M0EYT 10GHz system

I've been playing with 10~ GHz radio for quite some time. In 1990 I had a colour TV link to a friend of mine who lived a few miles away - it was full duplex using simple Gunn oscillators and tweaked LNBs on the receive side. The link had stereo sound as well as a wideband audio mode when video wasn't needed. Around 2001 I treated myself to a DB6NT 10GHz transverter. On building up the transverter, I made a quick test assembly to take to one of the May UHF and up contests that our local radio club, FRARS, was participating in. With the bare transverter, a small sky mini dish and a non-matched feed, I worked a station over 400Km!

As can be seen in the above picture, the transverter is wrapped in a layer of bubble wrap then blue cloth, this was done to provide wind proofing for local oscillator stability purposes. Most of the components are fresh air mounted, and the waveguide to SMA transition was not optimised.

The next phase in the transverter project was to add a proper dish and feed assembly. I won a north region sky mini dish, and managed to find some WG16 bends and flexible waveguide, so I made the setup as per the above picture. This setup had a few good runs out on Bell Hill in the 10GHz cumulative contests.

Since the transverter system was working nicely, I thought it was about time that it was properly mounted in a waterproof box in order to provide some protection from typical contest weather. I found a nice sized box at a local electrical wholesalers - its a "GEWISS GW44208 IP56" type enclosure. I made a solid base plate that is fixed to the box, and the various transverter items are bolted to this. The above picture shows the bare transverter, TR relay, a SMA to WG transition of the G3PHO design, and some DC power distribution. Underneath the DC power terminals is a dc-dc converter to drive the TR relay.

The next phase of development sees the addition of a 10GHz PA with an output power around 4~ watts, and to ensure utter frequency stability, one of the excellent G8ACE oscillators was added. The oscillator is housed in a large block of polystyrene and provides an excellent stable frequency source. As per G8ACE's article in the UKuG's 'Microwave newsletter' (now known as 'Scatterpoint') on crystal oscillator frequency jitter and possible solutions, the oscillator module was cycled on and off for about 2 months whilst in a freezer - 12 hours on / 12 hours off. I am convinced that this helped matters a lot, and now gives me excellent long term stability.

This is a picture of my current 10GHz transverter system. I have moved some of the semi-rigid plumbing around to make the interconnects shorter, in particular, the TR relay is now bolted directly on to the back of the WG to SMA transition and a DEMI LNA connects directly to the SMA on the receive port of that relay. Hopefully I can get the NF measured at the Martlesham Microwave round table this year.

The last photo (above) shows the completed system as of July this year. This picture was taken during the 10GHz cumulative after working G3LRP at 397Km. The dish is a 1M offset, bottom fed, with the transverter being visible at the back of the dish. The tripod was obtained from the Newbury rally cheaply and is an ex outside broadcast one - very heavy duty and ideal for mounting dishes on! The tripod does have a calibration ring in degrees, but some some odd reason the degree values are reversed - there is a lookup table taped to the tripod to aid alignment in the heat of the contest.

The only other additions to this system will be a 10 watt SSPA if I can get it working!