Thursday 26 February 2015

Anglian 2m Transverter

A while ago I populated the pcb for my G4DDK 144MHz Anglian transverter. I finally got round to putting it in the tinplate box and tuned it up. All was well, so I decided to put it in a cabinet along with the 8W power module mounted on a heatsink on the back panel. I found a couple of cheap Metal boxes at (unfortunately they have not stocked any for the last 2 years!) A metal plate would be needed for the inside of the box to mount the modules on, I found one off ebay that could be cut to size. Note that as supplied there is a lot of "paint to paint" contact between the metal box parts, so a lot of scraping was done to get "metal to metal" contact to help screening. To further help, a piece of ali angle was mounted between the back panel and the chassis plate (as can be seen in the lower picture:-

To add heat transfer, I wanted to mount the power module directly on the heatsink rather than mount it on the back panel then on the heatsink. To do this I would need to make a rectangular hole in the back panel. Discussing this at the Malvern Radio Club, it was recommended I used a nibbling tool. I found one on the internet for 9.00 shipped. It is a brilliant tool; I can see a lot of use in its future!

As there is no conductivity between the metal parts of the case due to the paint a lot of time was spent removing paint to allow good electrical contact between metal surfaces. I also add a piece of ali angle between the back panel and the chassis plate.

The transverter was setup so that 0.5mW from the K3 on 10m produced 7W on 144MHz, which is the ideal drive level for my amplifier

The 144MHz connectors were spaced to allow an external coaxial relay to be attached with a pair of BNC to BNC male adapters. This allows use with a single antenna feeder if needed. Normally when using a masthead preamp the two connectors are used, eliminating the prospect of transmitting up the back end of the preamp

updated nov 2017

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