Sunday, February 28, 2010

Q-RX - a 600m Receiver Concept

When searching the internet, I found the QTX by GW3UEP. The exciter of this transmitter uses Q4 (pin 7) of a 4060 ripple counter. Q4 is the lowest division available with the 4060, hence, an 8.0MHz ceramic resonator needs to be used to generate a 500kHz frequency. The nice thing about the 4060 is its' internal oscillator.

So, here is the concept for a 600m receiver. Use a 4060 in the way as it is shown for the QTX. Generate a 250Hz frequency with it as a LO for a subharmonic mixer.
There are two obvious options to do that:

  1. 8.0MHz ceramic resonator - Q5 (pin 5)
  2. 4.0MHz ceramic resonator - Q4 (pin 7)
For a grabber, I would even consider using a 4.000MHz crystal for increased stability. The resulting audio signal will fall into the range of 1kHz to 4kHz (5.x for inclusion of the DI2AM).

In this receiver, I intend to employ a 500kHz ceramic resonator as sideband filter, provided it can be slightly pulled up by a series capacitor.