[ARC5] What is a "radio range filter"?

[WA5CAB at cs.com]

Further to what everyone else has written, the Signal Corps fielded several 
Range Filters all tuned for 1020 CPS.  The FL-5 and FL-8 are Hi-Z (around 
4K ohms) and worked with the original SCR-274-N sets plus any other early AAF 
receiver that tuned below the BCB,  The FL-8 has the selector switch 
mounted on it and has phone jacks.  FL-5 is the same filter in a smaller box.  It 
used the BC-345 remote switch and the phone jacks were remote as well.

FL-30 and the later sharper FL-90 are Lo-Z equivalents to FL-8.  If there 
was a Lo-Z equivalent to FL-5, I don't have the nomenclature.

The black box with the sloping panel previously described is probably a 
NAF-68304, which is the Navy equivalent to the FL-30.  AFAIK, NAVAER never used 
an equivalent to the FL-8.  All of the Navy aircraft receivers I know of 
(at least from the RU on) are Lo-Z, although they called it 500 ohms.

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

In a message dated 04/26/2016 07:55:58 AM Central Daylight Time, 
arc5 at mailman.qth.net writes: 
> I was reading the audio operation description on the SCR-274 manual pdf 
> page 28, document page 16 . There, near the end of the first paragraph it 
> say that for single place airplane, the "pilots headphone is plugged into 
> Tel-A though a radio range filter, if used". No nomenclature given!  What is 
> it and what what it's purpose?
> 
> 
> I have heard that here was some kind of passive tone filter they used to 
> use to narrow the audio response, but I have never seen such a device. 
> Anybody know about it?
> I was wondering if it might serve as a cw filter.
> 
> 
> 
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