[TowerTalk] rf burns

[Jim Brown]

GROUND is NOT the problem, although you should definitely bond your 
station to the earth and to the service entrance. The "service" ground, 
whatever it is, goes to the power panel chassis, so THAT'S where you 
should go if you can't find what it's grounded to.

As to your RF burns -- you've got RF in the shack because your antenna 
is unbalanced, and causing RF current to flow on the feedline.  The 
easiest solution to that (other than changing the antenna) is to add a 
serious common mode choke at the feedpoint.  A bifilar choke formed by 
winding 14 turns (x2) of #14 or #12 THHN on a #31 ferrite core would 
work quite well.  See http://audiosystemsgroup.com/RFI-Ham.pdf for 
details, and a lot of "why and how it works and why it's needed."

73, Jim Brown K9YC

On 2/6/2012 7:02 PM, chris casey wrote:
> Yeah, so... I've never had a good ground. Right now the tuner and the
> rig are connected by a piece of #14 solid copper, and then the usual
> rig to PS to the wall.
>
> Best I can tell I need to bring my station to a ground outside which
> is also tied to the service ground. But I can't find a service
> ground... So I know I'm exposed in the ground area to some fun.
>
> The thing that I find strange is when I bring this in to the garage,
> or into the travel trailer, and connect things the same I have no
> problem. Yes its a different plug in the wall, so there are places
> where things can be different still. And I took everything apart just
> now, re-routed cables etc some, and the behavior changed but is still
> there... I need a way to check for RF that doesn't involve my
> fingertips. Thats awful.
>
> I see some mention of high voltages created in the tuner and arcing
> etc, but I don't think I'm getting arcing but I'm not sure short of a
> movie style arc noise I would be sure...
>
> Thanks.
>
> On Mon, Feb 6, 2012 at 8:42 PM, Mike N1TA<mike at n1ta.com>  wrote:
>> Hi Chis,
>>
>> What type of ground do you have at your station (if any)?
>>
>> Mike N1TA
>>
>>
>> -------- Original Message --------
>> Subject: [TowerTalk] rf burns
>> From: chris casey<cscvrp at gmail.com>
>> Date: Mon, February 06, 2012 7:01 pm
>> To: towertalk at contesting.com
>>
>> So I haven an 80M loop I usually only get to use for sweepstakes every
>> year, rest of the time the feed line is coiled up in a tree.
>>
>> I have had opportunity to bring it inside and setup a "permanent"
>> operating station. I've had grand fun, but see some weird behavior now
>> and then. When it was wet out a couple days ago while tuning (mfj
>> tuner, 450ohm window line feed) it would bounce all over. And more
>> often than not when I get towards a good match I start getting a growl
>> in my headphones. Tonight I got a doozie of a rf burn off my key base
>> which sets right in front of the tuner knobs. It will do this on
>> several bands, 40m down at the bottom of the band tonight.
>>
>> I have a splice which I figure I'll cut upstream from and add a new
>> hunk in and add some length. Its a bit short and running right
>> through a pine tree, I guess I'll add some more feed line in and go
>> around the tree.
>>
>> Same antenna with same feed line length matched all over the place
>> without issue when ran to the travel trailer for sweepstakes. Now if I
>> don't want nasty noises on TX I have to run an swr above 1.5 usually.
>> I worked HU2DX on 15M and TX6T/P 17M CW tonight on the first call so
>> it must not be just a stub of feed line 10' long to the splice...
>>
>> Besides re-working the splice, and routing around the tree, any ideas?
>>
>>