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

[DSP3]

Brian has is pretty much correct.  The "range filter" was designed to 
pass 1020 Hz audio through the phone audio system of certain aircraft 
receivers when tuned to a "range station".  1020Hz became the de facto 
standard for Morse audio identifiers  of NDBs, VORs, Marker Beacon, etc. 
as well as the keyed tones for the now defunct Adcock system (the true 
range stations). Both the AAF and the Navy had their versions of the 
filter, some controlled at the filter, and some remotely switched in and 
out.  The FL-8 is one of the more//prolific models. Most current audio 
panels and Nav or NavCom sets will have a 1020 Hz filter circuit for the 
Marker Beacon channel and to selectively filter the identification audio 
from the other VOR/ILS modulations present.

Jeep - K3HVG



On 4/26/2016 9:37 AM, Brian wrote:
> As I understand it, the radio range filter is a passive, 
> narrow-pass-band filter that increases the signal-to-noise ratio over 
> a very specific band of audio frequencies, such as would be used in 
> the A-N airfield landing path guidance system. This is not the glide 
> path or slope system, but the azimuthal system. The filter is 
> contained in a cast metal case about 3” x 2” x 2” and has a large 
> operating knob on top.
> It was issued ‘after market’ and was not part of the SCR-274-N kit. I 
> have one available, if you’re interested.
> 73 de Brian, VK2GCE.
> *On* Tuesday, April 26, 2016 10:51 PM, J McVey said:
> 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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