[Collins] 75A-4 S-Meter History Question

[Dr. Gerald N. Johnson]

On Mon, 2006-09-11 at 07:41 -0400, Jim Walker wrote:
> I was wondering if there is someone who can explain to me what the
> unusual meter is on two 75A-4s recently sold on EBAY.  They are both
> closed items: SN# 5567 EBAY: 190023487461 and SN#5518 EBAY 230024162332.
> 
>  
> 
> Both receivers have an S meter that the lower scale is graduated in 0 -
> S9 and marking for 20, 40, and 60 dB over S9.  The top scales starts at
> 10 and is graduated 20, 40, 60, 80, and 100 dB.  
> 
>  
> 
> The only way I could see this scale to be of any use is if there were
> some switch to change the meter scales and reference like that on the
> SP-600.  Can anyone tell me if this is a last production run meter,
> something for the military or some other special application?  What is
> the top scale used for?
> 
>  
> 
> TNX,
> 
>  
> 
> Jim KZ5AW
> 
>  
Figuring 6 dB per S unit, if 10 is at S4, 20 at S5.6, then 40 dB matches
S9, 60 matches 20 over, 80 matches 40 over and 100 matches 60 over and
the 10-100 scale simply shows dB over threshold, the same dB units, no
need for a calibration change.

I don't see those epay s-meter pictures all that clearly to see the
alignment of the two scales.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer