Gregg,
I don't know why the ratio was changed in the first place, but I really
don't think it will make much difference in the signal level. You can try
re-winding it and see what happens. The biggest difference should be in the
termination impedance of the filter.
The 20/5 transformer has a turns ratio of 4 which is an impedance step-up of
16; while the 11/3 is a 3.67 turns ratio or an impedance ratio of 13.44, so
do compare the before/after CW filter passband ripple at wide filter
settings - where I would expect the major difference to be seen.
If you do try the new winding ratio, please let us know the before/after
results if you can quantify it with a fixed signal input level.
As an aside - if the KNB2 is installed, check to see if the -5 dB pad was
removed (R88 and R90 not installed and R89 replaced with a jumper.
73,
Don W3FPR
----- Original Message -----
I'm working on a Rev A board and noticed that on the coupling transformer to
the IF amp that it is built different than the Rev B models.
On this one the Red (3/4) windings are 11 and the Green (1/2) windings are 3
On the Rev B the Red (3/4) windings are 20 and the Green (1/2) windings are
5.
My question is now that I've made all the upgrades to Rev B and am having
problems in this area of the circuit (ie: low sensitivity and all the
stages prior are working properly), should I rebuild this torroid??
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