Freeview, the Wrekin

On 2/24/2011 7:53 PM, Woody wrote:
wrote in message
...



DSO at The Wrekin is 20th April. Unfortunately the new channels
spread across aerial groups A and B so you will need to get the
aerial changed to wideband. If you want to watch Freeview before
6th April you may have problems as channels currently in use go
right up to 57.

http://www.ukfree.tv/shutdowndetail.php?tx=SJ628082

Before I get flamed let me explain. Your existing group A aerial
will have a peak response in channels 21-34 and the response
(gain) will tail off above that. As the lower channels are lower
frequencies then there will be less loss in the cable so, with
the associated higher gain, you will get very strong signals for
some of the muxes and very weak ones from those 'out-of-band.
Note also that some of the muxes on the oob channels are also
lower power so you will be double disadvantaged. If you are not
careful you could end up with a signal overload on some channels
(and believe me, with DTTV you most certainly don't want that)
and even end up with pixelation/freeze frame on some of the
higher channels.

If you replace the aerial then I would suggest a log-aperiodic as
this have a much flatter wideband response, have a good
front-back ratio, and you can get them with a slightly rising
response which will help to overcome the additional cable losses
at the higher frequencies.

You should also consider replacing the entire downlead with a
copper foiled screened variety as the braid on the old 'brown'
stuff is vary loose and will leave the cable open to interference
pickup. Even with strong solid signals a radiated switch click or
similar picked up on the cable will at best cause pixelation, at
worst temporary loss of picture/sound - it depends how your TV
handles such issues.



Many thanks for that comprehensive reply Woody, I hadn't realised that
there were other issues beside mere Gain and rejection of rear signals,
and particularly your comments re Signal Overload on some channels is
worrying. In the light of the issues you have raised I am now
considering a log-aperiodic as you suggested, (maybe I shall fit it now
rather than patch up the old one) are there different types ( bands) of
these particular aerials or does the wideband nature cover all
frequencies? you mentioned a rising response at higher frequencies Which
aerials would do this? Can you recommend a specific make/ model?
Similarly with cable (copper foiled?) it would have a double screen
then presumably?

I live in a low pitch roofed bungalow so installation is not a problem
to me, and with line of sight to the Wrekin it's easy enough to line up
particularly with the info on this site which someone on this NG pointed
to earlier:
Mounting A Terrestrial TV Aerial In The UK - 3 Aerial Alignment
Calculator (with internet mapping).mht
Regards
Don

On 2/24/2011 2:47 PM, Bill Wright wrote:
Gary wrote:
On 24/02/2011 09:49, Terry Casey wrote:
In on Thu, 24 Feb 2011
04:37:54 +0000
wrote:
Is there an F-plug to coax connector gizmo that I can use that will
not
attenuate the signal substantially?

http://www.tvcables.co.uk/cgi-bin/tv...t-adapter.html




It seems to me that you want problems. If it was me, I would get the
TV, connect it to the aerial that is giving good results and see if
you have a problem.

Even if there are problems it will be with the muxes that are not in
Gp A, and altering the cable won't help that very much. Or do you mean
that the existing cable doesn't go to the TV location?

Bill
Yes Bill, the piece of cable that I have is too short to go all the way
to the Aerial on the roof, hence the need to splice it in the downlead
within the loft space.
However, having had further advice/info maybe I'll install the whole
shabang with a new aerial and downlead instead of fiddling about with
temporary solution.
Thanks
Don

On Thu, 24 Feb 2011 18:29:08 +0000, tony sayer wrote:

Don

If the cable is the right OD (my old brown cable is - with a bit of grunt)
you could cut it about a couple of feet from the end and use an F-to-F
adaptor to put in a bit more cable.
I was having trouble extending the cable by a yard as the co-ax connectors
were very sensitive to position and any slight change caused the picture to
break up. Going F-to-F has solved it and it has to last only until the new
aerial ist installed.

http://www.aerialsandtv.com/onlineca...ml#Fconnectors

Yes thanks for that, it looks like a good idea and will suffice until
the new broadband aerial plus cable goes in after they've finished
messing about in October if we're lucky
Don

Surely something wrong with the co-ax connectors in use there then?....

Yes! Even so, co-ax is easily misaligned/strained/deformed whereas F-type is
solid.
--
Peter.
The gods will stay away
whilst religions hold sway

"Donwill" wrote in message
...
On 2/24/2011 7:53 PM, Woody wrote:
wrote in message
...


DSO at The Wrekin is 20th April. Unfortunately the new
channels
spread across aerial groups A and B so you will need to get
the
aerial changed to wideband. If you want to watch Freeview
before
6th April you may have problems as channels currently in use
go
right up to 57.

http://www.ukfree.tv/shutdowndetail.php?tx=SJ628082

Before I get flamed let me explain. Your existing group A
aerial
will have a peak response in channels 21-34 and the response
(gain) will tail off above that. As the lower channels are
lower
frequencies then there will be less loss in the cable so, with
the associated higher gain, you will get very strong signals
for
some of the muxes and very weak ones from those 'out-of-band.
Note also that some of the muxes on the oob channels are also
lower power so you will be double disadvantaged. If you are
not
careful you could end up with a signal overload on some
channels
(and believe me, with DTTV you most certainly don't want that)
and even end up with pixelation/freeze frame on some of the
higher channels.

If you replace the aerial then I would suggest a log-aperiodic
as
this have a much flatter wideband response, have a good
front-back ratio, and you can get them with a slightly rising
response which will help to overcome the additional cable
losses
at the higher frequencies.

You should also consider replacing the entire downlead with a
copper foiled screened variety as the braid on the old 'brown'
stuff is vary loose and will leave the cable open to
interference
pickup. Even with strong solid signals a radiated switch click
or
similar picked up on the cable will at best cause pixelation,
at
worst temporary loss of picture/sound - it depends how your TV
handles such issues.



Many thanks for that comprehensive reply Woody, I hadn't
realised that there were other issues beside mere Gain and
rejection of rear signals, and particularly your comments re
Signal Overload on some channels is worrying. In the light of
the issues you have raised I am now considering a log-aperiodic
as you suggested, (maybe I shall fit it now rather than patch
up the old one) are there different types ( bands) of these
particular aerials or does the wideband nature cover all
frequencies? you mentioned a rising response at higher
frequencies Which aerials would do this? Can you recommend a
specific make/ model? Similarly with cable (copper foiled?) it
would have a double screen then presumably?

I live in a low pitch roofed bungalow so installation is not a
problem to me, and with line of sight to the Wrekin it's easy
enough to line up particularly with the info on this site which
someone on this NG pointed to earlier:
Mounting A Terrestrial TV Aerial In The UK - 3 Aerial
Alignment Calculator (with internet mapping).mht
Regards
Don




Sorry, minor mistake. The aerial that will give you the rising
response is an E-group. Typically about 4dB gain at Ch21 up to
12dB gain around Ch55.

The log periodic is much flatter. If The Wrekin is LOS and not
too far away that is the one I would go for. Try to get one that
has a ready fitted connector at the mounting end. I only found
out recently that with a L-P the cable should be fed back through
one of the tubes as so doing is part of the matching: if you get
one with a connector already fitted then the match is done for
you.


--
Woody

harrogate three at ntlworld dot com

The log periodic is much flatter. If The Wrekin is LOS and not
too far away that is the one I would go for. Try to get one that
has a ready fitted connector at the mounting end. I only found
out recently that with a L-P the cable should be fed back through
one of the tubes as so doing is part of the matching: if you get
one with a connector already fitted then the match is done for
you.


Odd!, Which make and model was that Woody?..
--
Tony Sayer

"tony sayer" wrote in message
news
The log periodic is much flatter. If The Wrekin is LOS and not
too far away that is the one I would go for. Try to get one
that
has a ready fitted connector at the mounting end. I only found
out recently that with a L-P the cable should be fed back
through
one of the tubes as so doing is part of the matching: if you
get
one with a connector already fitted then the match is done for
you.


Odd!, Which make and model was that Woody?..
--



Don't ask me where I saw it - I've been to sleep since then!

I must admit that I was a bit puzzled by the Physics - if indeed
Physics is involved - but nonetheless it was there in black and
white.

Perhaps William might have some thoughts - printable please Bill?



--
Woody

harrogate three at ntlworld dot com

Woody wrote:


If you replace the aerial then I would suggest a log-aperiodic as
this have a much flatter wideband response, have a good
front-back ratio, and you can get them with a slightly rising
response
What log periodic gives a slightly rising response?

Bill

Donwill wrote:

However, having had further advice/info maybe I'll install the whole
shabang with a new aerial and downlead instead of fiddling about with
temporary solution.
Thanks
Don

Yes, I think your short cut was a long cut!

Bill

Woody wrote:

Sorry, minor mistake. The aerial that will give you the rising
response is an E-group. Typically about 4dB gain at Ch21 up to
12dB gain around Ch55.

'ang on a minute! A Gp E covers 35 to 68. You mean a Gp K, which covers
21 to 48 and like the unicorn* is a mythological creature, much
discussed but never actually seen in the flesh. As for an aerial that
covers 21 to 55, as you suggest, that would have to be wideband.

The problem with wideband yagis is that because the gain is ****e at the
bottom end the directivity is as well. The performance re ghosting and
CCI is abysmal.

*the unicorn is a type of colinear omnidirectional vertically polarised
aerial used mostly for DAB reception on Vikings' integrated helmet
radios. The active elements are stacked inside a horn-shaped radome
(hence the name). In order to allow diversity reception the horn aerials
are usually deployed in pairs, one on each side of the helmet.

Bill

Woody wrote:
"tony sayer" wrote in message
news
The log periodic is much flatter. If The Wrekin is LOS and not
too far away that is the one I would go for. Try to get one
that
has a ready fitted connector at the mounting end. I only found
out recently that with a L-P the cable should be fed back
through
one of the tubes as so doing is part of the matching: if you
get
one with a connector already fitted then the match is done for
you.


Odd!, Which make and model was that Woody?..
--



Don't ask me where I saw it - I've been to sleep since then!

I must admit that I was a bit puzzled by the Physics - if indeed
Physics is involved - but nonetheless it was there in black and
white.

Perhaps William might have some thoughts - printable please Bill?



I think there's a lot of ******** talked about log periodics. By trial
and error designs have been found that work, then theorists have been
trying to prove that they do in fact work. In theory a bumble bee can't
fly, but it does.

Allah the Great has given us the log-periodic; we should not question
His wisdom. We should take the log periodic to our breasts and rejoice.

Bill