[ARC5] Altitude Adjustments

[WA5CAB at cs.com]

Yes.  I was just discussing off-list the fact that the AN/ARC-3/36/49 has 
altitude compensation at 15,000 and 25,000 feet in the microphone amplifier, 
as the same sort of thing happens to transmit audio. 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 07/16/2017 16:16:36 PM Central Daylight Time, 
aaf-radio-1 at aafradio.org writes: 
> There was another altitude adjustment that doesn't get much notice, and 
> that was with the interphone systems used in multi-place aircraft that were 
> not pressurized, which was basically all of them for WWII except the B-29.  
> The reason wasn't due to HV arcing, but to compensate for the decreased 
> density of the transmission medium (air) between the reproducer (phone 
> diaphragm) and the ear drum.  Beginning with the AN/AIC-2, there was a four 
> position local amplifier switch, (as well as an optional remote switch), to 
> raise the volume level of the amplifier for every 10,000 feet in altitude.  
> Beginning with the AN/AIC-2A, this increase was handled by a pressure switch 
> that didn't need the radio operator to worry about it.
> 
>  - Mike  KC4TOS
> 
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