To do this, is really simple. You simply make a box with some high power, high value resistors in it, with connections for the antenna wire, the feed to the radio, and a connection to earth. Most people would do this using a little die cast aluminium box.
I wanted a design that did two things, 1. Used military connectors and would look the part next to other military radio equipment, and 2. wouldnt eat into my small stock of now very expensive die cast boxes!
Something that is much cheaper than a die cast box, is a Clansman 4W SURF unit!
As I had one spare, I decided I would remove the electronics, and repurpose it! The electronics, which include a beautiful silver plated air spaced variable capacitor, have been retained for spares.
The empty case has quite a few mouldings that make deciding exactly how to repurpose it a bit tricky! It turns out that the dehydrator plug hole is far too deep to insert anything in, and the meter hole far too wide. The hole for the tuning control though, was only a little too deep - but accessible! Its the little stub of aluminium that can be seen on the top left of the picture at the left end of the central divider. Ten minutes work with a file had this stub removed!
As I wanted two ground terminals, I decided the other should go below and slightly to the side of this hole, and so drilled a new hole for it. Here I made a little mistake as I didnt notice that internally this point in the case is sloped! Plus, it meant the nut was underneath the stud for the lid fixing, but I managed to get it tightened up successfully.
So here it is so far. Two ground terminals installed. The upper terminal is a sprung push type D10 terminal, salvaged from a defunct CRS/LR box. I had a bit of a shock when I opened this box and found it wet inside! Odd for a sealed box! I believe it to be water, but there were a lot of odd white crytsals inside as well! The other terminal is a screw type insulation piercing D10 terminal taken from a defunct PTC404 field telephone.
The electronics removed from that PTC404 are shown above. The build quality of these field telephones is absolutely superb!
The CRS/LR box and the PTC404 were part of a batch of kit I picked up today from Dominic at LRseries surplus. This batch included the antenna elements, base, and cables I need to get the TUAAM working, plus an EVHF antenna to play with, and a few spare audio plugs, to use to make up test leads.
Another item in the batch was a damaged battery extension cable. Much of the cable itself had failed, seemingly due to fuel or oil exposure. I found about 2ft of it that was usable, cut it out, and set to making it into something useful
The connector ends turned out to be filled with soft silicone rubber. This had to be picked out (easy enough) before I could access the terminals.
With the good cable reinstalled into the radio end connector, A couple of spare 4mm plugs later and I now have a very useful external power connector. I can now easily connect radios up tot he bench variable PSU for testing.
Despite everything, once I was home from LRseries, I thought of loads of other stuff I should have got! I also think I might want a couple more D10 terminals than I have! So looks like i'll have to go back again in a week or two!
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