Mark Johnsen

Hello all...
I've recently acquired a v3 uBITX with a K1BQT agc board and running TSW v2.02 software.  How can I decrease the receiver recovery time after I stop sending cw?
Presently it is approximately 3 seconds until I hear signals.
Tnx,
Mark NB1U

Ashhar Farhan

this seems to be an agc issue. probably the timing cap needs to be reduced.
- f

On Fri, Oct 25, 2019 at 6:56 AM Mark Johnsen <mark.nb1u@...> wrote:
Hello all...
I've recently acquired a v3 uBITX with a K1BQT agc board and running TSW v2.02 software.  How can I decrease the receiver recovery time after I stop sending cw?
Presently it is approximately 3 seconds until I hear signals.
Tnx,
Mark NB1U

Curt

See how this agc is integrated,  and remove it to first get used to the ubitx native behavior.  its different but I easily adapt.  then see what the agc is doing, and if it varies with signal strength.

Curt

Mark Johnsen

Question regarding agc timing...

Referencing the July 2019 QST article authored by K1BQT he says that R5(680k) and C6(2.2uf) establishes the agc recovery time. A release time of approx. 1/2 second is noted.
Multiplying the 2 values gives a value close to 1.5 seconds if I performed the math correctly.
To reduce the agc time constant to published 0.5 second value should I decrease both C and R or can I reduce just one component?

Curt

Mark

I just pulled up excel to do a quick calculation.  The time constant for an RC circuit is T = 1 / (R*C).  note this is the time to reach 67% of steady state value, but gives us a feel for responsiveness.

T = 1 / (680000 * 2.2 * 1E-6) = 0.67 seconds.

Now defining when this AGC circuit sounds finished to your ears, it could be longer than 1 second.  Use it as a figure of merit to start with.

If you divide either the R or C by 2, it should settle twice as fast.  maybe select a couple values and use a SP2T to select between them.

I confess I have no clue the fast and slow AGC times of a typical rig, but you could pick a rig type and see what it lists in manufacturer's spec or a on-line review.

I do remember seeing the QST article - but I had already installed the VK3YE circuit that I am happy with.  Enjoy your experimenting.

Curt