| This
modification allows the use of
two filters. Either one or two
filters in cascade may be
selected. I wanted to improve the
CW selectivity of Yaesu FT-920
and decided to go with OEM 500Hz
and 250 Hz Inrad CW filter
combination. Installation
of Inrad kit was quite simple and
it took about two hours for me to
get the job done. Modification
kit from Inrad arrived with
detailed instructions including
photos.
More information
about this mod you can find on International
Radio web site.
I also decided to
make the "mysterious"
cap mod to the radio that should
reduce the CW blow-by. The mod
includes soldering two 0.1uF
block capacitors under the radio's
main board in filter circuit and
removal of Molex connector pins.
I do not recommend doing this
without proper tools.
NOTE: the cap
mod is not part of the
standard Inrad filter
modification!
Results:
I prepared a
small mp3 recording of CW audio
on Yaesu FT-920 after the Inrad
mod (download below). The
recording is 18 seconds long.
First part is
without CW filtering, second part
with just 500 OEM CW filter
in-line, and the last part is
with 500/250 Hz filter cascade
engaged. I edited the recording
with short burst (450 Hz) tone
between each filter sequence.
The recording was
made on 40 meters band, with
IPO-On, DSP filter-Off and
AGC-Fast.
|
