Clean That Magmount!

I've recently gone back to doing some portable working from the car using a 20m AmPro vertical.  At £19.99, these are really very good value for money and, being just a wire up a stick, work well. 

Except, I've been having some problems.  First, the SARK-110 analyser was refusing to give sensible results.  There was a lot of noise on the signal, and I just couldn't approach a correct SWR reading.

Resorting to a simple analogue SWR meter, I found a good match, but then this went awry when I tried to key up at the rig.

It seemed like the magnetic mount, one of those Chinese three-magnet units, was at fault.

Many people report that these Chinese magmounts rust very quickly indeed.  I can confirm that this is so, which is very annoying and typically lacking in attention to detail.

Baby, I was born to rust...

The metal bar that connects the front two magnets with the rear one, and which forms the mounting point for the antenna, is aluminium.  Newer models tend to have a single fixed plate between magnets now, but the corrosion is much the same.

On removing the coupling where the coax is joined to two concentric rings (one for the sheath, the other for the inner), I found a good amount of aluminium corrosion, which I suspect was hastened by dissimilar metals (the coax coupling is brass.)

I cleaned all the connectors with light sandpaper and a stainless steel kitchen scourer (don't use normal steel wire wool - it will leave infinite amounts of rusting metal in your coupling - and probably lead to electrical shorts.)  A spray of WD40 and then cleaning this off with paper towel, and then the application of some aluminium conducting grease, avoiding any short between inner and sheath connectors (£6.00 from Innovantennas), completed the job.

I'm afraid that I didn't take any photos for lack of time, but don't be afraid to undo that coupling from coax to antenna mount - there is nothing to fall apart and it is quite robust to be handled roughly.

Suffice it to say that these units are not at all ideal for permanent exposure to the elements in countries that are anything other than deserts.  If you want a good mount for UK weather, you probably need to look at a drilled-in unit of some sort. Otherwise, you can just remove the magmount after each use, though these units do moderately scratch paintwork over time.