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

[Garey Barrell]

Jim -

Looks like the meter scale on the 51J-4.  On the J-4 at least, the 0-100 
dB scale indicates "dB above AVC threshold".  So an "S-9" signal is 40dB 
above the AVC threshold.

Rod Blocksome's 75A-4 survey in 2000 didn't address this type of meter 
scale, only the dark and light red bar above S-9.

It's all relative anyway!  :-)

73, Garey - K4OAH
Atlanta

Drake 2-B, 4-B & C-Line Service CDs
<www.k4oah.com>



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
>
>
>
>