23cm NBFM Transceiver Specifications

Single-Board NBFM Transceiver Specifications:

• Narrow Band FM (transit and receive)
• Full 23cm band coverage
• Simplex operation
• Repeater operation with user-defined TX offset (including Australian 20MHz)
• Output up to 0.7 watt (15w with optional power amp)
• NF approx. 3dB
• 4-line back-lit LCD displaying Frequency, Repeater Shift, RX/TX status, S-Meter
• Digital VFO operation in 1, 5, 25, 100, 500KHz or 1MHz steps (user selectable)
• 10 programmable memories, each with unique repeater shift and CTCSS
• Memory scan function, with pause-on-squelch
• Open-source software (MIT licence) – source code available on Github
• Add power, a microphone, speaker and antenna and you are live on 23cm FM

Other features:

• True full band coverage, and way beyond - capable of receive and transmit from below 1200MHz to beyond 1300MHz. Performance has been optimised for the 1240-1300MHz Australian amateur segment. 
   
• Rx signal strength displayed in dBm (instead of ‘S’ units). Whilst not calibrated to NATA standards you can certainly use the dBm readout to measure relative antenna performance and propagation changes etc. “I’ve changed antennas and am receiving you 3dB stronger”.
   
• Simple, almost-zero alignment. Alignment of the TX strip comprises peaking of RF power out via a single stripline short. Set the deviation level and that’s it. RX strip alignment is only slightly more complex.  

Options:

• 15W RF output – Increasing the transceiver RF output to 15W can be achieved by adding an antenna relay (e.g. minikits.com.au or W6pql.com) and 15W 1200MHz power amplifier module (available from AliExpress). The power module we have used has ~40dB gain and so requires a ~23dB attenuator at it’s input to avoid over drive. It operates at 24-28vdc which can be supplied by a cheap 12v/24v switch mode inverter (eBay or Aliexpress). No tuning or alignment of the PA is required. 
   
• RF Pre Amp – Operators in quiet areas working weak stations may benefit from the addition of a pre-amp to increase front end sensitivity. A simple preamp is in development. 
   

Detailed technical information can be downloaded from here.