Mike's kit is a Nortel ODU modified from 23GHz which provides a complete "24GHz in a box". An internal relay requires positive volts up the the coax to switch to TX, and the unit requires 1W at 432MHz to generate 0.25W at 24,048MHz. The FT790R Mk1 is an ideal driver radio for this unit. The Nortel power supply requirements are between -36V and -48V, so a DC/DC Converter was used powered from a separate 12V leisure battery source.
On Sunday it was the first UKuG 24GHz/47GHz/76GHz Cumulative and I was eager to see if it all worked! Mike had warned me that the unit had been stored for the past 10 years and there was a frequency offset of +/- 150kc. So my plan was to test the RX first and then try and find someone local to boldly attempt a QSO with. Like all of my Microwave endeavours I was prepared for complete failure and hardship. That way anything positive is a pleasant surprise!
I need to spend some time working out how to fix the unit to a mast. But for now a small white plastic patio table was utilised to provide a flat surface on top of my surveyors tripod. This seemed to provide a useful workable solution!
First stop was Knowl Hill IO91OQ about a 10 minute drive from my home QTH. I decided to visit a site north of the A4 which is higher than an alternative site just to the south. The location is accessed from a footpath and presents a SE to S facing hill. I quickly set-up in a field of sheep. The first objective was to try and find the Reigate beacon GB3SEE (62km to the SE) to test the RX and to find the frequency offset. The transverter RX seemed to be working as there was a healthy increase in noise, and on TX a reassuring clunk of the relay! However, after significant sweeping of the band up and down, and pointing the dish to where the beacon should have exactly been on a direct path, nothing was received? This was disappointing but you have to be thick skinned for all this microwave lark, see my other blog posts about 10GHz! Whilst onsite Mike G6TRM/P in JO01QD (162km to the SE) near Dover phoned me. We tried to complete a QSO over what would have been a very marginal heavily obstructed path, but nothing was heard. We are yet to make the path go on 10GHz, so 24GHz was somewhat optimistic! However, its always worth a try.
|24GHz from Knowl Hill, looking SE|
The 2M Microwave talkback frequency 144.175MHz was busy with chatter. With just the FT-817ND and a 2m/70cm Whip antenna Keith GW3TKH/P on Blorenge (IO81LS) and Roger G8CUB/P with NeilG4LDR/P on Hackpen (IO91CL) were all loud. Martyn G3ZME/P on Brown Clee (IO82QL) was also heard looking for QSO's. So I decided to drive the 35 minutes to Christmas Common (IO91MP) about 850ft ASL on the Chiltern Ridge. After a quick "CQ Microwave Contest" on 2M I found Neil G4LDR/P who was still on Hackpen (60km to the W). We tried a couple of times on 24GHz but with no success. The Wx was hot and sunny (with no obvious humidity problems) and the views at both locations were amazing, which made up for the lack of QSO's!
|24GHz from Christmas Common, looking NW|
It was great to get back out again /P. I plan to drive down to Reigate and park up next to the GB3SEE 24,048.9600MHz beacon to work out the exact frequency offset of the Nortel unit - before the next EHF UKuG Cumulatives in June, September and October.