Sorry guys,
On the TX side it is R23/43 on RX side is R13/33. It worked as AGC for RX
and ALC on TX.
On RX I controlled the gain from received audio on TX was a DC gain
control pot.
I can't provide specific circuit details from here as I am holed up at
the farm. All these
experiments were done on a bitxv3 board. To experiment with this idea you
will need
to be knowledgeable on the subject and not for beginners.
Raj
At 28/10/2020, you wrote:
toggle quoted message
Show quoted text
Loris is right, Raj's R23 and
R43 are both on the transmit side of the uBitx bidi amps.
So perhaps not AGC for the receiver, which is what most would be
interested in.
But could also work on the receive side of the bidi amps.
A clear and complete description from Raj would help others to try it,
"introduce a varicap" is not terribly specific.
A search in the forum posts for "Raj AGC" finds no hits on this
AGC scheme.
Don, ND6T, had a couple blog posts about easy hacks to implement manual
RF gain
on the Bitx40, should be possible to make these work on the uBitx.
Dozens of threads in the forum on adding AGC to the Bitx40 and
uBitx.
The "automatic" part of AGC may not be needed, but a simple RF
gain control
to avoid receiver overload would be good.
That and back-to-back diodes in the audio chain somewhere
to prevent blown eardrums when using headphones.
Jerry, KE7ER
On Wed, Oct 28, 2020 at 06:10 AM, IW4AJR Loris wrote:
- On Wed, Oct 28, 2020 at 12:31 PM, Raj vu2zap wrote:
- I had experimented with a AGC which was very simple. Disconnect R23
and R43 from ground and introduce
- a varicap which I had MV2109. A series resistor to the varicap
through which you varied the capacitance
- and thereby the gain. This method worked very well with both IF
stages and even on the TX branch.
- I wish some members would experiment on this approach.
- Hello Raj ...
- Interesting solution, if I have some free time I could try it!
- I would like to have an explanation from you:
- what is the function of AGC? transmission for uBITX? ... perhaps
as a compressor instead of an external speech-processor?
- Thank you, 73 Loris - IW4AJR
Raj vu2zap