On 24/11/2022 17:46, Jim Lesurf wrote:
> Behind a high gain antenna there may be a near-null away from the antenna
> on its extended beam axis.

I remember many years ago seeing an article in a magazine that showed
the polar diagrams for various TV receiving antenna when used on the
wrong groups.

You tend to think that they will just have a bit less gain etc but many
had lobes going in all sorts of directions and even often no gain in
what might have been thought to be the front where the gain is wanted.

Charles and Bill will remember that when new UHF TV relays came on,
there would be often be the proverbial "men in white vans" going around
offering to fit new antenna cheaper than local dealers. Apart from
shoddy workmanship and cheap cable, they often had cheap antenna. In a
number of areas where there were low channels in use, it was often found
these antenna did not work down to Ch.21

On 24/11/2022 10:37, Mark Carver wrote:
>
> I install CODFM based wireless mics and cameras in TV studios. The Rx
> antennas are often up in the lighting grid, in a jungle of metal work.
> I've never heard or seen disturbance, and the devices often carry on
> with useful output a surprising distance away from the studio....

And don't they always work surprisingly well when someone famous says
something unwise believing they're off mic!

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

On Friday, 25 November 2022 at 09:57:41 UTC, MB wrote:
> On 24/11/2022 17:46, Jim Lesurf wrote:
> > Behind a high gain antenna there may be a near-null away from the antenna
> > on its extended beam axis.
> I remember many years ago seeing an article in a magazine that showed
> the polar diagrams for various TV receiving antenna when used on the
> wrong groups.
I had something like that published in a mag a good few years ago. I have a field behind the house that is big enough to carry out meaningful antenna tests, and at different times I did all sorts of things.

> You tend to think that they will just have a bit less gain etc but many
> had lobes going in all sorts of directions and even often no gain in
> what might have been thought to be the front where the gain is wanted.

Yes. A polar diagram looking like a starfish.
>
> Charles and Bill will remember that when new UHF TV relays came on,
> there would be often be the proverbial "men in white vans" going around
> offering to fit new antenna cheaper than local dealers. Apart from
> shoddy workmanship and cheap cable, they often had cheap antenna. In a
> number of areas where there were low channels in use, it was often found
> these antenna did not work down to Ch.21
Many such aerials were installed using the Sheffield (Crosspool) relay. When Channel Four started (late) on ch21 the shit hit the fan. See
http://www.wrightsaerials.tv/articles/whatsat-short-reflector-syndrome.pdf
Bill

On 22/11/2022 15:23, NY wrote:
> - The wind unit is a bit low, probably only about 10 cm higher than the
> ridge tiles of the roof, which may lead to "boundary effects" with the
> wind and the ridge, and hence lower window speeds and maybe some bias on
> the direction. Unless I get a longer ladder, I've got it as high as I can.

And as a sailor, but not an aerial engineer, that's the bit that matters.

If you want an accurate reading off your wind vane it needs to be
significantly higher that the roof and all the other chimneys. Not to
mention the trees you mentioned.

Once you've got the van working accurately it's not going to be
interfering with the aerial.

Andy

"Vir Campestris" <vir.campestris@invalid.invalid> wrote in message
news:tltjid$1e0fa$2@dont-email.me...
> On 22/11/2022 15:23, NY wrote:
>> - The wind unit is a bit low, probably only about 10 cm higher than the
>> ridge tiles of the roof, which may lead to "boundary effects" with the
>> wind and the ridge, and hence lower window speeds and maybe some bias on
>> the direction. Unless I get a longer ladder, I've got it as high as I
>> can.
>
> And as a sailor, but not an aerial engineer, that's the bit that matters.
>
> If you want an accurate reading off your wind vane it needs to be
> significantly higher that the roof and all the other chimneys. Not to
> mention the trees you mentioned.

Yes I need to borrow a neighbour's three-section extending ladder rather
than my two-section extension/A-frame convertible ladder. Hopefully I can
extend it just far enough so the top of the uppermost section touches the
house wall just below the gable end, directly below the aerial pole, and
then tie it to the brackets sticking out of that gable end which support the
pole. That will allow me to move the wind vane further up the pole so it is
50 cm above the ridge. The nearest chimney is about 10 metres away, which
may be a bit close but hopefully not too bad. I'm after a good approximation
of speed and direction rather than Met Office-compliant figures.

Trying to get the vane clear of trees would be a real pain: there are
various tall pine trees much higher than the house, the closest being about
30 metres away. Fortunately they are in a line which is roughly a radius
extending from the pole so they only block (partially) one compass bearing.

There is a much higher gable end, on a two-storey part of the house, whereas
the aerial is on a long pole which raises the aerial to roughly two-storey
height but fastened to a one-storey pat of the house. But that would need
major work to fasten a pole (with stand-off brackets so it clears the
overhang of the roof) into the brickwork. That may be beyond my skill and
courage level (working at that height) and may invoke SWMBO's "we need to
get a *man* in to do that" clause. At least the aerial pole is already
present.

When I had a weather station at our previous house it was mounted a lot
lower (about 3 metres above the ground) and was blocked by our terrace of
houses for about 120 degrees compass bearing. But it was about 50 metres
away, and that seemed to let enough wind around to give sensible wind
bearings - the acid test was that the weather station's diagram of
prevailing wind directions over the past few hours did not have a huge
"hole" corresponding to the directions which were blocked by the house.
Being in a middle terrace at that house, I didn't have the option of
mounting the weather station on a gable end, though I could have got an
aerial engineer to put it on the chimney-mounted aerial pole while he was
fitting the new aerial that we needed. Anyway, all that's in the past.

One thing I need to consider: my weather station remote senders (one does
wind speed/direction and the other in a different location does
temp/humidity/rain) have non-rechargeable batteries which need replacing
every few years (they provide power for night-time readings when there is no
sun for the sensors' solar panels) so I need to be able to reach the wind
one occasionally when it reports low battery. Why they didn't opt for
rechargeable batteries, which have a much longer life as long as they are
charged during the day, is a mystery. But Davis (the maker) said that a
rechargeable battery, even if they make one in that size/voltage), is not an
option because the solar panel has no way of feeding power to the battery.

On 26/11/2022 04:18, wrightsaerials@aol.com wrote:
>
>> Charles and Bill will remember that when new UHF TV relays came on,
>> there would be often be the proverbial "men in white vans" going around
>> offering to fit new antenna cheaper than local dealers. Apart from
>> shoddy workmanship and cheap cable, they often had cheap antenna. In a
>> number of areas where there were low channels in use, it was often found
>> these antenna did not work down to Ch.21
> Many such aerials were installed using the Sheffield (Crosspool) relay. When Channel Four started (late) on ch21 the shit hit the fan. See
> http://www.wrightsaerials.tv/articles/whatsat-short-reflector-syndrome.pdf
Didn't you mention also in the early days of UHF, a firm based in
Newbury were producing Group B yagis, except their idea of Group B, was
what we had locally here from Hannington [1].
39, 42, 45.
All fine, until you try it on Emley, 44, 47, 51 ?!

Of course Hannington was never referred to as Group B by either the BBC
or the IBA, it was Group E because C4 was always going to be on 66, but
that's another story....

On Sunday, 27 November 2022 at 19:49:27 UTC, Mark Carver wrote:

> > Many such aerials were installed using the Sheffield (Crosspool) relay. When Channel Four started (late) on ch21 the shit hit the fan. See
> > http://www.wrightsaerials.tv/articles/whatsat-short-reflector-syndrome.pdf
> Didn't you mention also in the early days of UHF, a firm based in
> Newbury were producing Group B yagis, except their idea of Group B, was
> what we had locally here from Hannington [1].
> 39, 42, 45.
> All fine, until you try it on Emley, 44, 47, 51 ?!

Yes, what a fine memory you have, Mr Carver! The aerials were hopeless on ch51, quite obviously a long way down the steep gain slope that characterises yagis used above the design frequency. The salesman in Yorkshire was a very amiable chap. I met him years later in a layby. He was then employed selling Mars Bars etc to shopkeepers.

Some very early UHF aerials (almost experimental) were specific for one channel. Round these parts it was ch51.

Bill

On 23/11/2022 09:28, Davey wrote:
> On Wed, 23 Nov 2022 09:14:39 -0000
> "Brian Gaff" <brian1gaff@gmail.com> wrote:
>
>> Get a plastic Weather vane.
>> Brian
>>
> The one I am thinking of getting is a bespoke one, which only comes in
> mild steel.
By the way, you could lash up a dummy Weathervane made up of tinfoil and
cardboard, and try that in the vicinity of your aerial.
That would be a valid experiment.

In article <tlu2q0$1fddb$1@dont-email.me>, NY <me@privacy.invalid> wrote:
>... Why they didn't opt for rechargeable batteries, which have a much
> longer life as long as they are charged during the day, is a mystery.
> But Davis (the maker) said that a rechargeable battery, even if they
> make one in that size/voltage), is not an option because the solar panel
> has no way of feeding power to the battery.

Curous. My instant thought was that the sides of a weathervane should be Ok
as surfaces to fit some 'solar panels' to keep a small battery charged. Has
no-one even tried this? In effect, use a pair of shaped back-to-back solar
panels as the vane.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

On Mon, 28 Nov 2022 09:47:39 +0000
Mark Carver <mark.carver@invalid.invalid> wrote:

> On 23/11/2022 09:28, Davey wrote:
> > On Wed, 23 Nov 2022 09:14:39 -0000
> > "Brian Gaff" <brian1gaff@gmail.com> wrote:
> >
> >> Get a plastic Weather vane.
> >> Brian
> >>
> > The one I am thinking of getting is a bespoke one, which only comes
> > in mild steel.
> By the way, you could lash up a dummy Weathervane made up of tinfoil
> and cardboard, and try that in the vicinity of your aerial.
> That would be a valid experiment.

True.
--
Davey.

NY wrote:

> Davis (the maker) said that a rechargeable battery, even if they make one in
> that size/voltage), is not an option because the solar panel has no way of
> feeding power to the battery.

Slip rings? Inductive charging à la toothbrush?

On Wed, 23 Nov 2022 19:20:03 -0800 (PST)
"wrightsaerials@aol.com" <wrightsaerials@f2s.com> wrote:

> On Wednesday, 23 November 2022 at 11:58:23 UTC, Davey wrote:
>
> > It does sound as though there is too much to risk, especially with
> > a bespoke weathervane, which could not be returned fro a refund if
> > it affected the signal
> > I may have to abandon this idea. At least I have investigated it.
> > Thanks for the answers, everyone.
> >
> > --
> > Davey.
>
> In all my many years of TV aerial installation I've never had this
> problem. There are lots of large metal chimney cowls that move round
> when the wind changes and I've never known of one causing a problem.
> Many schools have weather vanes and they don't cause a problem. In
> the worst case scenario the weather vane might cause a reflection
> that arrived at the aerial exactly out of phase with the main signal,
> but even so that would merely cause a small fluctuation in signal
> strength which would have no effect on reception, because the
> reflection wouldn't be anywhere near as strong as the main signal, so
> significant phase cancellation wouldn't happen. Some years ago I
> carried out a lot of surveys of the effects of ginormous wind
> turbines on TV reception. Once digital came along it was next to
> impossible to find any such effects because of the way digi works.
> There were zero effects from reflections off the whacking great
> blades. You could see the slight fluctuations in signal level on the
> analyser but it was never anywhere near enough to affect reception.
> It was possible to get visible-on-the-screen effects when the signal
> was very weak and the path was through the area encompassed by the
> blades, but that was all. Buy your weathervane and get it installed.
> In the stupendously unlikely event that it affects your TV reception
> consider: 1. moving the TV aerial up or down a bit 2. Installing a
> slightly taller mast than you envisaged, with the weather vane at the
> top and the TV aerial beneath it, or vice versa. But it won't happen.
> Bill

I have hone ahead with the weathervane. The supplier has no option for
plastic on bespoke weathervanes, but is adamant that there will be no
effect on TV reception.
Let's hope. I have it in an e-mail message, if there is a problem.

--
Davey.

"Davey" <davey@example.invalid> wrote in message
news:tm7c1a$2gu1d$6@dont-email.me...
> I have hone ahead with the weathervane. The supplier has no option for
> plastic on bespoke weathervanes, but is adamant that there will be no
> effect on TV reception.
> Let's hope. I have it in an e-mail message, if there is a problem.

Good luck. Let us know whether everything works when you get the vane
mounted on the aerial pole.

On Wednesday, 30 November 2022 at 10:41:48 UTC, Davey wrote:

> I have hone ahead with the weathervane. The supplier has no option for
> plastic on bespoke weathervanes, but is adamant that there will be no
> effect on TV reception.
> Let's hope. I have it in an e-mail message, if there is a problem.
>
> --
> Davey.
So you'd rather believe a person with no likely experience or knowledge, but does have a vested interest in selling, than those here who know a great deal about RF propagation?
Bill

On Wed, 30 Nov 2022 07:38:36 -0800 (PST)
"wrightsaerials@aol.com" <wrightsaerials@f2s.com> wrote:

> On Wednesday, 30 November 2022 at 10:41:48 UTC, Davey wrote:
>
> > I have hone ahead with the weathervane. The supplier has no option
> > for plastic on bespoke weathervanes, but is adamant that there will
> > be no effect on TV reception.
> > Let's hope. I have it in an e-mail message, if there is a problem.
> >
> > --
> > Davey.
> So you'd rather believe a person with no likely experience or
> knowledge, but does have a vested interest in selling, than those
> here who know a great deal about RF propagation? Bill

Says the man who told me:
"In all my many years of TV aerial installation I've never had this
problem."

Talk about mixed messages!
--
Davey.

On Wednesday, 30 November 2022 at 18:43:49 UTC, Davey wrote:
> On Wed, 30 Nov 2022 07:38:36 -0800 (PST)
> "wrights...@aol.com" <wrights...@f2s.com> wrote:
>
> > On Wednesday, 30 November 2022 at 10:41:48 UTC, Davey wrote:
> >
> > > I have hone ahead with the weathervane. The supplier has no option
> > > for plastic on bespoke weathervanes, but is adamant that there will
> > > be no effect on TV reception.
> > > Let's hope. I have it in an e-mail message, if there is a problem.
> > >
> > > --
> > > Davey.
> > So you'd rather believe a person with no likely experience or
> > knowledge, but does have a vested interest in selling, than those
> > here who know a great deal about RF propagation? Bill
> Says the man who told me:
> "In all my many years of TV aerial installation I've never had this
> problem."
> Talk about mixed messages!
> --
> Davey.
If I've never had the problem in a lifetime of work that means it's disappearingly unlikely that you will have it in one installation.
Bill

On Wed, 30 Nov 2022 20:10:14 -0800 (PST)
"wrightsaerials@aol.com" <wrightsaerials@f2s.com> wrote:

> On Wednesday, 30 November 2022 at 18:43:49 UTC, Davey wrote:
> > On Wed, 30 Nov 2022 07:38:36 -0800 (PST)
> > "wrights...@aol.com" <wrights...@f2s.com> wrote:
> >
> > > On Wednesday, 30 November 2022 at 10:41:48 UTC, Davey wrote:
> > >
> > > > I have hone ahead with the weathervane. The supplier has no
> > > > option for plastic on bespoke weathervanes, but is adamant that
> > > > there will be no effect on TV reception.
> > > > Let's hope. I have it in an e-mail message, if there is a
> > > > problem.
> > > >
> > > > --
> > > > Davey.
> > > So you'd rather believe a person with no likely experience or
> > > knowledge, but does have a vested interest in selling, than those
> > > here who know a great deal about RF propagation? Bill
> > Says the man who told me:
> > "In all my many years of TV aerial installation I've never had this
> > problem."
> > Talk about mixed messages!
> > --
> > Davey.
> If I've never had the problem in a lifetime of work that means it's
> disappearingly unlikely that you will have it in one installation.
> Bill

No argument. But it was your comment, above, about preferring the advice
of others over yours that confused me.
--
Davey.

In article <jumth5Fsdt4U1@mid.individual.net>, Andy Burns
<usenet@andyburns.uk> wrote:
> NY wrote:

> > Davis (the maker) said that a rechargeable battery, even if they make
> > one in that size/voltage), is not an option because the solar panel
> > has no way of feeding power to the battery.

> Slip rings? Inductive charging à la toothbrush?

Apart from "being arsed" or "keep it cheap" there's no reason not to use
inductive or cap transfer.

FWIW Given you'd need a downlead for the power captured (and for any remote
reading of the vane's info) they could also give the vane an extra
horizontal tail, say, to get more energy. Could then also become a weather
station showing temperature, etc, as well as giving some energy. All
depends on the level of being bothered, and cost.

What would then sell and make a profit is another matter. Problem may be
over-caution by makers who assume no profit to be made. Not a design
problem.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
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