[ARC5] YG,ZB and Lateral to Another Issue.

[Mike Morrow]

Dave wrote:

> With great respect, Mike, this might be "a bridge too far."
> The GF/RU in various iterations was in service as early as 1933,
> which pre-dates the "ZB-type"sets by some years. 

I should have qualified my statement by saying that the ZB should
be an integral part of any RU-*/GF-* that was in carrier service
after the YE/ZB became generally available.  But...it would have
been very difficult to operate outside that constraint. :-)

> Early-Mid-1930s installations had a fixed loop or a DU. 

Yes, I've see quite a few gunner/radio operator cockpit photos
in which the RU, GP, and DU are present.  But later photos often
clearly show the RU, GP and ZB in the same sircraft type.

> I've been trying to find installation docs for Naval Reserve
> installations in 1939 (forlorne hope), which used the GF-10/RU-15
> (the set I'm building).

Was that the "green tag" Naval Reserve designated set that you told
me about?  As the last A.R.C. RU/GF set, that would be a *real* prize.

> I'd be very surprised if "top secret" ZBs had been installed in
> these aircraft or any other non-front-line units during the war
> years.

I'm not sure the system was all that secret.  I have an early-war ZB-3
manual that is classified as RESTRICTED.  Mike Hanz has a later ZB-3
manual that includes the AN/ARR-1 that was classified as CONFIDENTIAL.
He also has ZB homing cards that were CONFIDENTIAL when filled in.
Those can be seen in the Docs section of http://aafradio.org .
As Robert has pointed out, WWII-era CONFIDENTIAL equates to post-war
SECRET, and WWII-era RESTRICTED equates to post-war CONFIDENTIAL
(RESTRICTED classification was eliminated.)  In any event, none of
these classifications are very elevated.  It seems to me that the
purpose and frequency of operation should have been rather more sensitive.
Knowing only that, the enemy could have produced jamming equipment and
VHF direction finding equuipment that would aid in locating the YE/YG
beacons.  But it seems they never did.  Amazing!

> So, in AN/ARC-5, A.R.C. "fix-tuned" the receivers and took away the
> crank.

But only the R-25 to R-27 communications receivers were stabilized and
fix-tuned.  The R-23 and R-24 navigation receivers were not...they always
required the C-26 or C-125 remote tuning units.  The navigation sets weren't
worth stabilizing because in service use they would never rest on only one
pre-set frequency.  In-flight tuning by the pilot would always necessary.

> After knowing all this, why did A.R.C. go back to crank-tuned receivers
> and "broad" IFs to compensate for them in the post-war ARC-type-1x sets?

But...there were no post-war A.R.C. commercial MF/HF communications receivers.
IIRC, the RT-427/ARC-39 in the mid-1950s was their only post-WWII entry into
MF/HF communications equipment production.  In post-war A.R.C. Type 12 world,
the R-23 lived on through the R-11A, as did the R-24 through the R-10A and
R-22.  The normal in-flight utilization of these navigation receivers, just
like their AN/ARC-5 parents, would never be served by having them operate on
only one pre-set frequency.   In-flight tuning by the pilot would always be
necessary.

I detect *no* change of usage or design philosophy between the AN/ARC-5 LF/MF
navigation sets and the A.R.C. post-war commercial LF/MF navigation sets,
other than the local tuning dial was eliminated and, perhaps unwisely, the
BFO was eliminated.  A loop connection remained, through a BNC connector. 

Mike / KK5F