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New RF AGC modification #ubitx

Don, ND6T
 

I have a new, more effective RF Automatic Gain Control modification. Only 0.6 dB insertion loss 1-30 MHz below S9, and up to 50 dB @3.5 MHz, 34 @30 MHz, dynamic range. Fairly simple design and less than 2 ma. current drain. I have the project posted on ND6T.com
73, Don

AA7GW
 

Is there an error on the drawing showing the RF AGC PCB mounted to the Gain Potentiometer, or is there an error in the Farhan schematic?  Looks like K1 and K3 are reversed at one place or another?

Don, ND6T
 

Indeed there was. Thank You!
The new graphic sketch had the relay labels reversed from Rx to Antenna. Schematic and text were correct, as were the graphics in the RF Gain pages. I just got turned around and TOTALLY missed it. All is corrected now. I hope. Good eye!
73,
Don

KE6BB
 

Don,

I think there is an error in the text as well:

"Run a jumper from the wiper lug of the gain control and connect to the vacant pad of C3."
It appears that should say, "...to the vacant pad of C1."  Also, the schematic calls for the audio to feed from the volume control high side, where as the above statement suggests using the wiper.  Not a big deal.  If one way doesn't work iI'l try the other.

Thanks,
Mark,
KE6BB

Don, ND6T
 

Hi Mark,

No,  the text is correct. The paragraph is relating to the RF Gain control, not the volume control. We don't touch the wiper of the volume control. The wiper of the RF Gain control is connected to the RF input of the AGC attenuator array through C3. That is properly shown in the drawing (the blue wire) and on the schematic.

The graphics staph does not get paid this month due to their regrettable errors but the editorial staph gets their usual salary. This time.

Thanks Mark. Keeps me sharp. I may re-word that and will try to be clearer in the future.
73,
Don 

KE6BB
 

Thanks, Don.  That clarified it.
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Mark,
KE6BB

Mike
 

Hi. Is there an error in the wiring instructions of the coaxes here? -> http://www.nd6t.com/uBITX/Graphics/potmnt2.jpg

Shouldn't it be to K3 pin 3 and not pin 14?

(In the schematic on hfsignals.com pin 14 look like is ground?) http://www.hfsignals.com/wp-content/uploads/2017/12/ubitxr4.pdf

73

Don, ND6T
 

Well, looky there! Mike, I hadn't noticed  but it looks like Farhan moved the wiring from version 3 (the one that I have) to the other set of relay contacts on version 4 (the one that I am waiting for)! Good catch! As soon as I get my new boards I'll check that out and update the web site. I can hardly wait to see what else has changed. Just might have some more work to do. Hold off a bit, if you could. As soon as I get my new  board I will get right to it. Thank you.

RCBoatGuy
 

Relay K3 has different pin assignments in the r4 schematic compared to prior versions. 

The AGC mod was created before the r4 schematic was released. 

73,

Carl, K0MWC