All, this is slightly off topic. Well, maybe it's a lot off topic from relevancy
point of view.
The message which follows may be of particular interest to the FBBW
crowd. It was placed on the Compuserve Telecom Forum board by one my
long-standing 'net acquaintances there, Mr. Albert LaFrance. Albert has
done a lot of exploration of ancient telco infrastructure, silos used during the
cold war, and the old ATT coaxial L4 plant as it related to bomb-hardened
underground military sites. Another area of interest has been microwave
towers and other structures used to support wireless transmission systems
of all types. A recent discussion even focused on the WT-4 hollow
microwave waveguide system (actually helically constructed, if memory
serves me right) that ATT Long Lines experimented with, until the advent
of fiber optic systems.
The following was posted today, and I reprint it here with Albert's
permission for your edification and enjoymnet.
See Albert's questions at the end of the message. If anyone has the answers
he seeks, please reply here, or in PM to me and I will see to it that he receives
them.
Regards, Frank_C.
---------Begin History Lesson:
[All],
In researching old military communications systems at the National
Archives, I came across something which might be of historical interest. In
a list of documents from the U.S. Army Office of the Chief Signal Officer,
I found a couple of files related to a "Pentagon - Fort Monroe Microwave
Relay". What got my attention was that the documents were very old,
going back as far as 1946.
The files contain records of an experimental microwave link between the
Pentagon and the headquarters of the Army Ground Forces at Ft. Monroe,
VA (near Hampton). The link was proposed in a July 1946 memo. It was
to have six manned relay points, listed from north to south in an August
1946 memo:
- Episcopal High School (near Fort Ward Park), Alexandria, VA - I suspect
this site was needed only because of the low elevation and short (50 ft.)
tower at the Pentagon. Later memos mentioned elimination of this site,
apparently due to installation of taller towers and relocation of other sites.
- La Plata (Pomfret), MD - There was a big Army HF receiving station
here.
- Peeds (Leedstown), VA
- Laneview, VA
- Amburg (Duck Pond), VA
- Severn, VA
As of July 1947, the "Provisional Radio Relay Platoon" had a complement
of three officers and 45 enlisted men. There were many operational
problems, including poor utility power quality, inadequate towers,
deficiencies in equipment performance, and adjustments which required lots
of tower climbing. One of the non-technical difficulties was the lack of a
cash fund to pay toll bridge charges for travel between two of the relay
sites. The bridge had new owners who no longer allowed the soldiers to
sign for the charges, thus requiring a 100-mile detour.
The stations were only attended during business hours, which were
changed slightly during the winter months to compensate the men for the
hardships of the more isolated sites. The equipment was left on
continuously, but availablility of the link outside of attended hours was a
matter of luck. Backup was, of course, provided by landline telephone
circuits.
By August 1947 it was decided that the link could not remain on the air for
traffic due to a shortage of trained personnel, but that it was valuable for
experimental purposes. In a great example of double-speak, it was decided
that the link is "...not wholly experimental but semi-permanent".
In a December 1947 memo, a lieutenant challenges the assertion that the
personnel were up to the job of running the system. He says that the men
are not really technicians, but are more appropriately termed "operators",
that they lack knowledge of radio theory, do not know how to use tools and
test instruments, and, in his most devastating observation, noted that "some
of the men are not interested in microwave work". The lieutenant
concluded that some of the men are more trouble than they are worth.
The solution was to put the system on hold for a while, send the
short-timers back to the company, and recruit people with more aptitude
and motivation, who would undergo training with Western Union to become
fully-qualified "microwave attendants".
The link operated at 4950 MHz. It was originally 4350, until the Army
found that the frequency wasn't authorized. As of October 1948, the radio
equipment was the AN/TRC-5 (XC-4) and AN/TRC-6 (XC-4). I think the
"XC-4" suffix indicates experimental or pre-production equipment; earlier
documents mention lower-numbered suffixes. A 1948 memo noted that a
new generation of equipment, the AN/TRC-24 and -25, was under
development.
The transmitters used type 2K-55 klystrons. It was determined that a
minimum output of 200 mw was needed for satisfactory operation.
The link was originally configured with 8 voice channels, one of which was
to carry 4 TTY circuits (expandable to 12). The maximum capacity was 6
voice channels and 4-12 duplex TTY circuits.
It appears that the terms "UHF" and "microwave" were used
interchangeably in that era. For example, a proposed training program
being developed by the Army Signal School was named "UHF Radio Relay
Repairman Course", yet the outline dealt with microwave topics, and the
course was intended to produce a "microwave maintenance man".
I don't know what finally became of the link, because the files don't go
beyond 1948. The later records, if any, are probably still classified - not
because they're sensitive (at least I hope not!), but rather because they're
not quite 50 years old and thus are not yet due for mandatory
declassification. I will request a declassification review of any more recent
records, though I don't know how long that will take.
...Albert
-------------End Lesson
ps - It would be particularly interesting to hear from anyone familiar with
the equipment used. I've looked at a couple of web pages listing military
comms gear, but they don't seem to go back that far.
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