difference technologies

charles henry
5th June 2009, 19:57
As the uk and europe is covered with wires (land line) I wonder if any of the ex sparks there ever got into the higher technology of passing heavy traffic such as hundreds or thousand of voice traffic or multiple TV programs using microwave (Up to 50ghz) or Troposcatter at 900mhz.

Although I spend most of my working life in such I must admit that although it was commonplace to convert TV videos into 45 Mhz digital signals (The audio was on a seperate sub carrier) and then move them to a distant place thousands of miles away........

I must admit that I dont have the slightest notion of how the television set in my house works......

de chas (Pint)

Naytikos
7th June 2009, 07:36
That's how I now make my living. I fear, though, it would bore everyone if I were to launch into a full exposition, so I will keep this short.
We used to use tropo-scatter for telephone/telex service between the Islands and, for a couple of years before the first undersea cable, between us and Jamaica. (I wasn't here then!) There were four circuits. The major consumption of teleprinter paper was caused by random spurious signals generated in the troposphere. It was weird to watch a terminal spring into life and churn out yards of paper with the odd random letter printed.
Now we have an MMDS TV system with 24 channels (or at least it will be when I have rebuilt all of the damaged satellite dishes resulting from last years two hurricanes) and external communications are by undersea fibre-optic cable.

charles henry
7th June 2009, 14:47
That's how I now make my living. I fear, though, it would bore everyone if I were to launch into a full exposition, so I will keep this short.
We used to use tropo-scatter for telephone/telex service between the Islands and, for a couple of years before the first undersea cable, between us and Jamaica. (I wasn't here then!) There were four circuits. The major consumption of teleprinter paper was caused by random spurious signals generated in the troposphere. It was weird to watch a terminal spring into life and churn out yards of paper with the odd random letter printed.
Now we have an MMDS TV system with 24 channels (or at least it will be when I have rebuilt all of the damaged satellite dishes resulting from last years two hurricanes) and external communications are by undersea fibre-optic cable.

Well, as the old saying goes, "being busy keeps you out of the bars".
Interesting for I never thought tropo was used tween the islands but guess anything over 100 miles can use it. Last time I was involved with tropo was in the sixties when I was in Viet nam working for Page engineering. Put in a bunch of systems 1kw and 10kw with 60' and 120' parabolics.

Always felt that tty was invented by the paper companies, often wondered how many zillion trees were used for interminable ryryryryry or the quick brown fox....
de chas

Naytikos
8th June 2009, 04:32
I seem to remember a tropo system connecting Das Island to the mainland. It would be interesting to know how it performed over a whole year given the peculiar varied propagation conditions in the P.G.
Our system had 15m dishes and was dismantled in the mid 80s, reputedly then being installed somewhere in the North Sea.
The incredible paper consumption of TTY systems extended to ship-board SITOR as well. Whilst at Hovic, St Croix, one time, I had to sneak into the refinery offices at dead of night and purloin several rolls from their teleprinter room while the duty watch man was making coffee!

charles henry
8th June 2009, 20:06
[QUOTE=Naytikos;329939]It would be interesting to know how it performed over a whole year given the peculiar varied propagation conditions in the P.G.

A member of
Our company had been an "expert" on tropo design. As a well respected engineer we took his advice, bid only microwave systems (Which is what we manufactured) and when they included a tropo hop we sub'd to Page Engr. After a few drinks he would say, "there are three or four methods of designing a tropo path, you do them all, take the worste, take the poorest results minus an additional 40 db and then bid that one."

However I must admit that Page engr were good at it, installed and turned up about six ranginging from 1kw to 10kw (Now thats what one calls a HUGE KLYSTRON) and they all worked (eventually....)

Klystrons, I remember the tiny little klystron that generated the output power for the small (And wonderfull) Decca marine radar and the first time I saw a high power klystron I simply could not believe my eyes.

Ah, them were the days, been retired for twenty odd years now,
de chas

Ron Stringer
8th June 2009, 20:48
Klystrons, I remember the tiny little klystron that generated the output power for the small (And wonderfull) Decca marine radar and the first time I saw a high power klystron I simply could not believe my eyes.

Which Decca radar was this Charles? The marine radars that I worked on (including some from Decca) all used magnetrons for the output power. Klystrons were used as local oscillators for the receivers. I did later see some comms systems using high power klystrons and even travelling-wave tubes, but never a marine radar using a klystron as the transmitting tube.

charles henry
9th June 2009, 17:27
[QUOTE=Ron Stringer;330234]Which Decca radar was this Charles? The marine radars that I worked on (including some from Decca) all used magnetrons for the output power.

I have to show my age, back in 1954 Decca brought out a tiny little radar, the receiver bolded to a bulkhead or was placed under a settee, the transmitter was under and an integral part of the antenna, thus no waveguide and the info was brought down via slip rings (The weak part of the design but it worked.
At that time 50kw (peak) was considered the lowest power for a marine radar. Forget the actual number but think the peak power was in the order of 100 watts and it was generated by a tiny little reflex klystron. Marvelous machine and it cost only 7,500 quid when all the big boys (like BTH) cost in the 50k and were housed in big "boxes' which were welded to the monkey island.

Forget the actual numbers but for short range they used a REALLY narrow pulse with the result you could pick out a boy in a rough sea. They were cheap, they were physically small and could be fitted on trawlers, tugs and small craft.

When introduced they took the shipping industry like a storm,
regards chas

Ron Stringer
9th June 2009, 19:08
New one on me, Charles. Ah well, still living and learning.

charles henry
9th June 2009, 19:56
New one on me, Charles. Ah well, still living and learning.

Ron, I just realised when Decca brought out that little marvel you were about
fourteen years old.... now I feel so ooooooooooooold
de chas

Ron Stringer
6th December 2010, 17:02
Thought you might sympathise with those having problems in coping with the rate of change in communications practice.

hawkey01
7th December 2010, 11:05
Good one Ron.

Hawkey01