My old 23cm transverter description

There is the short description of my old 23cm transverter :

I am using home built transverter of my own construction, the transverter is was designed as modular construction and divided on four main modules:

1. Receiver module

2. Transmitter module

3. Local Oscillator (PLL) module

4. OCXO 10MHz – reference clock module

1. Recever

The receiver schematic you can see on my Download page

From beginning RX module was designed as RF part of Sound Card based SDR, i.e. direct conversion of 1296Mhz signal to I/Q audio IF and further processing on Personal Computer SDR software. But in reality it was hard to struggle against Local Oscillator leakage and phase noise, so I decided to leave this idea and to use it as 1296Mhz/28Mhz converter. So now two I and Q channel are adding together, after simple 28Mhz RF phase shifting RC network, this gives additional attenuation of image channel (the main filtering is done in input 1296Mhz helical filter).

Second issue with this RX design it is – input LNA it is exact copy of input stage of DB6NT transverter. Because I was unlucky to get from this LNA noise figure better than 3dB, plus poor stability (existence of higher band microwave oscillations)  , decided to change both amplifiers stages and now I am using there ATF51343 as input amplifier and GALI39 as second stage amplifier. It give me no oscillation and NF=1.5dB, that is good enough for system that using additional LNA on the antenna feed. Please, pay attention, the RX module schematic, that is located in Download area, contains only old LNA design. I need some time, to prepare electronic copy of my, hand written, changes to schematic 🙂

23cm Transmitter

2. Transmitter

The transmitter schematic is located also on my Download page

Similar story like in RX part, but working in opposite direction:-) It had poor signal as zero IF (Audio) to 1296MHz conversion transmitter, but working nice as 28MHz/1296Mhz Up converter. Simple phase shifting RC network (it splits 28MHz signal going from transceiver to two 90 degrees shifted I/Q channels) has been  added to suppress image channel.

The Transmitter board contains also embedded microcontroller that is controlling next parameters:

  • Local Oscillator Frequency
  • TX mixer DC balance (using serial DAC)
  • RX-TX switching sequencer (to protect LNA from transmitted signal)

Transmitter PCB is stacked together with Local Oscillator (PLL) PCB.


Transmitter and Local Oscillator (PLL) + (Phase shift network) staked together