[ARC5] CW/MCW

[Richard Knoppow]

-----Original Message-----
>From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
>Sent: Nov 11, 2013 12:07 PM
>To: Geoff <geoffrey at jeremy.mv.com>, Roy Morgan <k1lky68 at gmail.com>, "tom at telmore.com" <tom at telmore.com>, ARC-5 List <arc5 at mailman.qth.net>
>Subject: Re: [ARC5] CW/MCW
>
>  I recall now, instead of "Distance" the term was "Range" on the switch.
>I need to find one and double check. They are very sharp audio filters. 
>Don't know what was inside, my filter was potted. But I do know it was
>a passive LC ckt. 
>73
>Bill wa4lav
>
     The filter people are thinking of was used with aircraft radio range stations.  These had a system of crossed figure eight antennas such that the carrier was sent to both but one was modulated with an N signal and the other an A signal.  When the aircraft was "on the beam" it received a constant tone. Many of these stations also had provisions for voice modulation.  The filter had a switch which set it for either a sharp passband at 1020 hz for the navigating tone or a sharp band stop at the same frequency for voice.  Most of these filters were designed to go in the line with headphones.  The 1020 hz pass filter worked well for CW on receivers that had no sharp IF filter.  Of course they could no nothing for an audio image. 
     MCW was used mostly because it resulted in simpler receivers.  MCW was used for marine distress work because many ships had crystal emergency receivers which could not respond to CW.  Also some auto-alarms responded only to the tone.  In general MCW is inferior to CW needing more power for equivalent signal to noise.