[ARC5] CW/MCW

[Geoff]

Feeding the BFO into the last IF allowed increased injection level and AVC 
could also be used.  That was around in the 30's

Good stability was not.

Carl


----- Original Message ----- 
From: "Fuqua, Bill L" <wlfuqu00 at uky.edu>
To: "Roy Morgan" <k1lky68 at gmail.com>; <tom at telmore.com>; "ARC-5 List" 
<arc5 at mailman.qth.net>
Sent: Monday, November 11, 2013 1:27 PM
Subject: Re: [ARC5] CW/MCW


>  It really had not occurred to me before but one possible reason is that 
> since radios of the day did not have product detectors.
> Receiving CW required turning off the AVC, turning up the volume control 
> and constantly changing the RF/IF gain for a suitable
> audio level. With out AVC you could not just leave the radio unattended 
> monitoring for a CW signal, especially for a beacon.
>  I just don't understand why they did not begin using a product detector 
> earlier except that possibly they were concerned that
> the BFO would leak into the earlier stages of IF and desense the receiver.
>  I have a HQ129X that I got years ago. I have several. Actually my first 
> Novice station had one. Anyway this one had an additional
> switch added to it for a solid state (dual gate mosfet) product detector. 
> It was tied to the original BFO and works great as does
> the AGC. No leakage problems at all.
>
> 73
> Bill wa4lav
>
> ________________________________________
> From: arc5-bounces at mailman.qth.net [arc5-bounces at mailman.qth.net] on 
> behalf of Roy Morgan [k1lky68 at gmail.com]
> Sent: Monday, November 11, 2013 12:56 PM
> To: tom at telmore.com; ARC-5 List
> Subject: Re: [ARC5] CW/MCW
>
> On Nov 11, 2013, at 12:39 PM, tom at telmore.com wrote:
>
>>
>> Seeing this talk off BFO's and CW/MCW I have often wondered what is the 
>> real advantage of using MCW other than if your receiver lacks a BFO 
>> control?
>
> Tom,
>
> One reason is that WW-II radios often had modest tuning capability, no 
> CW-useful crystal filters, moderate bandwidth, and not so good stability. 
> So with all those factors, the MCW signal was easier to tune in and copy, 
> and if any drift happened in either the transmitter or receiver, the 
> signal would not be lost so easily,
>
> In the case of radio navigation beacons, the receivers were homing on the 
> signal with a loop and sense antenna using the steady carrier. The ID 
> signals were AM modulated on the carrier and could be copied while the 
> radio was in its normal mode.  A lot of trouble for the pilot can be 
> avoided if you can both get the bearing and confirm you are tuned to the 
> right beacon.
>
> Roy
>
> Roy Morgan
> RoyMorgan at alum.mit.edu
> K1LKY Since 1958
>
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