I added an external DSP noise filter to my bitx40... it has
awesome AGC built-in, and can really cut back on noise without
garbling voice (as long as I don't turn it up too far).? The audio
out is also quite strong and clear - great for mobile use.?
Since people are often dumping the filters (as they're usually
built-in these days to the commercial rigs), they're available
used (and usually still working fine) for cheap, as well as still
being sold if you have that sort of income (probably not that bad
a price for most hams).
This could be another answer regarding AGC.
The only thing I miss is an external squelch circuit - I've got
the schematic for one that is based on voice characteristics, but
have too many pans in the fire so to speak, to build it and try it
out.
Bob
N4FBZ
On 2/21/19 10:03 AM, Jack Purdum via
Groups.Io wrote:
toggle quoted message
Show quoted text
The AGC issue is part apples and part oranges. Some AGC
circuits work off the volume control while others work off the
IF chain. If you're using the IF chain, chances are there's
going to be some messing around with the PCB itself. If you're
happy with an automatic volume control, working off the volume
control is less invasive to the board itself. The IF surgery
need not be too invasive, however. The JackAl board
(hamradiodesigns.com) provides both IF and audio AGC. The IF
surgery requires removing an SMD resistor and moving an
on-board cap to that resistor's position and then attaching a
cable to the old cap location. There is no audio AGC surgery,
since the board has its own 6W audio amp on board. (It
preserves the old ?BITX audio so you can compare the results.)
Anyway, you need to decide which kind of AGC you want and
be prepared to perform some minor surgery for IF AGC and
perhaps minor "wire moving" for audio AGC. Always remember
that no decision is a decision--thousands are using the ?BITX
with no AGC. Pick what makes you happy!
Jack, W8TEE
I too was hoping to find
answers to this same question. ?I have looked through
Sunil's documents and I think the question above needs
clarification. ?We are interested in how/where to connect
the plugs/wires from the AGC kit to the Bitx40 board.
?Some other models show Bitx20 boards having circuit oard
traces cut and pins soldered in to "receive" the plugs
from the AGC board. ?In bringing this AGC board tothe
Bitx40, one does not want to cut or modify the board
without some awareness that the process is correct. ?Other
AGC circuits call for removing wire(s) from the volume pot
for audio "in" then runing "out" from the AGC boardack to
thevolume pot. ?Again, that is for a different circuit,
but we recognise the wire-up could be similar. ?One just
is not interested in finding out by way of smoke, that
connections were incorrect.....many thanks for any input
to a 2 year old posting...73
