Re: question about crystal spacing in filter

Ruud Jongeling <pe2bs@...>


Two weeks I finished my experiment with the 9MHz crystal filter design
and reported the results of it in several files in the File-box Ladder
Crystal Filter Design. I dropped a message in the messages box about

Maybe you can start selecting the crystals the way several amateurs
suggested to you. Look at the Excel file to see how I did this for the
9 MHz filter. Selecting the filter is only the first step and doesn't
result in a good filter automaticaly. Select good C's and take care of
matching the filter to the amplifier stages is also very important.

Ashhar Farhan discribed the filter design in "A simple SSB trenceiver",
this article is in the File box. An other (but more difficult) way is
discribed by G3JIR.

What you could do is finish the BITX20 with the calculated C's. After
that you can see the shape by putting a noise source at the antenna and
send the audio to the computer. You can use SpectrumAnalyzer or an
other program to draw the shape of the filter and do some "fine
tuning" with the C's on the filter. A lot of information about this can
you find in earlier messages of this group.

Please show us the result of the filter shape after you finished the
job. Not many amateurs have done so far. Succes.



--- In BITX20@..., "eternalesquire" <eternalsquire@c...>

I never saw anything about the original article about this. I've used
the BFO and a frequency counter to measure all my crystals. How
closely do they need to be matched for SSB reception? for CW


The Eternal Squire

P.S. I am using 10.7 Mhz as the IF

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