Is is possible to repair a hairline crack in semi-rigid coax?

[eb4fbz]

What about using conductive (silver loaded) epoxy?

[joeqsmith]

Fill the crack with SMT paste and reflow? Molten paste will fill the gap down to the inner side of the shield.

I was assuming the OP's cable was aluminum.  I was using a silver plated aluminum to try and replicate what they had.  All of my attempts to solder it didn't work out.  The epoxy and other conductive coatings is an interesting idea.  It may have worked better than anything I tried. 

Of course, I really have no way to know how any of my attempts would effect their equipment's performance. 

[glenenglish]

Remember....
currents flow on the inside of the shield. - copper tape etc on the outside will create an impedance bump.
Now, if you are working at < 5 GHz, and with less than lab gear, you probably will not notice or detect the impedance discontinuity.

If it is > 5 GHz and expected to be > 14dB return loss, you'll need to fill it.
I would suggest pure tin, or tin-silver solder if it will take solder,
Per coppercone's comment, dont use gallium, mercury  or some other liquid metal.
Problem with aluminium is it oxidizes and will, over time develop an open circuit. the liquid metal might prevent this, I dunno

There are also some aluminium solders.
Silver loaded epoxy tends to be quite low in conductivity, try it.....
To test, measure the VSWR at something like 5 to 10 GHz.  (known good load on the end)
Of course, at low frequencies (< 3 GHz), the copper tape will stop it leaking...
Assuming not aluminium. Try soldering it. use lots of flux as required
There are low temperature solders that can be used (lead free) that melt around 165 deg C...

[coppercone2]

gallium sinks into aluminum and turns it into a cookie brittle (casting), or for better aluminum it looks like it got splashed with some xenomorph blood

I put a drop of hot gallium on a bit of aviation aluminum and was able to carve a quarter sized crater in it within a few hours

and they painted luftwaffa aircraft with mercury so their wings fall off in ww2 sabotage, supposedly


I strongly suggest keeping liquid metals away from your test equipment unless its a engineering nickel plating and your only interested in 10 years of life

[TheSteve]

Silver/copper conductive paint? It works fine to make a 26 GHz horn antenna. Any repair will be a crap shoot unless you can verify performance with a VNA though.

[glenenglish]

@coppercone
Thanks for the comments on interactions of Al and Ga. had forgotten that. yes, indeed.
How hot was the 'hot Gallium ' ?

[coppercone2]

i dripped a chunk on it and ran a small jewlers torch (butane) on it for a few seconds to melt it, so not very hot because you won't heat up a aluminum plate much with a torch (3/32), I also scratched it with a scribe under the galllium.


Its not as spectecular as youtube leads to to believe, but its at least as bad as dripping a bunch of hot acid on it or something. I think youtube results are mostly from casting aluminum, which allows for gallium infiltration (weak crystal structure) and becomes very brrittle. A aviation sheet that is like rolled is kinda more like a 'forged' substance I think, which limits it to surface infiltration