SR 6m/2m Converter

Posted on Feb 6, 2014

This kit, designed by Jan G0BBL and implemented and distributed by Tony KB9YIG, is a plug-in board for the Softrock Lite + Xtall RX V9. 0 which down-converts VHF signals in the 2m and 6m bands to HF signals that can be received on the V9. 0 RX. Also documented here is a 4m version (four metres, for our EU friends), courtesy of Bob G8VOI. The parts f

SR 6m/2m Converter
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or the 4m version are included in the kit, with the exception of two capacitors (2. 2 pF and 120 pF ceramic) which the builder must obtain. In addition, the schematic calls for band-specific parts C15 and L5; however, these were subsequencly dropped from the final design as unnecessary. The builder will find invaluable information at the website of Fred PE0FKO, especially the setup of the software and firmware, as documented in the excellent users manual from Bob G8VOI. The converter plugs into the Softrock Lite + Xtall V9. 0 RX at the on-board jacks J1 and J2. Power comes from the V9. 0 RX`s 12 Vdc bus (on pin 3 of J2). The down-converted VHF signals are fed to the V9. 0 RX QSD circuit via pins 7-9 of J1/P100. The incoming signal from the Antenna terminal (or, via a jumper wire from J1/P100 Pin 1), e. g. , 144MHz, is pre-amplified by Q1 and fed to a double-balanced mixer, U1. U1 also receives a Local Oscillator signal via pin 4 of V9. 0 RX`s J1. This local oscillator signal must be at a frequency (e. g. , 115. 2 MHz) which, when mixed with the incoming 144 MHz signal, will produce both a difference (144 - 115. 2 = 28. 8MHz) and the sum (144 + 115. 2MHz = 259. 2MHz). Fred PE0FKO`s Firmware handles this translation. See notes below on how to program the Local Oscillator to result in an IF frequency that is equal to the V9. 0 RX`s quadrature clock frequency. The output of the mixer at U1`s pin 2 is filtered to remove the sum...

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