[ARC5] Pre-ARC-5 rigs.

[Mike Everette via ARC5]

I did a lot of research for TIGHAR (The International Group for Historic Aircraft Recovery) about 12-14 years ago re Earhart's communications gear.  

TIGHAR maintains that AE carried a Western Electric 13-series transmitter, and a Western Electric receiver the nomenclature for which escapes me at the moment.  

The receiver was pretty crude.  It had no RF stage, and a 96 kc IF, having been design-optimized for reception of radio range signals (150-400 kc or thereabouts) and the AM BC band (up to 1500 kc in 1937).  It also tuned 1.5-10 mc in 2 bands.  The receiver had been modified by WE to "fudge" the AM BC band down so the 500 kc distress frequency could be covered, which lowered the top end of the BC band down as well -- maybe to something like 1200 kc (the tuning cap was straight-line-wavelength, just like most period home BC sets).

This modification of tuning range raised some real interesting questions, among them being how AE could have supposedly received transmissions from BC station KGMB in Honolulu after she went down, which TIGHAR theorizes was on Gardner Island (Nikumaroro) in the Phoenix Group.

Other sources allege that perhaps AE had obtained a Bendix RA-1 receiver via the US Navy.  The Bendix receiver would have either supplanted or replaced the WE unit; the Bendix was a much more capable receiver.  This would have solved the question of her being able to receive at 1300 kc.

AE's transmitter was a 3-frequency, crystal controlled rig originally designed for 2500-6500 kc coverage.  It was tuned for the then-standard airways communications frequencies of 3105 and 6210 kc, and had been factory-modified by WE to also include 500 kc.

Mike Hanz's aafradio dot org web site has information on the transmitter.  The modified unit, which also included CW capability -- not present in the original design -- was called the 13CB.  A schematic is on Mike's site.

The WE gear was cumbersome to operate.  The switchology was involved, and tuning the receiver back and forth from nav to comm frequencies would confuse a lot of us -- let alone AE, who was a radio-doofus.

AE could never have coped with an SCR-183/283; the coil changing alone would have overwhelmed her.  Besides, the power output would have been far too low.  (Her WE 13 ran at 100 watts input.) 

Photo evidence rather clearly nails down the fact that the WE 13-series transmitter was aboard; the receiver is pretty much accepted (by TIGHAR) to have been the companion WE (Model 20...?) but I myself am still open to her having carried a Bendix.

This is a gross oversimplification, indeed a surface-scratching of what is known about AE's comms; but suffice it to say, I would definitely rule out an SCR-183 having been aboard.

By the way, the radio operator she originally planned to take along, Harry Manning,"bailed" on the project after AE cracked up on takeoff from Hawaii on her first attempt at a round-the-world flight.  Reportedly, Manning swore he would "never fly with that woman again!"  They were darn lucky that the overloaded, gas-filled plane didn't turn into a giant fireball when the landing gear collapsed.

AE's navigator, Fred Noonan, had been employed by Pan Americal Airways; and had supposedly qualified as a radio operator for PAA as well -- but the evidence strongly suggests to me that Noonan must have had someone else take the Second Class Radiotelegraph Operator exam for him (!!!!!).  (This license was required for aircraft radio operators.)  That would have been a lot easier to do in 1937 than in modern times.

Neither Noonan nor Earhart had any CW proficiency.  In fact, AE had left her telegraph key behind as a "weight saving" measure.

If there is further interest in this topic, I'll try to answer questions to my best ability.

73

Mike
WA4DLF
--------------------------------------------
On Sun, 8/3/14, WA5CAB--- via ARC5 <arc5 at mailman.qth.net> wrote:

 Subject: Re: [ARC5] Pre-ARC-5 rigs.
 To: arc5 at mailman.qth.net
 Date: Sunday, August 3, 2014, 7:32 PM
 
 Neil,
 
 I haven't really been interested enough in the Earhart
 fiasco to remember 
 most of what I've read about it.  But I didn't think
 there was any question 
 about what radios she carried other than if I recall
 correctly some 
 speculation that she might have dumped some of it.  But
 in any case, the SCR-183 and 
 SCR-283 were at the time current US military sets.  And
 not in plentiful 
 supply.  Although I won't go so far as to say that no
 one could or would have 
 broken the rules, it's highly unlikely that she could have
 gotten her hands 
 on whichever of the two would have worked in her airplane..
 
 Robert Downs - Houston
 wa5cab dot com (Web Store)
 MVPA 9480
 
 In a message dated 08/03/2014 18:09:16 PM Central Daylight
 Time, 
 neilb0627 at gmail.com
 writes: 
 > Yes I see that. OK, I was wrong about the origin of the
 SCR-183/283. I 
 > had
 > assumed that because a coil set in my possession was
 made by W.E. that 
 > that
 > company was the original designer/builder. I was wrong,
 but that doesn't
 > necessarily negate my question about whether Earhart
 carried a W.E.
 > SCR-183/283 set, does it? Or does it?
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