounds like...it messes up the entire 80 and 40
> meter band. Sounds like a bad connection in my antenna...but I have already
> confirmed my antennas are fine and I confirmed I can also hear the mixing
> on a
> mobile 80 meter whip in the truck as well as other antennas. On 40 its lower
> signal...but also can be heard every 10 khz or so and the mixing is very
> intermittent / scratchy. Seems like its also more intermittent with wind.
> Here is the video... http://youtu.be/rZ8gXRKGkxE
> I just emailed my power company the video as well. Will get the KKOH station
> engineer to listen as well to make sure they don't have an issue with an
> insulator or ground on their tower.
> Any other thoughts?
> Rich N7TR
> ex KI3V, N3AMK, WB3JOV
> www.n7tr.com
> http://www.qrz.com/db/N7TR
> Telnet: dxc.n7tr.com N7TR DXCluster
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