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Old 23-09-2011, 18:24   #1
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Lightning Strike and Coax Integrity

So we were hit by lightning the other day and lost some electronics. The VHF and dual band radios are toast. I have a question for the radio gurus:

We have 1/2" Heliax coax connecting the radios to the antennas. As you know, this is VERY expensive and high performance stuff, so I am loath to replace it. I would need to buy ~150' of it for replacement.

The lightning absolutely traveled down the sheath ground, as evidenced by blackened connectors and the damage to the wires grounding the radio chassis to earth, but the center feed seems physically fine (won't be able to test continuity until I pull the mast).

So my question is - will I be OK keeping the Heliax if it tests OK with no continuity between core and cover and complete continuity of the core and the cover, respectively?

If not, and I have to replace, what is a good quality coax for VHF/UHF frequencies to change it with?

Mark
(who is happy that the 100' of 1" Heliax connecting the HF and SSB is OK)
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Old 23-09-2011, 18:39   #2
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Re: Lightning strike and coax integrity

Hmm.. well I would always be doubtful of the coax even if it tests OK. As for testing it, it really has to be tested by RF techniques rather than a DC continuity / insulation methods.

In essence you have to send some RF down the coax into a 50 ohm RF load and see how much power is lost in the coax and how much is reflected back.

You will need a VSWR / RF power meter, your transmitter and either a RF dummy load or a know good antenna to check the performance of the coax.

Maybe a suitable replacement would be LMR 400 or perhaps RG 214.
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Old 23-09-2011, 19:28   #3
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Re: Lightning Strike and Coax Integrity

I have a dummy load and could borrow a meter, but unfortunately all the magic smoke is on the outside of my transmitter at the moment and the antennas transmutated themselves into vapor.

I guess I could sell the copper in the Heliax, pay for the LMR 400 and have enough left over to buy a new VHF?

Mark
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Old 23-09-2011, 19:33   #4
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Re: Lightning Strike and Coax Integrity

Do you have a hand held VHF / UHF (or can you borrow one ) to use as the RF source (transmitter). You might need some suitable coax adapters and leads depending on what style of connectors are on the coax and handheld.
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Old 23-09-2011, 19:45   #5
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Re: Lightning Strike and Coax Integrity

Test it but if its black on the shield and your antennas are vaporized and your radio is toasted, doesn't look good to me. If you can afford it or are covered by insurance, replace it.
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