[Boatanchors] Reverse 'S' meter - circuit for replacements ???

[Gary Schafer]

Hi Rodney,

It sounds like the meter is now in series with the plate circuit of one of the IF amplifiers.
Some receivers that had that kind of S meter had meters that had the mechanical zero on the right
side of the meter. Also some mounted a regular meter upside down to make it read left to right.

You can make a voltage divider for a reference to feed one side of the meter (and zero the meter) and
connect the other side to the plate circuit of the IF amp. The + side of the meter would go to the
plate circuit (below the IF transformer) and the negative side of the meter would go to the divider.
The divider would go from a fixed  B+ source and ground. The center of the resistors goes to the
negative side of the meter. A pot as part of the divider will zero the meter. You may need a series
resistor in the meter also to adjust the sensitivity of the meter. Or you could jockey the value of
the dividers maintaining the same ratio.

Look at some schematics of some S meter circuits. I think that the Drake 1A and 2A, 2B have circuits
like I described.

You will probably need a more sensitive meter. A 0-1ma meter would be much better.

73
Gary  K4FMX


Rodney Bunt wrote:

> Fellow BA's
>
> I have a RCA AR88D which has had the 'S' meter blanking plate "removed" and a 'S' meter fitted,
> the 'S' meter is a conventional left to right movement. The drive for the 'S' meter is such that
> strong signals reduce meter current and weak signals increas meter current so the meter reads
> backwards for signal strength.
>
> Has any on a circuit, or an internet link to a circuit, for inverting this signal, an OP amp od
> differential amp etc. with "dc offset/zero and gain controls" I could use the dial lamp supply to
> derive + and - volts for the OpAmp. Meter sensitivity is 10ma FS.
>
> PS: anyonr have the cover for the 'S' meter panel, that is also an option (put it back to
> standard!!!)
>
> Regards,
>
> Rodney
> VK2KTZ
>
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