[ARC5] More ZB

[Michael A. Bittner]

One of the unique and intriguing things about the ARR-2 circuitry is its reactance controlled BFO.  A 9001 reactance tube across the BFO tank coil allows it to be controlled by a rheostat in the remote control panel.  The advantage of this is the elimination of mechanical controls and flex cables as would be needed for a variable capacitance or permeability control.  Besides its obvious advantage in an aircraft where the pilot's control is remotely located with respect to the receiver, it is even advantageous in a receiver with front-panel controls in that the BFO can be placed anywhere in the receiver with having to have a rigid or flexible shaft connected to a knob on the panel. A single wire, that carries no RF, is connected to the BFO control rheostat on the front panel and the other end of the rheostat is grounded.  It's a nifty idea and it works.  Mike, W6MAB
  ----- Original Message ----- 
  From: Mike Hanz 
  To: Robert Eleazer 
  Cc: arc5 at mailman.qth.net 
  Sent: Saturday, July 09, 2011 10:22 AM
  Subject: Re: [ARC5] More ZB


  On 7/9/2011 12:37 PM, Robert Eleazer wrote:
  > The F4U-1 Corsair pilot's manual, the one issued during the latter half of 1944 has the following info on operation of the ARR-2:
  >
  > So, with the ARR-2 even the pilot of a single seat aircraft was given the ability to switch the received ZB modulation frequency, which was changed by a set schedule as well as the sensitivity of the set.  He also could adjust the "Tone," which I assume was done with a BFO?  Except that I do not recall that the ARR-2 had a BFO, so perhaps it was purely an audio tone.

  There is a BFO in the receiver.  Beyond that, the label on the square 
  knob on the *C-2/ARR-2 and C-38/ARC-5 control boxes read "Beat Note" and 
  "Pitch" respectively, which sorta implies a BFO.

  > Finally, the manual shows a view of the radio controls in the cockpit, including a a tube mounted along the longitudal axis of the aircraft fuselage, and located just above the  radio control boxes, identified as "Navigation Antenna Control."  I have no idea what this could be.  Any ideas?

  Not without a more comprehensive description of its appearance...

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