10
Nov
12

The Softrock signal generator project, part 2

After receiving the BN-43-2402 binocular cores from Kits and Parts, I was able to add the T1 and T2 bifiler wound transformers.  I then chose to do the Band 3 inductors L10-L12 since they required the least effort to wind and install in order to test the end-to-end signal path. Lastly, I added a 51Ω 1/4 watt resistor between the junction of pins 7 and 9 on U9, and pin 9 on U6 – the only significant change to the stock design of the RX II in order for the divided output of the Si570 to flow into the ABPF section in reverse. In other words, having the signal flow out of the Ensemble RX II instead of flowing into it as a receiver.

The results were as good as I expected. From 16 MHz to 40 MHz, I measured a roughly -3db response out up to zero db and then back down again to -3db in the RMS output that peaked around 4.7 volts. The sine output appears clean on the scope, but I’d like to get it measured on a Spectrum Analyzer if I can hook up with another local Ham that has one. Lastly, I did the A and B calibrations using the CFGSR tool and was easily able to set the output to agree with my frequency counter to 5 digits after the decimal point, or 10 Hz resolution.

Next I’ll be building out the rest of the ABPF band sections to see the full response from 3 MHz up.

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