Wednesday, 21 October 2015

Ex-PMR collinears - Preparing to test

It was a bit inconvenient of the riggers to just cut the connectors off, i'll have to say! But, you cant look a gift horse in the mouth, no matter how bad you think its teeth may be.

So, the first task was to get a connector onto one of these antennas. I happened to have some in-line female N-types ideal for the job

With only about three inches of cable to work on, I had to make sure it was right first time! The corrosion hadnt had time to get very far, thanks to our handyman informing me of these being available very shortly after they were decommissioned. Baring the cable back just 3/4 of an inch gave me good clean braid and inner conductors. The connector I had chosen has an insert that pushed into the braid to make the outer connection. With this in place, I trimmed off the excess braid strands, then cut away the excess dielectric.

By now the soldering iron was nice and hot. Tinning the center conductor allowed me to cut it to length for the center pin, which with its PTFE insulator was added next

Before going further, I hoovered up the cut off strands of the braid, and made sure there were none still present that could cause a short. Then, with the aid of a pair of adjustable spanners, the outer body was added and the securing nut tightened on.

So, I now have an ex-PMR UHF 440-470MHz collinear, with a short but usable connector attached, ready to be tested.

I would suggest to the riggers in future that they dont cut the connectors off, but leave the antenna attached, pull the whole feeder off down to the equipment cabin, coil the feeder and antenna up, and let me have the lot!

I need the weather to improve slightly now in order to rig up to test the antenna. Theres a lot of jet aircraft noise today in my area, which unfortunately is overcast, so it seems a good day to scan the UHF airband! Ive already found one active frequency with American accents asking for weather info for various UK airfields. I suspect from the S9 signal strength that this may be an AWACS controlling the exercise.

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