Hate to admit it but nine years passed before I found a matching audio
filter for my Ten-Tec Argo's (505 & 509). That was just a month ago!
In the interim I used MFJ's CWF-2 in various forms. The filter is a fine
performer, every bit as good as the Ten-Tec design and maybe even
a little better depending on the example.
The CWF-2 works best when wired into the audio filter input jack on the
rear of the Argo's. This places it in front of the AGC. Ade Weiss,
K8EEG/W0RSP did a complete article on this installation in an older CQ
magazine, late 70's or very early 80's! Sorry, no dates available!
Alternativly just plug the CWF-2 into the audio output. It is a little
noiser and the AGC will pump at times. And, the filter tends towards
ring in the 80 Hz position on strong signals. It's livable, however!
I routinely buy CWF-2's at hamfests for $5.00 to .50 depending. The
boards are usually glued in place but over time the joint tends to fail.
A "rattling" CWF-2 is usually good for a buck. The boards are pretty
much bulletproof so a dab of glue and a new 9V battery and the filter is
as good as new.
The secret to the CWF-2 is the matching of the capacitors. Martin Jue
shared this with the St. Louis QRP Society several years ago when we
decided to kit the filter (twice). It was a fine project for us!
I have never found a CWF-2 that did not perform exceptionally well.
The three position filter has 180, 110 and 80 hz bandwidths and the
circuit seems to amplify received signals a bit. This can be a big plus
when used with small single-band xcvrs like the NorCal40, 40-40, etc.
Hope this info is helpful to those a little short on Ten-Tec 208A's!
de Dave, NF0R nf0r@slacc.com
[
QRP-L Archive |
]
[
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000
]