On 14/02/2018 09:39, tony sayer wrote:
In article , Phil
Allison scribeth thus
tony sayer wrote:

----------------


Both these transmitters are 250Kw and about 50 miles away.


Actually there're at 125 kW per plane of polarisation thats to say 125 w
in the vertical and 125 horizontal.


** Interesting.


And they aren't totally ommni-directional either in what they do
radiate.


** Nothing like omni-directional, in fact.

Broadcasters are not interested in communicating with ETs or high flying
aircraft so *beam" the available power towards the ground and the horizon - much
like a light house beams its lamp.

Yes indeed. But the Horizontal plane of cover isn't quite "Ommni"
especially on large square or rectangular support masts like the
original FM Station here at Wrotham in Kent. Several tiers of Alan Dick
Spearhead arrays are used..

http://tx.mb21.co.uk/features/wrotham/mixedpol.php


Just because a Transmitter says its "x" kW does not mean that it is in
all directions. Some TV relays are very directional.

To do this multiple antennas are mounted in a vertical line, phased to create a
narrow vertical beam with a wide horizontal pattern. Such a set up boosts the
apparent power of a given transmitter by a factor of 10 or more.

The real RF power behind an advertised "250kW" station is likely to be 10 or
20kW. Saves heaps on the power bills.

Yes it does..


Still a decent 3 or more element aerial up in the clear outside with a
decent feeder and tuner should be quite good....


** Yes, once mounted up high, the roof and everything under it disappears far as
the antenna is concerned.



Yep!, no substitute for Height...


.... Phil




Does this mean, looking at the polar diagrams of the new HP and VP
transmitter, that people to the South-South-West of Wrotham
are better off with a vertical FM aeriel ?.

In article , Andrew Andrew97d-
scribeth thus
On 14/02/2018 09:39, tony sayer wrote:
In article , Phil
Allison scribeth thus
tony sayer wrote:

----------------


Both these transmitters are 250Kw and about 50 miles away.


Actually there're at 125 kW per plane of polarisation thats to say 125 w
in the vertical and 125 horizontal.


** Interesting.


And they aren't totally ommni-directional either in what they do
radiate.


** Nothing like omni-directional, in fact.

Broadcasters are not interested in communicating with ETs or high flying
aircraft so *beam" the available power towards the ground and the horizon -
much
like a light house beams its lamp.

Yes indeed. But the Horizontal plane of cover isn't quite "Ommni"
especially on large square or rectangular support masts like the
original FM Station here at Wrotham in Kent. Several tiers of Alan Dick
Spearhead arrays are used..

http://tx.mb21.co.uk/features/wrotham/mixedpol.php


Just because a Transmitter says its "x" kW does not mean that it is in
all directions. Some TV relays are very directional.

To do this multiple antennas are mounted in a vertical line, phased to create
a
narrow vertical beam with a wide horizontal pattern. Such a set up boosts the
apparent power of a given transmitter by a factor of 10 or more.

The real RF power behind an advertised "250kW" station is likely to be 10 or
20kW. Saves heaps on the power bills.

Yes it does..


Still a decent 3 or more element aerial up in the clear outside with a
decent feeder and tuner should be quite good....


** Yes, once mounted up high, the roof and everything under it disappears far
as
the antenna is concerned.



Yep!, no substitute for Height...


.... Phil




Does this mean, looking at the polar diagrams of the new HP and VP
transmitter, that people to the South-South-West of Wrotham
are better off with a vertical FM aeriel ?.

You Might be but very much a case of trial and error!
--
Tony Sayer