In message , Ralph
Mowery writes

"Ian Jackson" wrote in message
...
The original proposal in this thread was that long antennas performed
better than short ones. If that was true you'd get a good 600MHz UHF TV
picture using a 132ft end fed longwire. I've not tried it, but it doesn't
seem very likely.

A 132' endfed will have one hell of a gain on 600MHz - but it will be
almost straight off the ends.
--
Ian
I know the gain will be off the end of the wire, but still wonder if an
antenna that long (in wavelengths) will actually work or will it be too
long and the gain does not meet the expectations or if programs like NEC
will predict it or fall apart.

On that point, you'll have to ask the experts!


--
Ian

On 30/10/14 22:26, Ian Jackson wrote:
In message , Ralph
Mowery writes

"Ian Jackson" wrote in message
...
The original proposal in this thread was that long antennas performed
better than short ones. If that was true you'd get a good 600MHz UHF TV
picture using a 132ft end fed longwire. I've not tried it, but it
doesn't
seem very likely.

A 132' endfed will have one hell of a gain on 600MHz - but it will be
almost straight off the ends.
--
Ian
I know the gain will be off the end of the wire, but still wonder if an
antenna that long (in wavelengths) will actually work or will it be too
long and the gain does not meet the expectations or if programs like NEC
will predict it or fall apart.

On that point, you'll have to ask the experts!


The gain would be at the cost of a very narrow front lobe. You'd need a
big rotator.

--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk
..
Ubuntu 12.04
Thunderbirds are go.

In message , Frank Turner-Smith G3VKI
writes
On 30/10/14 22:26, Ian Jackson wrote:
In message , Ralph
Mowery writes

"Ian Jackson" wrote in message
...
The original proposal in this thread was that long antennas performed
better than short ones. If that was true you'd get a good 600MHz UHF TV
picture using a 132ft end fed longwire. I've not tried it, but it
doesn't
seem very likely.

A 132' endfed will have one hell of a gain on 600MHz - but it will be
almost straight off the ends.
--
Ian
I know the gain will be off the end of the wire, but still wonder if an
antenna that long (in wavelengths) will actually work or will it be too
long and the gain does not meet the expectations or if programs like NEC
will predict it or fall apart.

On that point, you'll have to ask the experts!


The gain would be at the cost of a very narrow front lobe. You'd need a
big rotator.

In the UK, would you be wanting to rotate it for TV? Don't forget that
one type of antenna used in the very early days of BBC TV (Channel 1,
vertical, 45MHz) was a 'sloper. This was an off-centre-fed wire dipole,
with the short leg being a quarterwave, and attached as high as possible
(maybe to a chimney or a gutter). The other leg was an odd number of
quarterwaves, and attached much lower down. As a result, the antenna had
one of its major lobes sort-of off the end (say 30 degrees off the
wire), in a more-or-less horizontal direction, and responding well to
vertically polarized signals.
--
Ian

"Ian Jackson" wrote in message In
the UK, would you be wanting to rotate it for TV? Don't forget that
one type of antenna used in the very early days of BBC TV (Channel 1,
vertical, 45MHz) was a 'sloper. This was an off-centre-fed wire dipole,
with the short leg being a quarterwave, and attached as high as possible
(maybe to a chimney or a gutter). The other leg was an odd number of
quarterwaves, and attached much lower down. As a result, the antenna had
one of its major lobes sort-of off the end (say 30 degrees off the wire),
in a more-or-less horizontal direction, and responding well to vertically
polarized signals.
--
Ian

I have not kept up with TV signals for a long time. In the US they started
off as all horizontal. I think that some may have gone to circular, but not
sure. It might be the FM stations I am thinking about. Not sure what they
are using now on the digital signals.

What are they using in other countries ? Horizontal, vertical ?



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In message , Ralph
Mowery writes

"Ian Jackson" wrote in message In
the UK, would you be wanting to rotate it for TV? Don't forget that
one type of antenna used in the very early days of BBC TV (Channel 1,
vertical, 45MHz) was a 'sloper. This was an off-centre-fed wire dipole,
with the short leg being a quarterwave, and attached as high as possible
(maybe to a chimney or a gutter). The other leg was an odd number of
quarterwaves, and attached much lower down. As a result, the antenna had
one of its major lobes sort-of off the end (say 30 degrees off the wire),
in a more-or-less horizontal direction, and responding well to vertically
polarized signals.
--
Ian

I have not kept up with TV signals for a long time. In the US they started
off as all horizontal. I think that some may have gone to circular, but not
sure. It might be the FM stations I am thinking about. Not sure what they
are using now on the digital signals.

What are they using in other countries ? Horizontal, vertical ?

Historically, both. The very first UK TV transmitter (45MHz), launched
in 1936, was vertical. This closed down swiftly on 1 September, 1939,
and WW2 started two days later.

After WW2, TV resumed in 1946. Four more channel frequencies (all BBC
only in those days) were added throughout the country in the Low Band
(Band 1, as we call it), and the split of vertical and horizontal was
around 50/50. In 1954, the independent network (ITV) arrived, all in the
High Band (Band 3) - again with around a 50/50 split.

In 1963 (?) UHF was launched - initially carrying only a second BBC
channel, on 625-lines. Eventually, this expanded to four - and in some
places - five channels, all transmissions being co-sited - or almost
co-sited (so that only one, fixed antenna was required). Without
exception, all high(er) power analogue transmitters were horizontal, and
almost without exception, all the low(er)-power fill-in relay stations
were vertical. Although these days it's all digital, same pertains -
except for (I think) one new fairly high power directional vertical
transmitter.

BTW, the old 405-line VHF network was totally closed down in the 1980s.
Although VHF is no longer used for TV, part of the Band 3 allocation is
now digital radio - all vertical. FM was originally all horizontal, but
gradually the benefits of circular - and the simpler mixed -
polarizations became implemented. Very few are now purely horizontal.

Other European countries have had a somewhat different history, but I'm
pretty sure that very few TV transmitters were/are vertical - except for
local fill-in and low power. For FM, the Irish Republic has always
(sensibly) used vertical.




--
Ian

On 31/10/14 00:44, Ian Jackson wrote:
In message , Ralph
Mowery writes

"Ian Jackson" wrote in
message In
the UK, would you be wanting to rotate it for TV? Don't forget that
one type of antenna used in the very early days of BBC TV (Channel 1,
vertical, 45MHz) was a 'sloper. This was an off-centre-fed wire dipole,
with the short leg being a quarterwave, and attached as high as possible
(maybe to a chimney or a gutter). The other leg was an odd number of
quarterwaves, and attached much lower down. As a result, the antenna had
one of its major lobes sort-of off the end (say 30 degrees off the
wire),
in a more-or-less horizontal direction, and responding well to
vertically
polarized signals.
--
Ian

I have not kept up with TV signals for a long time. In the US they
started
off as all horizontal. I think that some may have gone to circular,
but not
sure. It might be the FM stations I am thinking about. Not sure what
they
are using now on the digital signals.

What are they using in other countries ? Horizontal, vertical ?

Historically, both. The very first UK TV transmitter (45MHz), launched
in 1936, was vertical. This closed down swiftly on 1 September, 1939,
and WW2 started two days later.

After WW2, TV resumed in 1946. Four more channel frequencies (all BBC
only in those days) were added throughout the country in the Low Band
(Band 1, as we call it), and the split of vertical and horizontal was
around 50/50. In 1954, the independent network (ITV) arrived, all in the
High Band (Band 3) - again with around a 50/50 split.

In 1963 (?) UHF was launched - initially carrying only a second BBC
channel, on 625-lines. Eventually, this expanded to four - and in some
places - five channels, all transmissions being co-sited - or almost
co-sited (so that only one, fixed antenna was required). Without
exception, all high(er) power analogue transmitters were horizontal, and
almost without exception, all the low(er)-power fill-in relay stations
were vertical. Although these days it's all digital, same pertains -
except for (I think) one new fairly high power directional vertical
transmitter.

BTW, the old 405-line VHF network was totally closed down in the 1980s.
Although VHF is no longer used for TV, part of the Band 3 allocation is
now digital radio - all vertical. FM was originally all horizontal, but
gradually the benefits of circular - and the simpler mixed -
polarizations became implemented. Very few are now purely horizontal.

Other European countries have had a somewhat different history, but I'm
pretty sure that very few TV transmitters were/are vertical - except for
local fill-in and low power. For FM, the Irish Republic has always
(sensibly) used vertical.

VHF FM radio was indeed horizontally polarised at first, and was aimed
at fixed receivers with rooftop aerials. I believe horizontal
polarisation (HP) was first chosen in an attempt to provide greater
coverage than vertical polarisation (VP). AIUI, over a distance from the
TX, a VP transmission twists toward HP as it "grazes" the curvature of
the Earth. In doing so energy gets absorbed and the signal is
attenuated. The arrival of FM car radios meant a growing number of
listeners were using vertical antennas so a change to slant or circular
polarisation was introduced.

The convention for UHF TV stations in the UK was for high powered "main
stations" to use HP and low power relay stations to use VP. This cross
polarisation provided about 26dB protection against co-channel interference.

--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk
..
Ubuntu 12.04
Thunderbirds are go.

Frank Turner-Smith G3VKI wrote in
:

This cross
polarisation provided about 26dB protection against co-channel
interference.


That's a useful figure. I asked a few weeks ago about the prosects of wiring
an external vertical dipole for FM VFH broadcasts, via a MAR6 based
amplifier boosting by maybe 20dB, to an internal horizontal dipole to
overcome local digital hash from nearby flats that gets in to degrade the
signal from a portable radio with a telescopic whip. As it is the SNR rather
than the raw strength which is an issue, an ideal situation would be to allow
thwe whip to be in its resting horizontal, cotracted position, while still
allowing clear use of radios carried around the flat while I work.

Various possible problems have been discussed, and I haven't pushed for this
with a trial, but if 26 or more dB are cut in the difference between antenna
based on polarisation, and the amp boosts only by 20dB, it seems that
feedback can be avoided, AND also the risk of interference to other FM VHF
radios in other flats. (Which might even benefit, if my own would.)

This is the first time anyone's mentioned a figure for isaolation (for want
of a better word) between similar dipoles based on 90° difference in
orientation, so I'm taking this moment to reopen the subject in passing...

On 31/10/14 18:19, Frank Turner-Smith G3VKI wrote:
VHF FM radio was indeed horizontally polarised at first, and was aimed
at fixed receivers with rooftop aerials. I believe horizontal
polarisation (HP) was first chosen in an attempt to provide greater
coverage than vertical polarisation (VP). AIUI, over a distance from the
TX, a VP transmission twists toward HP as it "grazes" the curvature of
the Earth. In doing so energy gets absorbed and the signal is
attenuated. The arrival of FM car radios meant a growing number of
listeners were using vertical antennas so a change to slant or circular
polarisation was introduced.

http://www.bbc.co.uk/rd/publications/rdreport_1960_16

--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.co.uk
..
Ubuntu 12.04
Thunderbirds are go.

On Fri, 31 Oct 2014 00:44:08 +0000, Ian Jackson wrote:

Very few are now purely horizontal.

One of our local community FM stations has a folded dipole at 45 degrees!



--
M0WYM
Sales @ radiowymsey
http://stores.ebay.co.uk/Sales-At-Radio-Wymsey/