Friday, June 2, 2017

A New Line of Transceivers ~ DifX

Transceiver Architecture 2.19

6/4/2017 ~ The Dishal Saga continues.

Bob, N7SUR shared his Dishal experience (he was very successful) and in his configuration he has a TIA amp ahead and following the filter. He is also using a AD9850 signal source. I added a front end amplifier and the results improved somewhat. This added about 15 dB of improvement. The real test would be to add an amplifier on the back end and make another run. But NOT THERE yet but better than earlier. The theory about amplification is that the scope may not be detecting the lower signal levels (masked by noise) and with a boost this enable better readings.

73's
Pete N6QW


6/3/2017 ~ More Listening Test with New BFO Frequencies

(BTW only 1 kHz below/above the apparent Center Frequency --what does that tell you?)

 
 
 
The Dishal Filter must be on par with Fake News!
 
73's
Pete N6QW




Four weeks of work and this is what you get --not very satisfied!!!!  Several blog posts ago I mentioned about Method #1 which simply is finding 6 crystals that are no more than 50 Hertz spread among any of the crystals, use 150 PF NPO caps and build a ladder filter. Assume the Zin/out to be 150 Ohms and get on with life. I would bet that approach would have netted a much better filter. If you are considering the Dishal approach opt for Method #1.

 
 
 
 
73's
Pete N6QW