"tony sayer" wrote in message
...
It was eventually determined that there were better, more efficient, and
less troublesome technologies available for broadband delivery, and
dropped,
at least here, although I believe that there may still be some places in
Europe where the tests are still happening. Bear in mind also, that the
generating and distribution companies, use this, or a similar high
frequency
technology, in-house to carry telemetry data around their grid
distribution
network.

What over the 475 kV grid?, don't you mean via the fibre optic at the
top running along the "aerial" earth wire?....

--
Tony Sayer


To Glenn. You've virtually answered your own question there about whether
the mains wiring can successfully handle HF as well as RF, although I was
not actually referring to broadband distribution around the house, rather to
its delivery from the ISP, and this technology has, at least for the time
being, been knocked on the head here, because of potential interference
issues.

To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links, but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did make
use of the full distribution network, including the supergrid, but I may be
wrong on that. How much power volts are on the line, shouldn't make any
difference. It's still just a piece of wire, with HF skin effect, to the
comms signal. I believe that with the PLT internet trials, the injection
points were at central substations, so I guess that this must have been
working at up to at least the local 11kV distribution level. Just as an
aside, I think that the grid and supergrid operate at 275kV and 400kV, not
475kV. I also have a dim recollection of reading somewhere, that the 25kV
overhead lines on the uk rail nework, were also used for HF telemetry, but
again, I could be going off on one there. Suffering from CRAFTs disease,
don'tcha know ... !! d;~}

Arfa

To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links,

Energis.. IIRC used to carry FM broadcast and TV to transmitters.

but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did make
use of the full distribution network, including the supergrid, but I may be
wrong on that. How much power volts are on the line, shouldn't make any
difference. It's still just a piece of wire, with HF skin effect, to the
comms signal. I believe that with the PLT internet trials, the injection
points were at central substations, so I guess that this must have been
working at up to at least the local 11kV distribution level. Just as an
aside, I think that the grid and supergrid operate at 275kV and 400kV,

Yep 400 kV. Even so it would be interesting to see how they get the RF
on and off the line;-!!! wouldn't go through the trannies too well
unless they were using Russ A MK-IV snake oil of course;-))

not
475kV. I also have a dim recollection of reading somewhere, that the 25kV
overhead lines on the uk rail nework, were also used for HF telemetry, but
again, I could be going off on one there.

Never heard of that?.

Suffering from CRAFTs disease,
don'tcha know ... !! d;~}

Errmm hate to admit I do know;-0

Arfa



--
Tony Sayer

"tony sayer" wrote in message
...
To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links,

Energis.. IIRC used to carry FM broadcast and TV to transmitters.

but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did
make
use of the full distribution network, including the supergrid, but I may
be
wrong on that. How much power volts are on the line, shouldn't make any
difference. It's still just a piece of wire, with HF skin effect, to the
comms signal. I believe that with the PLT internet trials, the injection
points were at central substations, so I guess that this must have been
working at up to at least the local 11kV distribution level. Just as an
aside, I think that the grid and supergrid operate at 275kV and 400kV,

Yep 400 kV. Even so it would be interesting to see how they get the RF
on and off the line;-!!! wouldn't go through the trannies too well
unless they were using Russ A MK-IV snake oil of course;-))

not
475kV. I also have a dim recollection of reading somewhere, that the 25kV
overhead lines on the uk rail nework, were also used for HF telemetry, but
again, I could be going off on one there.

Never heard of that?.

Suffering from CRAFTs disease,
don'tcha know ... !! d;~}

Errmm hate to admit I do know;-0

Arfa



--
Tony Sayer


I guess you would get it on and off capacitively. Not too difficult to make
a cap of a few decimals of a uF at several hundred kV working, I would have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ). Also, maybe for use in high
pulse power radar ?

Arfa

I guess you would get it on and off capacitively. Not too difficult to make
a cap of a few decimals of a uF at several hundred kV working, I would have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer

"tony sayer" wrote in message
...
I guess you would get it on and off capacitively. Not too difficult to
make
a cap of a few decimals of a uF at several hundred kV working, I would
have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer


Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ? Thought they were just a bunch of co-phased
dipoles. Bet the launch power from the tx is still a good 2 or 300 kW,
though, and I'd bet that there was a fair whack of volts on the klystron to
get there ...

Arfa

I
Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ?

They stack and phase 'em to get the pattern/gain/and whatever
directivity they want..

Thought they were just a bunch of co-phased
dipoles.

Some are some aren't. Kathrin do some info on theirs...

Bet the launch power from the tx is still a good 2 or 300 kW,

Depends. Take the Heath, IIRC theres a 1000 K going to the North, but
not as much to the South on the analogue stack but the DTV is different
again..

seem to remember it was around 50 -70 K up the pipe..

though, and I'd bet that there was a fair whack of volts on the klystron to
get there ...

15 kV ish IIRC...

Arfa



--
Tony Sayer

"Arfa Daily" wrote in message
...

"tony sayer" wrote in message
...
I guess you would get it on and off capacitively. Not too difficult to
make
a cap of a few decimals of a uF at several hundred kV working, I would
have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer


Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ? Thought they were just a bunch of co-phased
dipoles. Bet the launch power from the tx is still a good 2 or 300 kW,
though, and I'd bet that there was a fair whack of volts on the klystron
to get there ...

Arfa
The high-power UHF TV Transmitters in the UK are 50kW, mostly PyeTVT/Harris
with a number of Marconi as well. The difference between the Tx power and
ERP is entirely made up of antenna gain. UHF antennas have a very narrow
beam, tilted downwards, as there's no point sending power off into space.
The beam is sufficiently narrow so that the signal close to the mast is
actually less than at a distance, also avoiding people's receivers from
overloading.

I don't know how many Klystrons are left in UK service, I would guess a fair
few. Channel 5 was engineered right from the start with Solid State
transmitters, of , if I remember correctly 10kW power, Channel 4 was
klystron originally.

S.

"Serge Auckland" wrote in message
...

"Arfa Daily" wrote in message
...

"tony sayer" wrote in message
...
I guess you would get it on and off capacitively. Not too difficult to
make
a cap of a few decimals of a uF at several hundred kV working, I would
have
thought. You'd then use these to bridge any high inductances in the way,
such as tranny windings, and to get the data on and off. Depending on
the
frequencies involved, you may actually get away with a few hundred pF.

Perhaps but I don't seem to remember seeing much else apart from longish
glass insulators big switch gear and fecking big trannies!...


I'm sure that such caps must have existed when megawatt main UHF TV
transmitter sites, such as Sandy Heath, used valve transmitters at the
bottom of the mast ( perhaps still do ?? ).

Klystons 'tho solid state may be used there now.

Do note that the megawatt etc is radiated power, much more to do with
aerial gains. They don't have megga-watt UHF TV tx'es....


--
Tony Sayer


Yeah, know all about ERPs, but do the flat panel transmission antennas
actually have much gain ? Thought they were just a bunch of co-phased
dipoles. Bet the launch power from the tx is still a good 2 or 300 kW,
though, and I'd bet that there was a fair whack of volts on the klystron
to get there ...

Arfa
The high-power UHF TV Transmitters in the UK are 50kW, mostly
PyeTVT/Harris with a number of Marconi as well. The difference between the
Tx power and ERP is entirely made up of antenna gain. UHF antennas have a
very narrow beam, tilted downwards, as there's no point sending power off
into space. The beam is sufficiently narrow so that the signal close to
the mast is actually less than at a distance, also avoiding people's
receivers from overloading.

I don't know how many Klystrons are left in UK service, I would guess a
fair few. Channel 5 was engineered right from the start with Solid State
transmitters, of , if I remember correctly 10kW power, Channel 4 was
klystron originally.

S.

Thanks Tony and Serge. All interesting stuff. When S.H. UHF was first put
into service, I was an apprentice in the TV trade, and the Rediffusion
branch that I worked for, was chosen to do field strength monitoring by the
IBA, I think it was. Their boys left a receiver with us, with a chart
recorder attached. It was my job to check the tuning of it every morning.
Then it got hit by lightning as I recall, and the very expensive feeder from
Sweden or some such place, got fried. I seem to think that a substitute
piece of pipe from somewhere was put in place to get the site going again,
but there was some VSWR issue with it, because it was a few feet too short
and had to be joined, and whenever the antennas iced up a bit, the SWR seen
by the tx would go just a bit too far out of spec, and the auto protection
would pull it off the air. That tx was never as good after ... Happy days
!! ;-)

Arfa

In article , Arfa Daily
wrote:


To Tony. You're right. In recent years, the electricity companies have
installed fibre optic links, but I'm fairly sure that when they first
started using this method of communicating amongst themselves, they did
make use of the full distribution network, including the supergrid, but
I may be wrong on that. How much power volts are on the line, shouldn't
make any difference. It's still just a piece of wire, with HF skin
effect, to the comms signal. I believe that with the PLT internet
trials, the injection points were at central substations, so I guess
that this must have been working at up to at least the local 11kV
distribution level. Just as an aside, I think that the grid and
supergrid operate at 275kV and 400kV, not 475kV. I also have a dim
recollection of reading somewhere, that the 25kV overhead lines on the
uk rail nework, were also used for HF telemetry, but again, I could be
going off on one there. Suffering from CRAFTs disease, don'tcha know
... !! d;~}

FWIW Barry Fox had an article in the current HFN. There are still companies
trying to use EM signals (not wrapped optical fiber) to send data along the
mains to houses. He was trying to warn audio makers, fans, etc, to object
to this as it might cause some problems. The reason being as others have
indicated - that it is inherently a poor route for such signals, so they
will need to 'shout' to get it to work, thus causing problems to people who
don't want it. However I suspect this will be more of a problem for radio
than for things like amplifiers or CD players *if* it actually succeeds and
is at a high enough level to be a pest.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html