Building a 23cm NBFM transceiver!

after I installed 2 Diamond X5000 antennas on my roof and I played a bit with my 23cm transverter from SG-Lab ( ) I wanted a dedicated 23cm FM transceiver. On E-bay there was no real offering and the Kenwood (tm741) I got from a friend unfortunately died (controller) before I could even test it ;-).

So I found the 23cm NBFM TRX project from Bas PE1JPD from Holland:

This is a really nice kit for a very good price ( €157 )and I decided to order it. Very well packaged I received the kit very quickly and Bas even added an additional PCB which takes the display, mic connector and all other switches and buttons (for mounting behind the front display) – this saves wiring.

So today (01.06.2019) I got both the receiver and transmitter working correctly and I tested succesfully on a couple of 23cm relais in the region. So the following is open:

  • tune the PA to get ~ 1W output
  • add a 1750 Hz tonegenerator
  • replace the linear pot with a log pot – DONE
  • replace the BC547 with a BS170  (and a 100k resistor) – DONE
  • Build everything into a nice case
  • Build a 23cm PA (I would like >10W output)
The kit
SMD components installed
First non-SMD components installed
Most PA components and RF-Chokes (3 windings on 5mm drill)
Nearly done!

Tips and Tricks:

  1. Dont follow the BOM from the 4.0 documentation. Build the kit from the schema – the BOM is not completely updated.
  2. When ordering this kit, also follow the AO92 update – this is the updated PLL, installs the 3,3v voltage regulater etc.

  3. From the above link, the text ” remove R29 and connect C43/R29 to +5V via a resistor of 1k. ” is wrong. Connecting the 5v through a 1k resistor drops the Vp to the PLL to approx. 4,5 volt, which prevents you to cover the whole band up to 1300mhz for transmit. With 4,5v you can only tune up to 1282mhz. So connect the 5v without the 1k resistor.
  4. The MAR-8 is hard to get, the successor is the MAR-8A which operates on a lowered voltage, 3,5v instead of 7v. If using the MAR-8A instead of MAR-8 you need to increase the values of the two bias resistors R2 and R33 from 150ohm to 270ohm.
  5. A lot of other good tips, tricks and modifications are found here:


This entry was posted in 23cm. Bookmark the permalink.