DL5NEG - A programmable 2.3-2.4 GHz to 144MHz RX converter

A programmable 13cm to 2m RX converter

There are a lot of 13cm RX converter concepts. Most of them use a multiplied crystal oscillator to generate the necessary LO signal at 2176 MHz. I have also seen a few that muliply the crystal frequency using a phase locked loop with a fixed divider. The first solution has extremly low phase noise while the second solution does not need several filters to filter out the wanted signal. Both have the disadvantage that they can only downconvert a small frequency range to the 2 meter band.

Using a VCO and a standard programmable PLL Synthesizer it is possible to generate different LO frequencys to downconvert every frequency within the 13cm band. The PLL can be programmed with a PC via the LPT1 port. Since there is a backup battery connected to the PLL the programmed bits are stored in the PLL even if the supply voltage is disconnected for a longer period. (Forget about replacing the battery, the PLL draws only 10uA in sleep mode).

Have a look a some photos first:

If you want to know how it works, have a look at the circuit diagrams.