Wednesday, December 5, 2012

24 GHz transverter update

As I received a few queries regarding the transverter here is the update on done so far. I make some small modifications but nothing that is diverting from the original idea. I did have a big problems with the YIG PLL oscillator MTS1500 which was not working properly. I discovered that the YIG inside the whole unit is faulty, can not be locked neither controlled properly. After so many time devoted to this unit I quit and order the other YIG PLL oscillator DFS-1201 which is working as required, immediately after first start. More over I program two frequencies so the same unit can be used aloso as the LO for the 47GHz operation.

Briefly, here we have a DFS-1201 YIG PLL programmed for L.O./2 frequency to suit the 436MHz IF. DFS-1201 is controlled via the small PCB with the PIC microcontroler (directly on the DFS-1201 connector) where 2 programmed frequencies are available. The output signal is 14dBm and splited in two for upconverter and downconverter. No waveguide relay as mentioned previously, isolator is good enough to protect the downconverter from the 300mW which can produce the TRW upconverter.
The bottom PCB is switching the voltages for the units and acting as a small sequencer together with the IF attenuator and switching.
Power supply boards with the voltage stabilisers are attached to the left/right walls of the plastic housing.

The antenna is attached directly to the third isolator port through the short peace of the WR-42 flexible waveguide. The antenna is not so big and the radom has been dismantled to make this system light and easy for operating. Even not so big the antenna is quite sharp and careful pointing is required.

Some initial test were performed and overall feeling is that the transverter perform very good. The RX NF is very good and the YIG PLL stability after initial warming up of 5 minutes is excellent. Circulator instead of  relay seems to be a very handy because no headache and fear to burn the downconverter front end. No "smart" sequencing is required and loss are reduced to the minimum.
Present ODX is 168.5 km LOS qso during the summer with the humidity close to 90% over the sea path. Winter should be the right time to gain this distance.

73 and CU on 24GHz