Wednesday, July 31, 2013

Lunchtime QRP continues to be successful

My lunchtime QRP sessions continue to be a success with QSOs all over the world.  SOTA stations, special event stations, DX stations and rag chews all have been making it into the log.

Last week, I mentioned bringing my mag mount into the house to replace the PL-259 connector.  Thinking about that, I realized I had neglected maintenance on the other end, even though my high SWR problem was cured last week.


The coax at the business end goes into a plastic assembly. The center conductor is securely soldered to a ring which makes contact with the hex sleeve that holds the radiator - a Hamstick, or in my case, my Buddistick.   The shield, however, makes only physical contact with the metal of the mag mount.  The shield braid is pig tailed and is sandwiched in place between an insulator (which insulates the radiator from ground) and the actual metal of the mag mount frame.  There is no electrical soldered connection, per se - just physical contact and the pressure to keep it in place is provided by the main through bolt.

So tonight, I took it apart.  I took a metal kitchen scrubbie and cleaned the metal of the mag mount frame and also scrubbed the shield copper.  It is amazing what kind of crud and garbage builds up in there from exposure to the elements over the years.  Now, even though it is still only physical contact, at least the metal has been shined up and minimal resistance has been achieved.

The other thing I did was to drill two holes into the frame of the mag mount, so that I could cable tie the coax in place against the metal strut.  This will act as an added strain relief to prevent the coax cable from flexing around a lot and causing metal fatigue and possible shield or center conductor problems down the road.

72 de Larry W2LJ
QRP - When you care to send the very least!

1 comment:

Graham said...

good day Larry,

I use a product called Pentrox on any joints as you describe for your coax braid to mag mount and for that matter on any metal to metal joints on any antenna.

Pentrox is a petroleum based product which contains fine zinc particles. The petroleum provides the anti oxidation and the zinc particles ensure a good electrical connection. It also works very well as an anti sieze agent so that you can get the parts apart later on.

Pentrox is only one such product and is common at any electrical supply. Home Depot and Lowes sell similar products.

cheers, Graham ve3gtc