[K3PZN-List] Lightning, antennas, and coax

Fri Aug 19 10:35:48 EDT 2016

Kyle,

Andy has given you some good advice.

Here's what I think so you can move forward

First, if you did not take a direct hit it is unlikely that the coax or antenna were damaged by lightning. The more likely culprit is the wind. Look for a disconnection especially near the center of the coax to antenna feed.

Second, Test the rig with another antenna even a long wire connected to the tuner may help but if not simply connect it to the rig so you can hear the difference between no wire and wire going into the rig.

This will tell you that all is well with the rig. (I've used a banana plug on the end of a wire to plug it into the SO239 connector)

Do the same thing with the tuner, if it can tune to any frequency/ham-band with your long wire then all is well with the tuner. If it can NOT tune the long wire read the manual for the tuner to be sure it has that ability, if it does and you've done it correctly then there may be something wrong with the tuner.

Once tuner and rig are confirmed good then the only other place it can be is from tuner to the ends of your antenna.

Third, If you have a spare piece of coax hook it up to the antenna and see if all is back to normal - if it is then check the old coax again hooking it back up top the antenna. It make have just shaken loose and reattaching it will bring everything back to normal.

If the coax is soldered to the antenna then temp solder another piece in parallel to it & try that. This is not the best but if it can be done I'd do it rather than unsoldering or cutting the old coax off.

Point, the soldering of another pieces of coax onto the old connection may fix a cold solder joint so if the new coax works just test the old again by plugging it back into the tuner.

Oh, there are methods to tune antennas using short pieces of coax attached & properly terminated so even a long piece of coax not used but still attached may well act as an tuning stub & cut out some frequencies and enhance others so test every band you can work and is ANY of them tune up and you have plenty of QRN then the connection is probably good and the other coax is probably good. After all, if it acts like a tuning stub it is correctly connected.

Forth, If nothing works so far then there is probably a connect issue with the antenna or even the antenna has been broken in places, which in most cases should be visually evident. But, small wire can break within the wire covering which still holds it together, this usually make an intermittent mess up & down the bands.

I once had a bad center connection coax to 80/40m dipole which when I transmitted sent RFI into our TV, the old analog TV, probably ~ 20 or more years ago.

73 de ke3fl,Phil
AEC Carroll County OES, ORS, & VEARRL Life Member
http://cs.yrex.com/ke3fl
Karras' Corner: http://cs.yrex.com/ke3fl/KarrasCorner.htm

      From: "k3pzn-list-request at mailman.qth.net" <k3pzn-list-request at mailman.qth.net>
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Message: 5
Date: Thu, 18 Aug 2016 21:16:25 -0400
From: Kyle Thornton <kyle.3599 at outlook.com>
To: "'Carroll County Amateur Radio Club'" <k3pzn-list at mailman.qth.net>
Subject: [K3PZN-List] Lightning, antennas, and coax
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Hi All,
So with all the storms that have been rolling through the area lately I
think I might have myself a slight issue. I have a terrible feeling that at
minimum my HF Wire antenna strung up in an inverted V formation @ 30ft is
fried if not close to it and the HF coax fried as well. Im not 100% sure but
I think something is up. The HF radio has a built in tuner (480 SAT) and is
usually wonderful at tuning certain bands up to 20m then is not able to.
Antenna is 52ft long (Junior G5RV from MFJ) and is cut to to tune 40-10. For
the jobs that the internal tuner can't do I have a jumper going into an
external tuner. Technically everything is running through that jumper and
into the tuner but I keep it switched to bypass the tuner when not needed.
When I do need the tuner I flip it to where it needs to be adjust some
things and boom I'm on 40, 80 with some work, and 160 with tons of work. It
works perfectly. Up until these storms. Most of the storms I was able to get
down to the shack and disconnect the coax even though everything is below
roof line with plenty of other objects such as water towers for lighting to
strike. From what I can tell I never took or came remotely close to a direct
hit even though there was visible strikes no more than 2 miles away. Since
the radio won't even tune 10 anymore much less any other band could this be
sign or fried coax and antennas or could it be a failing internal tuner? How
do I check all this? 2M side of everything seems to work fine and that
antenna is the tallest one on the mast. 
Thanks!
Kyle  

73 de KC3FMP - FM19KJ

------------------------------

Message: 6
Date: Thu, 18 Aug 2016 22:17:41 -0400
From: Andy Leeds <wo3l at comcast.net>
To: k3pzn-list at mailman.qth.net
Subject: Re: [K3PZN-List] Lightning, antennas, and coax
Message-ID: <5939e982-0d05-519c-0f06-0a1604897fc9 at comcast.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

What this boils down to is devising a troubleshooting plan so that you 
eliminate components as the issue until you isolate the one (or more) 
that are causing the problem. Before doing anything super technical I'd 
start out with a physical inspection of the antenna and coax, looking 
for deformity, burns, etc. Connectors and where the coax touches or 
comes closest to the ground are the first places to look. Even without 
electrical damage a tree branch or flying debris may have hit the 
antenna and damaged it.

Once that's clear you need to start isolating components, probably the 
simplest way to go here is to put a dummy load out at the end of the 
coax where the ladder line starts. You should have a pretty perfect 
match across the HF spectrum.

For the built in tuner a 75 ohm coax jumper before the 50 ohm load 
creates a mismatch ~1.5:1 that the tuner should easily cope with. I've 
got a piece or two of 75 ohm laying around you can use for this.

With your description my first bet is the antenna since the behavior 
with the external tuner has changed as well as the internal one, but 
that's a guess.

Andy