But first . . .
My first 23cm transverter, bought at the Scottish VHF Convention in 1980 was the well known MMT1296 from Microwave Modules. It cost just under £200, which in 1980, was a serious sum of money. The thing was, and this is what attracted me to it at the time; there was nothing like it on the market. If you wanted to get onto 23cm, you had to build it yourself . . . and it was British. It was an all-bipolar design too; GaAsFETs were then still too expensive. The receive sensitivity and noise figure was adequate at best and the power output was a cool 0.5W. All this was crammed into two die-cast boxes, each the size of a then standard Microwave Modules transverter. I threw together a corner-reflector and dipole and managed a QSO across Edinburgh with Brian GM8BJF. My first microwave contact!
The ‘heady’ 0.5W was increased to 7W using six 2N5944 UHF transistors! This was a design published in DUBUS and employed 2 in parallel driving 4 in parallel. Real microwave transistors were still not within my budget. I could now manage the occasional QSO on 23cm up to the Aberdeen area . Then in 1989, I managed to work Karl SM6HYG!
In 1996 I embarked on a 13cm transverter based on DB6NT's article published in DUBUS. It was when sourcing the components for this that I decided to have a go at Michael's tiny 23cm transverter that had been published in DUBUS 4/92. My version of the DB6NT MK1 23cm transverter varied from that published, in that I used a Mini-Circuits SAM-5 Mixer as opposed to the hard to find Synergy one. To date, this tiny transverter has given me years of trouble-free operation as the heart of my 23cm station. It's MGF1302 front-end is not as sensitive and certainly nowhere near as quiet as today's HEMTs but back in 1992 it was more or less state-of-the-art.
In 2004, Kuhne Electronic eventually upgraded this little beauty and made it available in the shape of the MKU13G2 with an improved front-end employing an NE32584 and completely solid-state IF switching whilst retaining the Mitsubishi M67715 RF PA.
Then, in May this year (2009) the MKU13G2B was released as a kit and I decided it was time to upgrade! Functionally the G2B is identical to its predecessor. However, the most noticeable difference between the two is in the PA circuit where the INA10386 is replaced with the newer ERA-3 from Mini-Circuits and the M67715 has been replaced with a pair of monolithic gain blocks: a GALI-4 by Mini-Circuits driving an AH102A by Watkins-Johnson. The output power is now only 400mW as opposed to 1.2W. (This reduced power output may be a minor inconvenience to some). In the receive chain, the front-end is now an MGF4918D HEMT and the INA03184 MMIC has been replaced with an ERA-8. The mixer remains the same Mini-Circuits type ADE-5. On the IF switching side, one of the BAR64-03W PIN-diodes has been changed to an HSMP-3380, presumably to accommodate higher RF drive levels (up to 3W now as opposed to 1W.) Changes have also been made to the DC switching circuitry which now includes built-in sequencing . . . a nice touch!
I think this is still the world's smallest 23cm transverter (and has been since 1992!) . . . and interestingly enough it costs less than my MMT1296 did back in 1980. OK, you have to build it yourself, but that's where the fun is.
I should point out that between the G2 and the G2B, Kuhne released the G3 which has a built in PLL for locking to an external 10MHz source. The G3 is not however, available as a kit.