Saturday, September 20, 2014

1296Mhz transverter revived

Many years ago I built a 1296Mhz transverter using the DF8QK design from VHF/UHF Communications magazine. It took me quite a while to build and setting up and aligning was very tricky. After lots of patience, I managed to get the main part of the transverter working with an output of only about 100mw. Later, I built a three stage receive pre-amp with three BFR34 transistors and also added a single transistor BFQ34 power amplifier to increase the output to around 1watt.
The whole of the transverter was enclosed in fibre glass copper clad boards and as they were all built in separate modules, I assembled them all together, with the pre-amp and P.A. mounted separately inside a box.

I built a 10 over 10 slot fed yagi as per Radio Communication handbook (P13.25) using plumbing pipe and brass rods. This together with the transverter worked well. Unfortunately, back in the early 1980's there was little activity on 1296Mhz, so I hardly heard anything! When I took my shack apart and kind of 'gave up' amateur radio the transverter has stayed in the attic. The antenna gradually fell apart.

Since I have returned to amateur radio again I have taken part in the Tuesday evening activity contests. In fact, I have operated on all the contest bands, except 1296Mhz and above. I felt a bit left out with 23cms, surely there must be activity on these nights?  Several times I have brought down my old transverter and connected it to my Yaesu FT101E, but heard nothing and have not even been sure whether the transverter even works any more. It got to the stage where I was about to throw it out because it I really couldn't be bothered trying to fix and align it all again after all the problems that I had initially.

Then earlier this year I got a SDR receiver which works happily on 1296Mhz. So on the contest nights I tried it out to see if I could hear anything on 1296Mhz. I was quite amazed to find that I could hear several stations with just my 70cm antenna connected!
On Tuesday this week I decided to try just once more to see if I could hear anything on my old transverter. I put in all the plugs and checked all the connections then switched on - nothing! I stood staring at the little beast scatching my head. Then suddenly I had a thought...I wonder if the oscillator crystal is working? I flicked the crystal a few times then with my fingers turned the core of the coil a turn.

OMG! It burst into life! I tuned and heard several stations in the contest...I was amazed! I listened for a while and wondered if the transmit part works. I found a strong station and called him...I works!!
The station I called was G4NTY/P and he came back with a 5-3 report although he was 5-9 with me.
I was so pleased that after all these years the transverter still works! I carried on working some more stations with the transverter connected to the 70cm antenna (No antenna for 1296Mhz)

My log now shows:


Not bad for a home made transverter built back in 1980!

Now I need an I build another 10 over 10 or should I splash out and buy myself a 1296Mhz Tonna?  Watch this space!

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