Further to the recent discusssion about UHF TV aerials and their reputed 
performance, I can report that this morning I received through the post a 
flier advertising the Wolsey QR12 WF aerial. The gain is quoted as "14dB". 
There is also a graph showing the gain against UHF channels. Not so close 
examination shows that the gain only equals or exceeds 14dB on channels 65 
to 69 incl. On channel 21 it is 7dB; on channel 33 it is 8dB, and on channel 
52 it is 10.5dB.

Bill

"Bill Wright"  wrote in message 
news:PfqdneGf5I90Fc_VnZ2dnUVZ8sTinZ2d@pipex.net...
> Further to the recent discusssion about UHF TV aerials and their reputed 
> performance, I can report that this morning I received through the post a 
> flier advertising the Wolsey QR12 WF aerial. The gain is quoted as "14dB". 
> There is also a graph showing the gain against UHF channels. Not so close 
> examination shows that the gain only equals or exceeds 14dB on channels 65 
> to 69 incl. On channel 21 it is 7dB; on channel 33 it is 8dB, and on 
> channel 52 it is 10.5dB.
>
> Bill
>
You should know by now that gain figures are meaningless.  Around the days 
of
CB the figures were plucked from the air to sell a product.  People quoted
various wild claims for performance.  None of which were true. 
Unfortunately the
same people must have grown up and gone in to TV aerial manufcturing.  How
often do you see a 10 element aerial advertised as 40 elements if in an "X" 
shape.
It's all completely meaningless, so are CAI recommendations as they appear
proportional to the donation!

"john m" <john@nospam.2net> wrote in message 
news:g2udcm$au0$1@news.albasani.net...
>
> "Bill Wright"  wrote in message 
> news:PfqdneGf5I90Fc_VnZ2dnUVZ8sTinZ2d@pipex.net...
>> Further to the recent discusssion about UHF TV aerials and their reputed 
>> performance, I can report that this morning I received through the post a 
>> flier advertising the Wolsey QR12 WF aerial. The gain is quoted as 
>> "14dB". There is also a graph showing the gain against UHF channels. Not 
>> so close examination shows that the gain only equals or exceeds 14dB on 
>> channels 65 to 69 incl. On channel 21 it is 7dB; on channel 33 it is 8dB, 
>> and on channel 52 it is 10.5dB.
>>
>> Bill
>>
> You should know by now that gain figures are meaningless.  Around the days 
> of
> CB the figures were plucked from the air to sell a product.  People quoted
> various wild claims for performance.  None of which were true. 
> Unfortunately the
> same people must have grown up and gone in to TV aerial manufcturing.  How
> often do you see a 10 element aerial advertised as 40 elements if in an 
> "X" shape.
> It's all completely meaningless, so are CAI recommendations as they appear
> proportional to the donation!

That line of thought worries me immensely. Without the benchmarking, what 
have we got to refer to?

Most of the regular posters on this group are technically literate people 
who, through work or hobbies know their way around a TV installation. 
However beside Justin from ATV who tests everything in a madcap test lab on 
top of a Yorkshire hill, and Bill, Carpy and Glenn who can make meaningful 
comparisons on rooftops from the stock in their vans, what hope have the 
rest of us got when we fit an aerial or try to help friends with advice?

"john m" <john@nospam.2net> wrote in message 
news:g2udcm$au0$1@news.albasani.net...
>
> "Bill Wright"  wrote in message 
> news:PfqdneGf5I90Fc_VnZ2dnUVZ8sTinZ2d@pipex.net...
>> Further to the recent discusssion about UHF TV aerials and their reputed 
>> performance, I can report that this morning I received through the post a 
>> flier advertising the Wolsey QR12 WF aerial. The gain is quoted as 
>> "14dB". There is also a graph showing the gain against UHF channels. Not 
>> so close examination shows that the gain only equals or exceeds 14dB on 
>> channels 65 to 69 incl. On channel 21 it is 7dB; on channel 33 it is 8dB, 
>> and on channel 52 it is 10.5dB.
>>
>> Bill
>>
> You should know by now that gain figures are meaningless.
A rather irritating way to put it. Try to make your points in a less 
patronising way.

Bill

In article <g2udcm$au0$1@news.albasani.net>, john m <john@nospam.2net>
wrote:

> "Bill Wright"  wrote in message
> news:PfqdneGf5I90Fc_VnZ2dnUVZ8sTinZ2d@pipex.net...
> > Further to the recent discusssion about UHF TV aerials and their
> > reputed performance, I can report that this morning I received through
> > the post a flier advertising the Wolsey QR12 WF aerial. The gain is
> > quoted as "14dB". There is also a graph showing the gain against UHF
> > channels. Not so close examination shows that the gain only equals or
> > exceeds 14dB on channels 65 to 69 incl. On channel 21 it is 7dB; on
> > channel 33 it is 8dB, and on channel 52 it is 10.5dB.
> >
> > Bill
> >
> You should know by now that gain figures are meaningless.  Around the
> days of CB the figures were plucked from the air to sell a product. 
> People quoted various wild claims for performance.  None of which were
> true. Unfortunately the same people must have grown up and gone in to TV
> aerial manufcturing.  How often do you see a 10 element aerial advertised
> as 40 elements if in an "X" shape. 

and that has been with us since the beginning of uhf in this country.  
eg J-Beam MBM46

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

"Doctor D"  wrote in message 
news:PumdnVrP8P-kSs_VnZ2dnUVZ8v6dnZ2d@posted.plusnet...
> That line of thought worries me immensely. Without the benchmarking, what 
> have we got to refer to?
>
> Most of the regular posters on this group are technically literate people 
> who, through work or hobbies know their way around a TV installation. 
> However beside Justin from ATV who tests everything in a madcap test lab 
> on top of a Yorkshire hill, and Bill, Carpy and Glenn who can make 
> meaningful comparisons on rooftops from the stock in their vans, what hope 
> have the rest of us got when we fit an aerial or try to help friends with 
> advice?

None really. But isn't it the same with virtually all consumer goods? The 
surprising thing about TV aerials is that they are a comparatively simple 
product, yet the manufacturers still seem to come up with some real 
abominations.

Bill

charles wrote:

> and that has been with us since the beginning of uhf in this country.  
> eg J-Beam MBM46

Indeed, but at least there's some logic in counting each X-director as 
four and, AFAIR, J-Beam only counted the driven element and reflector as 
one each.  Now manufacturers tend to count each part of a reflector 
assembly separately and I know of cases where the boom and even 
individual screws and rivets have been included in the element count!

-- 
Andy

"Andy Wade"  wrote in message 
news:6bi4r9F3c3ua5U1@mid.individual.net...
> charles wrote:
>
>> and that has been with us since the beginning of uhf in this country.  eg 
>> J-Beam MBM46
>
> Indeed, but at least there's some logic in counting each X-director as 
> four and, AFAIR, J-Beam only counted the driven element and reflector as 
> one each.  Now manufacturers tend to count each part of a reflector 
> assembly separately and I know of cases where the boom and even individual 
> screws and rivets have been included in the element count!
>

An example being the Triax super-gain, which adds together 11 elements, the 
dipole and the six elements on the reflector to classify it as an 18 element 
aerial.

> -- 
> Andy

In article , Bill Wright
 wrote:

> "Doctor D"  wrote in message
> news:PumdnVrP8P-kSs_VnZ2dnUVZ8v6dnZ2d@posted.plusnet...
> > That line of thought worries me immensely. Without the benchmarking,
> > what have we got to refer to?

[snip]

> > what hope have the rest of us got when we fit an
> > aerial or try to help friends with advice?

> None really. But isn't it the same with virtually all consumer goods?

Varies. In some cases people do give data that can be checked, and means
something. But in other cases they either give no data, or give values that
seem to the innocent to mean something - but are actually too vague to be
useful.

Looks like 'antenna gain'  and 'number of elements' are so vague in the
area as to be worthless.

> The surprising thing about TV aerials is that they are a comparatively
> simple product, yet the manufacturers still seem to come up with some
> real abominations.

I wonder if those who make antenna actually know much about *antennas*. Or
if they simply rely upon knowing how to make up a set of bits that can be
put together and act as an antenna. Then just copy familiar physical
designs, altering some details to make the result look different or be
easier to make.

If there is a 'benchmark' from some trade body, presumably it *should*
specify the frequency ranges, reference (i or d), etc. Not just accept a
'gain' at some unspecified spot frequency in some undefined conditions of
use. Ditto for clearly defining what can be counted as an 'element'.

I can recall Trevor Butler arguing in Hi Fi News many years ago that
some of the claims made for VHF radio antennas were clearly nonsense,
just from looking at the number of actual elements and the length of
the antennas. Yet the same old claims kept appearing in adverts...

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

On Fri, 13 Jun 2008 15:49:10 +0100, "Bill Wright"
 wrote:

>Further to the recent discusssion about UHF TV aerials and their reputed 
>performance, I can report that this morning I received through the post a 
>flier advertising the Wolsey QR12 WF aerial. The gain is quoted as "14dB". 
>There is also a graph showing the gain against UHF channels. Not so close 
>examination shows that the gain only equals or exceeds 14dB on channels 65 
>to 69 incl. On channel 21 it is 7dB; on channel 33 it is 8dB, and on channel 
>52 it is 10.5dB.
>
>Bill 
>

Sorry to interfere in your post, I did ask before in another post and
you did not see it, so I am taking it to the man.

I am buying a Promax Explorer. The basic one is about £1500 but does
not do DVB-S2, the Explorer II does, but is another £750.

I read somewhere you can get a good indication of HDTV signal quality,
by reading a adjacent, standard DVB channels quality. In your opinion
is that about right?

I visualise quite a bit of HDTV upgrade work coming my way with the
launch of HD on FreeSat, would I be doing myself a big dis-service by
saving the 750 quid?

In article ,
   Jim Lesurf  wrote:
>
> Looks like 'antenna gain'  and 'number of elements' are so vague in the
> area as to be worthless.

it was pointed out to me some years ago, by someone whose firm imported
German aerials, that in Germany their equivalent of the Trade Descriptions
Act applied to tv (or radio) aerials.  This seemed to 'policed' by the
aerial firms themselves - all of whom had proper aerial testing ranges.  If
firm A produced a new aerial, firm B would buy one & test it.  If if found
inaccurate gain figures, it would point out to firm A the error of their
ways and suggest the claims be amended - otherwise Trading Standards would
be involved.

Such a pity this doesn't happen here.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

"Jim Lesurf"  wrote in message 
news:4fafd6a085noise@audiomisc.co.uk...
> In article , Bill Wright
> I wonder if those who make antenna actually know much about *antennas*. Or
> if they simply rely upon knowing how to make up a set of bits that can be
> put together and act as an antenna. Then just copy familiar physical
> designs, altering some details to make the result look different or be
> easier to make.

In reality, in the case of the better manufacturers, a basic design is 
tweaked empirically and tweaked again until the results seem to be 
optimised. I think the difference between manufacturers is more to do with 
the effectiveness of the tweaks than in-depth theoretical knowledge, 
although of course a sound basis of theoretical knowledge is essential. The 
effectiveness of the tweaks would depend on the intuition of the tweaker, 
the ability to set up a valid experiment, the quality and appropriateness of 
the equipment and how well it was used.

Of course, there is not just one factor -- how well the aerial works -- to 
consider, there is another factor -- whether it looks good so that it will 
fool the uninitiated into buying it. To the uninitiated I have just one 
message: how many fancy and flowery aerial designs do you see in use by the 
professionals -- the broadcasters?

I envisage a scene in which the techys have produced an aerial design with 
good gain and directivity. It is small and light and passes the mV/kilo test 
with flying colours. They show it to the marketing department, who are 
palpably dismayed. "It's not much to look at, is it?"
"Err no, but it works really well!"
"OK, so well done chaps. But could you, err, add a little something? How 
about a full wave dipole?"
"We tried that and it didn't improve the performance at all, but it added to 
the weight and windage."
"OK. How about a really massive reflector?"
"Tried it. Same result."
"OK. Let's paint all the elements different colours and put go-faster 
stripes along the boom."

 Bill

"Anti-Spam"  wrote in message 
news:eu9a549v6sm8g8rfdhqms0aa0gclub94f4@4ax.com...
> On Fri, 13 Jun 2008 15:49:10 +0100, "Bill Wright"
> Sorry to interfere in your post, I did ask before in another post and
> you did not see it, so I am taking it to the man.
>
> I am buying a Promax Explorer. The basic one is about £1500 but does
> not do DVB-S2, the Explorer II does, but is another £750.
>
> I read somewhere you can get a good indication of HDTV signal quality,
> by reading a adjacent, standard DVB channels quality. In your opinion
> is that about right?
>
> I visualise quite a bit of HDTV upgrade work coming my way with the
> launch of HD on FreeSat, would I be doing myself a big dis-service by
> saving the 750 quid?

That's a tough one. I wouldn't rely on reading one mux in order to judge its 
neighbour though. As a general comment, over the years I've frightened 
myself many times by spending money on test equipment that seemed a bit over 
the top. Not once have I come to regret the purchase.

Bill

In article , charles
 wrote:
> In article , Jim Lesurf
>     wrote:
> >
> > Looks like 'antenna gain'  and 'number of elements' are so vague in
> > the area as to be worthless.

> it was pointed out to me some years ago, by someone whose firm imported
> German aerials, that in Germany their equivalent of the Trade
> Descriptions Act applied to tv (or radio) aerials.  

Our own TD and Sale of Goods acts probably apply. But I suppose the problem
is that the specification stated is so vague and sweeping.

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

In article ,
   Jim Lesurf  wrote:
> In article , charles
>  wrote:
> > In article , Jim Lesurf
> >     wrote:
> > >
> > > Looks like 'antenna gain'  and 'number of elements' are so vague in
> > > the area as to be worthless.

> > it was pointed out to me some years ago, by someone whose firm imported
> > German aerials, that in Germany their equivalent of the Trade
> > Descriptions Act applied to tv (or radio) aerials.  

> Our own TD and Sale of Goods acts probably apply. But I suppose the
> problem is that the specification stated is so vague and sweeping.

more likely finding someone capable of doing the testing. Even BBC R&D
haven't got an aerial range anymore.  The land was sold off. (accountants
rule).

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

In article , charles
 wrote:
> In article , Jim Lesurf
>     wrote:
> > In article , charles
> >  wrote:
> > > In article , Jim Lesurf
> > >     wrote:
> > > >
> > > > Looks like 'antenna gain'  and 'number of elements' are so vague
> > > > in the area as to be worthless.

> > > it was pointed out to me some years ago, by someone whose firm
> > > imported German aerials, that in Germany their equivalent of the
> > > Trade Descriptions Act applied to tv (or radio) aerials.  

> > Our own TD and Sale of Goods acts probably apply. But I suppose the
> > problem is that the specification stated is so vague and sweeping.

> more likely finding someone capable of doing the testing. Even BBC R&D
> haven't got an aerial range anymore.  The land was sold off.
> (accountants rule).

Is there a trade or consumer mag that should be doing measurements for
this?

Looks to me like another example of a general rule. That as soon as no-one
is checking a performance parameter for a consumer product, then some
makers promptly either stop quoting any values, or make them up. Darkness
then covers the details ...

Slainte,

Jim

-- 
Change 'noise' to 'jcgl' if you wish to email me.
Electronics  http://www.st-and.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
Armstrong Audio  http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc  http://www.audiomisc.co.uk/index.html

Thanks Bill, I will do the right thing, and spend the money.

>> Sorry to interfere in your post, I did ask before in another post and
>> you did not see it, so I am taking it to the man.
>>
>> I am buying a Promax Explorer. The basic one is about £1500 but does
>> not do DVB-S2, the Explorer II does, but is another £750.
>>
>> I read somewhere you can get a good indication of HDTV signal quality,
>> by reading a adjacent, standard DVB channels quality. In your opinion
>> is that about right?
>>
>> I visualise quite a bit of HDTV upgrade work coming my way with the
>> launch of HD on FreeSat, would I be doing myself a big dis-service by
>> saving the 750 quid?
>
>That's a tough one. I wouldn't rely on reading one mux in order to judge its 
>neighbour though. As a general comment, over the years I've frightened 
>myself many times by spending money on test equipment that seemed a bit over 
>the top. Not once have I come to regret the purchase.
>
>Bill 
>

"Anti-Spam"  wrote in message 
news:lg4g541kreip52579aa5e8ihqovssear5l@4ax.com...
> Thanks Bill, I will do the right thing, and spend the money.

That's the spirit. It all comes off the tax anyway.

Bill