[ARC5] Re: Odd GF xmtr coil set mystery??

[David Stinson]

"Thekan, Paul" wrote:
> 
>  I came across what looks to be a xmtr coil set for the GF series of xmtr.
> What I found odd was the freq. range which is 1000 - 1250 Kc . I was not
> aware that the GF xmtr operated down that far. Also directly underneath
> where the freq. range is etched on the nomenclature plate is also etched
> Serial X  Also where the Type and Serial number info would be stamped or
> written in - it is blank except for CBY-   The coils set was made by A.R.C.
> as a No. 2929 coil set. The contract number is N156S-19737 and dated 7-1-41

This is a "preliminary" reply, since I don't have all the 
data together to hard-n-fast confirm what follows, but 
it looks pretty good.  Indeed, with the destruction of Navy 
records under the last administration, such confirmation
may never exist.  We'll have to make do with what we can find.
One of our members once posted that he could hear Navy aircraft
and ships on the broadcast band down on the gulf coast.  
He was right.

None of the GF transmitters were issued with this MF coil, 
or the one Mike Hanz so kindly sent me, as a standard item.  
By 1941, the Navy was already into production of the the last of
the GFs, the GF-12, and it was issued with normal HF coils.  

The nomen plates state they are "FOR MODEL GF SERIES EQUIPMENT,"
so these coils, probably plus one for 1500-2000 KC and one or more
for under 1000 KC were meant to service any GF transmitter 
beyond GF-2.  Not coincidentally, the planning for production of
Longwave transmitters for ATA and AN/ARC-5 would have begun 
about this time, since there are T-15s and T-16s with 1943 
inspection dates.  While there were plans for similar 
longwave ATA sets per Gordon White, none are known to exist.
In researching these coils, we may at last have a good answer 
for why they and the T-15, T-16 and T-17 AN/ARC-5 transmitters
were produced.

As most of you remember, I have two veteran accounts of the 
MF ARC-5 transmitters being used as "surrender now" 
broadcast transmitters and for DF spoofing. 
A veteran witness should never be discounted and, 
given the vast amount of "on the fly" innovation and 
non-standard, expedient installations we have documented, 
I have no doubt whatever that such applications took place.
But building an entire run of equipment with these uses first
in mind doesn't seem reasonable.  
There must have been a larger need for such an expensive procurement, 
and there was such a need.

In the 1920s and 30s, most naval communication
was conducted on LF and MF, up to about 2000 KC.
This was where the famous "200 meters and down" 
allocation for hams originated.  
In 1926, many allied nations met in Washington for a joint
Naval Radio Conference.  One of the products of this meeting 
was the U.S. Naval Communications Frequency Plan.
The naval and coast forces of many allied countries, 
especially in the western hemisphere, adopted this plan
in whole or in part.  Frequency ranges allocated for 
naval aircraft were 1000 to 1295 KC and 3005 to 3985 KC.
More importantly, fleet tactical and strategic frequencies-
those which ships used to communicate with each other,
with shore *and to liaison with units of other nations*- 
were almost entirely below 2000 KC.
Many nations adopted this plan as it provided for 
joint exercises without serious communications problems 
between allied units.

As WWII approached, the U.S. and British navies 
began using much higher frequencies on a routine basis, 
*but this was not general throughout the world.*  
The naval and coastal forces of most smaller, 
less rich countries retained the old LF and MF equipment.  

Thus, if there were to be joint exercises between 
U.S. forces and those of Brazil,
or if a U.S. PB4Y was to coordinate 
an attack on a U-Boat with a Mexican destroyer, 
or cooperation on rescuing a downed flyer 
between U.S. aircraft and a coastal vessel from Iran, 
a tactical-level voice transmitter
capable of MF/LF operation would have been indispensable.
Therefore, I propose (and hope to acquire additional data
to confirm) that the problem of U.S. aircraft communicating
and coordinating with the naval assets of less developed 
allied nations was the root cause for the production of 
these GF coils, the plans for LF ATAs and the later
production of LF/MF AN/ARC-5 transmitters.

73 OM DE Dave Stinson AB5S

P.S. Paul, if I can't tempt you into a good trade for your coil 
to go with this one, could I please request a good photo of 
then nomenclature plate and any inspection stamps for the database?