10GHz TRANSVERTER

Front view

Front view of the die cast enclosure.

My 10GHz transverter is built around VK3XDK’s kit consisting of one multiplier board and one transverter board. The multiplier board accepts a 1656MHz input signal which multiplies it up to the X band. In order to produce this signal I designed a small board utilizing the SI4133 (this RF synthesizer chip seems rather popular among hams, VK3XDK offers one such board). This solution, apart from the fact that you can skip a couple of multiplier boards (if you use a crystal in the 100MHZ range), has the capability of using an external GPSDO as an external super-stable and accurate reference. With the transverter locked into such a reference even narrow-band digital modes can be used. It also has the added benefit that if both stations are GPS locked the transmit frequency variable is thrown out of the equation, with the other remaining variable being the antenna aiming. This fact greatly reduces search time (at a windy and cold/hot summit swiftness is of paramount importance!) and avoids the possibility of failing to find the DX station because not all variables are in the sweet spot at the same time.

Another problem in need of a solution was that somehow the transverter’s TX and RX paths must be switched between receive and transmit because normal radios have only one antenna connector (I use a FT-817 and my homebrew SDR as IF radios). As a solution I constructed a small board which achieves this using PIN diodes.A  MAR-6 MMIC was also thrown into the RX path so as to increase the transverter’s overall conversion gain (I felt it needed some extra dBs so as to minimize the FT-817’s noise figure impact in the overall noise figure of the system).

In the transverter’s business end (10GHz) a  coaxial relay does the switching between TX/RX made by HP (It is spec’d up to 4GHz but seems to work fine at least up to X band). UT-141 semi rigid coaxial cable is used for the microwave connections and RG-403 for the IF section.

The final need was for a sequencer board to orchestrate all the switching events. Built around an AVR ATtiny44 microcontroller it is designed to take advantage of the TX inhibit pin in the FT-817’s  ACC connector. This effectively acts as a PTT input to the 817. The 12V voltage output from the 817 is also monitored and in the absence of it the transverter goes into ‘safe mode’.

There is also internal provision for a higher power linear amplifier to be put in the future.

Connections end

Connections end. From left to right: 8 pin mini-DIN connector for control signals to the IF radio. IF and external reference (10MHz) BNC connectors. +12V power connector. Status LEDS.

Status LEDS

Status LEDS. A solid READY LED indicates control signals between radio and transverter are OK, blinking indicates an unconnected status. TX LED turns on when in transmit. A solid LOCK LED indicates that the internal RF synthesizer is locked to the external reference, if it is blinking its not locked.

Internal view

Internal view. Left is the HP 8765A coaxial relay. In the middle are the two VK3XDK transverter boards one on top of the other. The board on the right is essentially a 3-in-1 board, consisting of the sequencer (top), the RF synthesizer (middle) and the IF switching (bottom). The free space on top of the enclosure is for a future linear amplifier.

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