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Re: [TowerTalk] rf burns

Subject: Re: [TowerTalk] rf burns
From: chris casey <>
Date: Wed, 22 Feb 2012 20:59:22 -0600
List-post: <">>
I added about 10-12' of window line in, and routed it around rather
than through the tree.So I still get some sorta noise in my headphones
and I can get a much smaller rf burn when I get down to a 1:1 on the
tuner. I have to back off to about 1.4:1 rather than closer to 1.8:1
before to get the noise to go away and the pain in my fingers to stop.
So I'm guessing I'm generating some high voltage in the tuner to
achieve a match and that's whats causing me trouble. That said, some
bands match just fine now, but 40m is giving me trouble tonight.

More progress I guess.

On Fri, Feb 10, 2012 at 5:49 PM, chris casey <> wrote:
> I undid the wrap on the splice and one just fell apart in my hand. I
> got it all put back together and sealed up, noalox'd the outside plugs
> and sealed those up with tape and silicone.
> I still get some noise in my headphones when tuning up but not near as
> much, and my key base no longer tries to kill me when I touch it.
> Definite progress.
> I didn't have time to add length to it and go around the tree rather
> than through, but this gets me going again. Only to find noise and
> fading signals at the moment, but a happily loaded antenna.
> Thanks everyone.
> On Tue, Feb 7, 2012 at 11:30 AM, K0DAN <> wrote:
>> Make sure all the banana plugs are making good contact (remove + clean +
>> squirt of Deoxit), and that your splices are clean and making good contact
>> (I would recommend twisting them, then soldering them). Remove the feedline
>> from the tuner and put an ohm meter across should measure a fairly
>> low resistance.  If the loop or feedline has opened up, you no longer have a
>> closed loop, and that could definitely bring high RF back into the shack.
>> Bonding all your equipment to a single point ground is also important.
>> GL es 73
>> dan
>> k0dan
>> -----Original Message----- From: chris casey
>> Sent: February 06, 2012 11:31 PM
>> To:
>> Subject: Re: [TowerTalk] rf burns
>> Rig goes to tuner with a couple feet of flexible "big" coax of some
>> sort, not the little rg-58 type, no reducer needed for the connector,
>> but not sure what specific type of coax it is from my vantage point
>> nowhere near my operating position at the moment...  to the tuner, a
>> 1.5KW MFJ without the roller inductor, but it has served me well over
>> the years. From the balanced binding posts goes 450ohm window line, a
>> couple feet to threaded brass rod to pass through the back of the
>> desk, and then a few feed with banana plugs to go through a pair of 6"
>> double female so-239 headed through a blocked off window. Outside
>> another set of banana plugs  which then run out and through a pine
>> tree and to  a closed 80M-ish loop around the back yard.
>> There is a splice as the length was pruned for one years sweeps
>> operating position and extended for the next as I always ended up
>> somewhere else, garage, laundry room, travel trailer, screen porch
>> etc.
>> My splice technique is to cut out a section of solid spreader, twist
>> each conductor over the opposite to lay fairly flat, solder, well
>> overlapped heat-shrink, then drill a couple holes on each side of the
>> spreader i cut and small zip tie it at the splice joint which keeps it
>> from twisting and collapsing in. It sure looks like it should work ok,
>> you can't spot the splice at a glance from any distance. But it sure
>> is a place to look for a failure, if it had a bad solder or something
>> it would likely stay fairly solid with the twist and be flakey. Banana
>> plugs are soldered on as well.
>> I have tried to find what a western union splice is but I couldn't
>> believe I couldn't find a good explanation. Just lots of references to
>> it. But I havent tried for a few months, seems like it shouldn't be
>> that hard.
>> I know there are "bad" lengths of balanced line to avoid, but I have
>> no idea how long my feed line is also as its been adjusted to fit
>> spaces not to fit any measure.
>> I didn't think one had common mode currents on balanced line like you
>> would find on unbalanced coax.
>> I'll re-work the splice and check the plugs, see what I can see.
>> On Mon, Feb 6, 2012 at 9:17 PM, Robert Carroll <> wrote:
>>> I don't know the exact design of your antenna.  But assuming it is a
>>> continuous loop and not open anywhere except where the feed-line connects,
>>> I'd ship an amp or so dc down the feedline (at relatively low voltage) and
>>> watch the current flowing. It should be pretty constant.  If it drops
>>> off--or if you don't have continuity to start with--you may have a bad
>>> joint
>>> somewhere or a broken conductor.  I ran into that once with a loop where I
>>> had to solder several pieces of wire together.  One of the soldered joints
>>> had become defective and the dc (as well as the rf) impedance was all over
>>> the map.  I have had similar problems in 450 ohm line--and I have plenty
>>> of
>>> splices in all my 450 ohm line.  I recommend (if the line is solid) using
>>> the Western Union splice, soldering, and coating with liquid tape.
>>> Bob W2WG
>> _______________________________________________
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> --
> -Chris



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