Posted by
Geoffrey Mackenzie-Kennedy-2 on
Nov 17, 2004; 11:24am
URL: http://elecraft.85.s1.nabble.com/Low-voltage-on-AGC-threshold-tp371652p371660.html
Mike ,
Typing error in my post, last line. Low voltage should be 2.600 not
2.667 - same as you get. Sorry.
73,
Geoff GM4ESD
----- Original Message -----
From: "Geoffrey Mackenzie-Kennedy" <
[hidden email]>
To: "Mike, W8ENG" <
[hidden email]>
Cc: "Elecraft Discussion List" <
[hidden email]>
Sent: Wednesday, November 17, 2004 10:53 AM
Subject: Re: [Elecraft] Low voltage on AGC threshold
> Mike,
>
> There is a design problem in this circuit, IMHO, which has to do with
> tolerances, and I am having an off list discussion about it. Nothing
> serious, and I am sure that it can be fixed easily. I'm letting you know
so
> that you don't damage anything by too much poking around in K2. The 3.78
> volts that you read at U2 pin 5 is 0.053 volts higher, I figure, than you
> should get with the 7.8 volts from the 8v regulator, if the RP6 resistors
> are 5100 ohms +- zero!! Three terminal voltage regulators also have
> tolerance specs on voltage output as measured at the regulator output
> terminal, so 8.000 volts is not a sacred cow.
>
> I had exactly the same sort of problems, slightly different voltages. But
K2
> was VERY useable with AGC on, but not quite up to full sensitivity being a
> little bit "AGC limited".
>
> 73, Geoff GM4ESD
>
> PS : The low voltage that you get is 2.6 volts - I figure that you
should
> get 2.667 volts - nit pickey fussy eh?
>
>
>
> ----- Original Message -----
> From: "Mike, W8ENG" <
[hidden email]>
> To: <
[hidden email]>
> Sent: Wednesday, November 17, 2004 12:44 AM
> Subject: Re: [Elecraft] Low voltage on AGC threshold
>
>
> > This is an update to my earlier post. I touched up a solder joint and
> > reassembled the radio. The voltage on pin 5 of U2 was still 3.78 volts,
> > with the RF gain set fully clockwise. The input voltage from my pow
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