In German Funkamateur was published schematic for hf noise generator
and described metod of mesurment by using sondcard lf spectogram. I
am sorry that it is again in russian but can be easily translated. I
couldnt find similar article in english. Schematics are
understandable on its own.
--- In BITX20@..., "vdberghak" <vdberghak@z...> wrote:
Indeed measuring is knowing if the final result is in line with
the
original expectations.
As mentioned before, it can be easily done with the sound card. At
that
time, I asked for feedback (screenshots of the same method) of
measured
filters to see if my 4,9 MHz filter is about in line with the 10
MHz
version. If some members do this measurement it is possible to
compare
results and find out if it is really a 'lottery'. As I understand,
most
builders have their filter dimensioned in accordance with the
original
schematic and they all seems to work fine?
OK builders, please download the few kb program, connect your BITX
to
the sound card, measure the shape of the filter and post the
screendump!
Thanks in advance,
Chris.
Without measuring to get
good filter is more lottery than predictable result. Only in
situation that somebody can use the same type of crystals
producer
and batch results might be comparable.
