[R-390] 2 diode agc ssb mod c/l meter linearity

[Jordan Arndt]

P.S...

I used 1N4001 diodes rather than the 1N4003 diodes to rectify the AC voltage 
because they were small and on hand...

agn...73...Jordan VE6ZT


----- Original Message ----- 
From: "Jordan Arndt" <Outposter30 at shaw.ca>
To: "David Wise" <David_Wise at Phoenix.com>; "Larry H" <larry41gm at gmail.com>; 
"R-390 Forum" <r-390 at mailman.qth.net>
Sent: Friday, August 27, 2021 11:02 AM
Subject: Re: [R-390] 2 diode agc ssb mod c/l meter linearity


>
> ----- Original Message ----- 
> From: "David Wise" <David_Wise at Phoenix.com>
> To: "Larry H" <larry41gm at gmail.com>; "R-390 Forum" <r-390 at mailman.qth.net>
> Sent: Friday, August 27, 2021 9:06 AM
> Subject: Re: [R-390] 2 diode agc ssb mod c/l meter linearity
>
>
>> * An alternative to Jan Skirrow's op-amp mod, this minor IF Deck design 
>> change lets you drop in virtually any meter movement without modern 
>> technology.
>
> Just an FYI...
>
> I use a Carrier Level meter ckt similar to the Skirrow and KH6GRT op-amp 
> mods, but I use a 741 Op-amp with different component values...The small 
> PCB also mounts on the rear of the meter, but it could be made much 
> smaller and mounted elsewhere if the builder chooses to do so.
>
> The circuit is very similar to the KH6GRT ckt found here:
>
> https://www.qsl.net/kh6grt/page4/R390meters/CarrierMeterAmp.pdf
>
> The values I use are:
>
> R1 18 ohms 1/2W (what I had on hand)
> R2,R3  2700 ohms 1/4W
> R4 100K ohms 1/4
> R5 5Kohm multiturn variable
> R6 not needed
> C1,C2 25uF 16V
> C3 not needed
>
> It is very linear from 20 to 100dB on the A&M Inst. 0-100dB 1ma FS 
> calibrated meter I'm using in my 1959 Stewart Warner 390A.
>
> 73...Jordan VE6ZT
>
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