Re: RFI from uBitx TX after AGC and other mods installed

Michael Shreeve

Just starting the pop fix. Looking at your circuit and the uBITX circuit. I've enjoyed your art work BUT, I"ve never worked with art work. Occasionally a large identification pc board photo or graphic showing components locations has been available for the millions of circuit boards I've worked with over the years. But, schematic are what I usually use and I thrive with them. And before switching to communications as my specialty I would get tons of consumer grade stuff and need to draw a schematic. 

 I have a 10x17 for V3 and V4.  

What would be best for me would be a real schematic with an X where the circuit is separated (in most cases cut, nut not always, Tombstoning the caps does the same thing, freeing up the "IO" line, no cut necessary..). An "IO" would be drawn with a simple line. On the new V4 Ashhar has put a test point TP20. At least on the schematic, not sure if he had new boards made, although would be hard to put the direct coupled audio amp in the circuit without completely changing and re-doing the board. . A line would be drawn to the point "c63" ON THE SCHEMATIC with an X showing a connection that is no longer there.  Same for C50. (which can be accomplished by tombstoning)  .

 . Rx and Tx control lines seem to be self explanatory. For me, even though I like your art work, this is how I do best with circuits and circuit changes. With a true schematic featuring both the uBITX and your circuit,  I will then raise (tombstone) c=63 and c-50 the correct way. That's how I've always worked best, with an actual schematic showing the entire circuit . I may try to draw the changes in pencil and submit the graphic somewhere. But, it would be better if you did this, since its your circuit. 

Ashar, with the V4,  did something which would be harder for us to do, and what he did was insert his pop circuit (On the new schematic for V4)  in between the new direct coupled transistor audio amp, and Q70 . , a mosfet called Q74 which I'm sure you've looked at in detail, being the owner of a new V4 . Its drawn as if its a separate little board .  It relies on a timing circuit (R78, D14, and a 1uf directly on the gate of q74) to do its magic, and hopefully it does. Too bad the first V3 didn't have this simple circuit. If it works. Does It ?

I'm not using the kit,, but rather, got a bunch of nice brand new pc board material and making the pads using a Dremel with cut wheel. That's the plan. Using the three n-channel mosfet simple circuit. 

On Tue, Jun 26, 2018 at 3:48 AM, Don, ND6T via Groups.Io <nd6t_6@...> wrote:
Alan, Sorry for the relay info. I see what you are getting to now. Do you have a "pop fix" modification in place (any flavor)?
Rowland: What happens if you unplug the AGC board (everything else still connected) and transmit? Does the feedback go away? -Don

Michael Shreeve N6GRG

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