In article , Bill Wright
scribeth thus
tony sayer wrote:

Just in case anyone on the group missed this one)...


http://www.eafa.org.uk/catalogue/861

In the first pic the reflector on the 8-ele ITV aerial has slipped down
inside the element clip. They were able to do that so they could be slid
along to allow the box to be shorter.

Not also the unusual BI dipole and reflector.

If it was supposed to be about Mendelsham how come the aerials are VP?
That's what I'd like to know!

And then there's that really weird double UHF aerial on the left!

And if it was 1959 why are there UHF aerials anyway?


Well that film was made sometime after the TX opened and I suppose like
all well informed jurno's and film makers they assumed that one TV
aerial is much as the same as the other and then others;!...

--
Tony Sayer

On Fri, 30 Dec 2011 21:09:05 +0000, tony sayer
wrote:

In article , Stephen
Wolstenholme scribeth thus
On Wed, 28 Dec 2011 19:08:23 +0000, Peter
wrote:

On Tue, 27 Dec 2011 13:46:16 +0000, Stephen Wolstenholme
wrote:

On Mon, 26 Dec 2011 17:04:37 -0800 (PST), David Paste
wrote:

A while back, there was a tale about the retirement of the microwave
dishes on the BT tower in London due to the introduction of new
technology (fibre optics?). As I understand it, there are a series of
BT microwave towers around the country, at least, there is one in
Heaton Park in Manchester. So what is to happen to these towers if the
network is going to F/O?

Thanks,

David Paste.

They will all be back in use when someone points out to BT that
microwaves don't need thousands of miles of digging!

BT are well aware of that. However to match the capacity of one fibre
pair, lets say 320Gb of traffic lets try and work out how many
microwave dishes would be needed and how tall the masts or towers woud
need to be.

320Gb equals 32 X STM64 which equals 2048 STM1's

The last BT trunked radio I worked on had the capacity of 4+1 STM1's,
so to replace 1 320Gb fibre pair you would need around 400 radio
systems - that's an awful lot of dishes :-)

And that only one fibre pair!!!

I'm thinking about reusing the towers not the dishes. I'm sure
microwave communications will be improved with different dishes.
There's a rectangular one near here about the size of a soap powder
packet up the top of telegraph pole. What would that be for?


Prolly Internet backhaul or a short range 5.8 Ghz link.

Its all economics in essence. A fibre can and does carry a lot more then
what a microwave link can, well over the sort of distances required for
national links. Locally you can get some very high capacities up in the
G/Bit region but only over short "ish" distances.

Its not a very good tech Microwave for national links now compared to
fibre if Microwave was that good why do you think BT went to all the
bother of not replacing the dishes they had on the London tower?..

microwave can do 622 Mbps on a good day, + double it with crossed
polarisation - 1 Gbps round numbers

state of the art on fibre is 200+ lambdas of 40 Gbps (and likely to go
to 100 Gbps lambdas soon)
or 90 x 100 Gbps depending on the kit.

so about 10^4 difference

Fibre regen distance is 100 to 400 Km - but a composite amplifier will
handle all the lambdas without separate electronics per lambda, for up
to 3000 Km or so.

And why when the BBC mast at Peterborough fell down some years ago BT
cleaned up there one next door so much hardly anything is left on it
now....



Steve

--
Regards

- replace xyz with ntl

On Tuesday, December 27th, 2011, at 19:08:40h +0000, Mark Carver explained:

Actually more of a concern is a gust of wind blowing the
street cabinet over !

Or the local youth organisation doing a stress test upon
or torching the cabinet?