Thursday, January 13, 2011

NE612 Transverter

Something I found on the internet and would like to share:
I have seen NE612 transverters before, those were using two NE612s. JA6HIC uses one chip for both RX and TX conversion. The rest of the design involves an external LO.

The circuit is fed by RX and TX control voltages, this may be handy in places, although I believe that this is merely a remainder of JA6HIC's earlier designs involving diode mixers.
However, I believe a running the transverter from the general supply could be advantageous in particular since there could be a delay between powering down the RX and powering up the TX trains, which could cause the circuit not being supplied and therefore shut down. Using an external LO, it would not matter to shut down the transverter for a moment. However, the NE612 has got an internal oscillator, when using this, we certainly would not like to power down the chip just to power it up again... this would result in terrible chirp.

So, this is my plan: make use of this very simple but elegant design for transverters for 136kHz, 501kHz and 70MHz.  I will be using the internal oscillator of the NE612 as a crystal oscillator. The following obvious options will be available cheaply (the mark (-) indicated subtractive mixing which inverts the band, (*) indicates my preference):
  • 136kHz: 2.000MHz - 160m band (-)
  • 136kHz: 2.048MHz - 160m band (-)
  • 136kHz: 3.500MHz - 80m band
  • 136kHz: 3.579MHz - 80m band
  • 136kHz: 3.686MHz - 80m band (-)
  • 136kHz: 7.000MHz - 40m band
  • 136kHz: 7.159MHz - 40m band (-)
  • 136kHz: 10.000MHz - 30m band (*)
  • 136kHz: 14.000MHz - 20m band
  • 136kHz: 14.318MHz - 20m band (-)
  • 136kHz: 27.000MHz - 11m band 
  • 501kHz: 2.458MHz - 160m band (-)
  • 501kHz: 3.000MHz - 80m band (*)
  • 501kHz: 3.072MHz - 80m band
  • 501kHz: 3.276MHz - 80m band
  • 501kHz: 4.096MHz - 80m band (-)
  • 501kHz: 4.194MHz - 80m band (-)
  • 501kHz: 6.5536MHz - 40m band 
  • 501kHz: 13.560MHz - 20m band 
  • 501kHz: 14.745MHz - 20m band (-)
  • 70.0MHz: 20.000MHz - 6m band (*)
All there is to do is to build an RF-vox circuit and an attenuator (for the TX).