Soft Rock - V7 Pre Alpha

Soft Rock 7 Pre Alpha

This data is from my Soft Rock V7 pre Alpha board built using OPA227 op amps. I also had to change the phase shift capacitor (C9) to 8pf to get good IQ phase relationship. With the 22pF shown on the schematic, no image nulling was not possible. I replaced the 22pF capacitor with a 0.100 header and got fairly good IQ phase on the scope with an 8 pF cap. With this cap I can null a -50 dbm input signal image into the nosie with phase=21 and gain-3. These are pretty minor IQ adjustments, so for my setup 8pf seems to get pretty good IQ phase.

MDS was measured as -102 dbm which I do not think was as good as VK6APH measured. The specturm display does show some spurs, so perhpas perhaps I have some more work to do on this board. I did notice that looking at the IQ output on the scope, I did not see extremely sharp traces, so I wonder if there's not a little bit of oscillation or jitter going on somehwere in the switch clocking.

Some other measrements:

Input current: 30.5 ma @ 13.8 V supply
Max input signal without distortion on IQ output: -17 dbm (measured for an input signal @ 28.065 MHz)
Ouput IQ signal for Max Input signal above: 2.75 Vpp.
Oscillator Frequency: 28.053 MHz

Panadapter view, SR 7 attached, no RF input

Panadapter view, Nothing connected to Delta 44

Some pictures of the board

Top Side

Bottom Side

Comments to: Bill Tracey (

Last Updated 19 March 2006

Copyright © Bill Tracey 2006