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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

Freeview - Break up because of too strong a signal



 
 
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  #1  
Old July 20th 03, 09:41 PM posted to uk.tech.digital-tv
De
external usenet poster
 
Posts: 5
Default Freeview - Break up because of too strong a signal

Is it possible that I could get picture breakup because the signal is too
strong?

My aunt has lived in the same house for 3 years now and finally we decided
it was time to do something about her arwful TV reception and bring her into
the digital age with Freeview.

Anyway withthe standard antenna the signal was too weak - so we went in the
loft and changed it for a nice new 18 element antenna from Wickes and
instant improvement - when connected toa 1 metre cable to her TV - we didn't
even have to direct it - great picture everywhere.

Then we ran the cable down form the loft to the sitting room and the picture
was bad.

Andway next day we came back with a reel of Satelitte cable with the extra
layer of silver foil and the picture was instantly better then with the
normal Co-Axial cable.

Now her channels 1 to 5 are really good, and freeview channels all good
except the Sky Travel, Histroy and Sky news type channels.

Could the signal be too strong? Could the sue of satelittle cable instead of
normal coax be the problem?

We found if we added a signal booster the problems with freeview were even
worse.


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  #2  
Old July 21st 03, 09:48 AM posted to uk.tech.digital-tv
David Hearn
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Posts: 43
Default Freeview - Break up because of too strong a signal


"De" wrote in message
...
Is it possible that I could get picture breakup because the signal is too
strong?

snip

Could the signal be too strong? Could the sue of satelittle cable instead

of
normal coax be the problem?

We found if we added a signal booster the problems with freeview were even
worse.


From what I've been reading about aerial selection - you do need to make the
right choice for a high or low signal area. You shouldn't just use a
high-gain aerial regardless.

Low signal = high gain, very directional aerial to get the most signal as
possible.
High signal = low gain, less directional aerial. If you have a high gain
aerial in a high signal aerial, you may get too much signal - now, I don't
know what happens with too much signal - though I guess it may be down to
the design of boxes which may make some more or less prone to this problem.

You may have found that 1m of standard coax was so lossy that it made the
strong signal just fine - but the many metres of it made the signal too low.
Putting satelite coax in meant that you were getting the full (high) signal
right to the box - causing problems. Though I must admit I'm surprised that
normal coax is so poor that it would drop the strong signal to a 'normal'
one in just 1m when the signal is too high with many metres of satellite
coax.

Not sure if that's helpful for you.

D





  #3  
Old July 21st 03, 09:58 AM posted to uk.tech.digital-tv
Tony Walton
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Posts: 60
Default Freeview - Break up because of too strong a signal

De wrote:
Is it possible that I could get picture breakup because the signal is too
strong?


Yes. Too much signal can overload the input stages in your box, leading
to picture breakup. Try getting a couple of inline attenuators from an
aerial supplier - these plug into the aerial lead and reduce the signal.

--
Tony

  #4  
Old July 21st 03, 10:13 AM posted to uk.tech.digital-tv
De
external usenet poster
 
Posts: 5
Default Freeview - Break up because of too strong a signal


"David Hearn" wrote in message
...

"De" wrote in message
...
Is it possible that I could get picture breakup because the signal is

too
strong?

snip

Could the signal be too strong? Could the sue of satelittle cable

instead
of
normal coax be the problem?

We found if we added a signal booster the problems with freeview were

even
worse.


From what I've been reading about aerial selection - you do need to make

the
right choice for a high or low signal area. You shouldn't just use a
high-gain aerial regardless.

Low signal = high gain, very directional aerial to get the most signal as
possible.
High signal = low gain, less directional aerial. If you have a high gain
aerial in a high signal aerial, you may get too much signal - now, I don't
know what happens with too much signal - though I guess it may be down to
the design of boxes which may make some more or less prone to this

problem.

You may have found that 1m of standard coax was so lossy that it made the
strong signal just fine - but the many metres of it made the signal too

low.
Putting satelite coax in meant that you were getting the full (high)

signal
right to the box - causing problems. Though I must admit I'm surprised

that
normal coax is so poor that it would drop the strong signal to a 'normal'
one in just 1m when the signal is too high with many metres of satellite
coax.

Not sure if that's helpful for you.

D



Why is Satelitte wire so much better the Coax?

The differences were huge - with orignal Coax the signal was lousy then
replacing with the much thinner satelittle cable was so much better - if
someone was to rewire a house house is it better to use the satelitte cable
instead of coax into each bedroom from a master socket?

I know maplins do devices to cut down the signal strength from antennas -
was thinking this might help??


  #5  
Old July 21st 03, 10:23 AM posted to uk.tech.digital-tv
De
external usenet poster
 
Posts: 5
Default Freeview - Break up because of too strong a signal


"Tony Walton" wrote in message
...
De wrote:
Is it possible that I could get picture breakup because the signal is

too
strong?


Yes. Too much signal can overload the input stages in your box, leading
to picture breakup. Try getting a couple of inline attenuators from an
aerial supplier - these plug into the aerial lead and reduce the signal.

--
Tony



I see maplin do a 6db and 12db one for 5 is that an average price?

Also which do you think would be better? Is that going to make the analouge
channels look grainy?


  #6  
Old July 21st 03, 10:28 AM posted to uk.tech.digital-tv
De
external usenet poster
 
Posts: 5
Default Freeview - Break up because of too strong a signal


"Tony Walton" wrote in message
...
De wrote:
Is it possible that I could get picture breakup because the signal is

too
strong?


Yes. Too much signal can overload the input stages in your box, leading
to picture breakup. Try getting a couple of inline attenuators from an
aerial supplier - these plug into the aerial lead and reduce the signal.

--
Tony



The other option I just thought of was that the antenna came in two section
9 element on each segment - would removing the end segment help instead? to
halve it form an 18 element antenna to a 9?

by the way found a nice PDF document on TV reception

http://www1.jaycar.com.au/images_uploaded/tvrecept.pdf


  #7  
Old July 21st 03, 10:49 AM posted to uk.tech.digital-tv
Steve
external usenet poster
 
Posts: 6
Default Freeview - Break up because of too strong a signal

I just cant see that too much signal is the problem here.
You ave missed out some important information from your original post, ie
the location of your aunt (a postcode first four digits) would be useful,
and what about the transmitter, which one does she use? These are important
factors here.

Steve

"Steve" wrote in message
...
Yes, removing some elements will reduce the gain of the aerial and thus
reduce the signal. There are many ways of attenuating a signal, its

quite
easy to do.
"De" wrote in message
...

"Tony Walton" wrote in message
...
De wrote:
Is it possible that I could get picture breakup because the signal

is
too
strong?

Yes. Too much signal can overload the input stages in your box,

leading
to picture breakup. Try getting a couple of inline attenuators from

an
aerial supplier - these plug into the aerial lead and reduce the

signal.

--
Tony



The other option I just thought of was that the antenna came in two

section
9 element on each segment - would removing the end segment help instead?

to
halve it form an 18 element antenna to a 9?

by the way found a nice PDF document on TV reception

http://www1.jaycar.com.au/images_uploaded/tvrecept.pdf






  #8  
Old July 21st 03, 11:01 AM posted to uk.tech.digital-tv
Carl Hender
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Posts: 3
Default Freeview - Break up because of too strong a signal

Hi

I had to had a splitter/amp installed but the signal was so strong to one
side an attenuator had to be fitted aswell. So yes, too much signal strength
is just as bad as too little

De wrote:
Is it possible that I could get picture breakup because the signal is
too strong?


--
--
Bye, Carl
http://www.hender.co.uk/




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  #9  
Old July 21st 03, 04:54 PM posted to uk.tech.digital-tv
De
external usenet poster
 
Posts: 5
Default Freeview - Break up because of too strong a signal


"Steve" wrote in message
...
I just cant see that too much signal is the problem here.
You ave missed out some important information from your original post, ie
the location of your aunt (a postcode first four digits) would be useful,
and what about the transmitter, which one does she use? These are

important
factors here.

Steve


Well she lives in South Harrow not sure what the PostCode is HA something

The box says the transmitter is Crystal Palace.

She lives opposite a huge Park in South Harrow - so directly opposite her
are about 5 big trees but apart from that it's a lot of open space which I
assume was the reason she got a pretty good signal with just a set top
indoor antenna, only trouble was the exact positioning needed for the indoor
antenna.

She's orignaly called a company that fits TV antenna's and they said she'd
never get a decent signal due to the trees infront of her house, then I came
with an indoor antenna and got a perfect Analouge picture on all 5 channels.
After that we went to wickes and bought their 18 element Antenna.

... So do I take it the more elements you have on an antenna the more
accurate you have to be when you direct it? If she lived in a strong signal
area which I thing she does would a 10 element antenna have been better and
easier to setup?

Oh just of of interest her old TV antenna turned out ot be a huge VHF one
not a UHF - guess that explains why the TV Picture was so bad fo rthe last 2
years!! Don't know why she waited so long to ask us to look at it.

Oh Also I should say before witht he old COAX cable installed there was
evidence on the screen of the TV picking up Radio waves - but after
replacing tis with the Sat Cable it virtually all disappeared.



  #10  
Old July 21st 03, 07:59 PM posted to uk.tech.digital-tv
Stuart
external usenet poster
 
Posts: 142
Default Freeview - Break up because of too strong a signal


"De" wrote in message
...

"Steve" wrote in message
...
I just cant see that too much signal is the problem here.
You ave missed out some important information from your original post,

ie
the location of your aunt (a postcode first four digits) would be

useful,
and what about the transmitter, which one does she use? These are

important
factors here.

Steve


Well she lives in South Harrow not sure what the PostCode is HA something

The box says the transmitter is Crystal Palace.


Ahem - our aerial points UP at CP with fairly new coax. We are about 1000
yds from the transmitter with a internal roof aerial. Either I don't have
the elevation right ;-) or it is impossible to overload a Pace DVTA.

Work out how much less signal your aunt is getting than me...

--
Stuart


 




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