[Milsurplus] ARC-5/SCR-274 Receiver HV

[Brenda Gentry]

What I have observed is only a small reduction in sensitivity, but 
reduced dynamic range and AVC action. Strong stations are more likely to 
overload the receiver and cause audio distortion, and intermodulation 
can increase too. Audio output power will decrease, but is usually not a 
problem with headphones. I observed these when experimenting with 90 
volts plate voltage on a BC-348. 20 volts into an unmodified BC-348 with 
the dynamotor power supply reduced sensitivity slightly but audio power 
dropped considerably for a speaker. Headphone audio was still pretty 
good. I also experimented with 80 volts instead of 130 in a Collins 
75S-1 receiver, with comparable results. The audio power out for a 
speaker was noticeably reduced.

    B. Gentry, KA2IVY

On 9/7/25 10:23 AM, Ken Kinderman wrote:
> Has anyone had experince with receiver HV lower than the nominal 235 
> VDC dynamotor output? I like to run everything at or slighly below 
> ratings. Not interested in squeezing out every last watt from the 
> transmitters, etc.
>
> So except for the times I am using the dynamotors, I run the receivers 
> in the test jig and out of the racks at about 175VDC, transmitters at 
> about 540VDC. (By the way, even 175VDC is enough to blow the .05's, so 
> I am on a long term quest to replace all, either with re-stuffed cans 
> or just wiring them in. Otherwise, letting them fail is like playing 
> condenser Whack-a-Mole)
>
> My question is about the receivers... aside from maybe the 12A6, are 
> there any downsides to lower overall plate voltage?
>
> Thanks
>
> Ken
> W2EWL
>
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