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

[Sandy]

These were often an accessory to the "radio compass" or ADF receivers.  
Many times a "range station" would send out weather bulletins.  There 
was usually 3 positions:  "normal" or straight thru audio, "range" which 
just passed the 1020 hz tones and "voice" which notched out the 1020 
tone allowing the weather voice information to come thru minus the 
annoying tone.

The "radio ranges" were fun to fly and practice on during clear weather 
and get a pilot used to relying on "riding the beams" so he learned to 
trust them in a low or "no visibility" condition when there were no 
visual aids or other radio aids to help you get lined up on a runway!  
It was crude but it worked.  Didn't require anything but a headset and a 
working compass.

VOR made the old range stations obsolete and they gradually completely 
disappeared.  GPS has made a lot of the older aeronautical aids 
outmoded.  Now it is rare to find an airplane which has an ADF 
receiver.  Back during the "pre-VHF" radio sets era, the common thing 
was to tune in the tower on the LF band (200-400 khz) and transmit to 
the tower on the old 3105 Khz (later 3023.5 khz) aircraft hf frequency.  
6210 was also commonly used as a backup or alternate air to ground 
channel.  It was crude but it worked.  After WW2 VHF band pretty much 
took over the
job and the HF and LF stuff faded away into the past.

73 to all,

Sandy W5TVW

On 4/26/2016 12:06 PM, Michael Bittner wrote:
> While we are on the subject of range/beam filters, I am still looking 
> for a schematic diagram and/or wiring diagram for my F-90/AIC 
> range/beam filter.
> Scott W7SVJ confirmed that its input and output impedances are 150 
> Ohms, and Mike Hanz provided information on its use in the 
> Intercommunication Set AN/AIC-8.  However, its correct hookup and 
> internal circuitry remain an enigma.
> BTW, 1020 Hz is the 17th harmonic of 60 Hz.  Back in the day, the 
> power line was used as a readily available frequency standard.
> Mike, W6MAB
> --
>
>     ----- Original Message -----
>     *From:* DSP3 <mailto:jeepp at comcast.net>
>     *To:* arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>
>     *Sent:* Tuesday, April 26, 2016 8:20 AM
>     *Subject:* Re: [ARC5] What is a "radio range filter"?
>
>     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
>
>
>
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