I would like to thank Steve for posting this information concerning
incorrect component values in the Paragon II audio filter circuit. Minutes
after I received this e-mail last night, I checked the IF/audio board in my
Paragon II, and while I found that R65 was the correct value, R64 was not.
The Paragon II schematic shows that R64 is supposed to be 10K (as Steve
mentions), but my audio board had a 33K. The difference in audio filter
performance when R64 is changed from 33K to 10K is striking, and the filter
is now a true asset to the CW performance of the radio.
My biggest complaint regarding the documentation for the Paragon II is that
unlike the Paragon I, the manual does not include a component-layout drawing
(at least this is the case with the Oct, 1993 manual I have). So to do
something as simple as checking these resistor values, you have to remove
the board, guess which IC is which, start counting IC pins and match the
schematic to the board. Checking all the resistor values in the audio
filter section took some time as it was necessary to flip the board over
many times to see what traces go where, and what part is tied to each trace.
Scott
N7NB
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Steve N4LQ
Sent: Sunday, 19 December, 2004 16:41
To: tentec@contesting.com
Subject: [TenTec] ParagonII Audio BP Fade Feature Mods
If you have a Paragon II and feel that the Fade - BP audio is broad and
ineffective, check the following value on the IF/AF board. This board is
located on the bottom/front RH side. You must remove the bottom shield of
course.
R65 should be a 33k according to the schematic. Mine was a 3.3K. This
incorrect value prevented the first stage of the filter from resonating near
the desired frequency while the second stage worked fine, since it had the
correct value, 33k.
Have you noticed how the audio gain seems to decrease when turning up the
fade control, even at resonance? Change R64 from 33k to 10k. This will
equalize the gain when the filter is engaged.
Once the filter is working properly, it becomes a wonderful too for
improving CW copy.
73
Steve N4LQ
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