What are the 'UHF' channels in relation to digital channels
Paul Kearney
I've just installed my freeview box (Sony VTX-D500U). I'm in Thornton
Heath - couple of miles from Crystal Palace, so reception shouldn't be a
problem. I've gone through all the UHF channels (21-69) but only get a
signal from half a dozen of them, however I get good channel reception on
all but a few channels (ITV News/TV Travel/QVC/CH5 are bad - but I guess I'm
not missing much :-) ). Sometimes the ITV1/2 channels get flakey - but then
they are all fine again a short while later.
I don't know what to check on the aerial (in the loft - not on the roof) to
know it is good for digital reception, but I only bought it a few years
back - and we are only a couple miles away.
Also if anyone knows where I can get a remote that definitely works with
this receiver please let me know (I have been able to get some very basic
response from my Merlin programmable remote - but not everything).
Thanks in advance!
Paul
simtan
There are six multiplexes (Mux) each on one UHF channel.
Cystal Palace is as follows:
http://www.itc.org.uk/uk_television_sector/reception_advice/digital_trans_gu
ide/show_transmitter.asp?siteID=66
c25 Mux 1
c22 Mux 2
c32 Mux A
c28 Mux B
c34 Mux C
c29 Mux D
If you go here:
http://www.dtg.org.uk/retailer/dtt_channels.htm
It tells you what channels are on each Mux.
You are having trouble with the 2 muxs that are still 64QAM, the less robust
way of broadcasting that allows 33% more capacity. All the others are using
16QAM. It just means your signal level in the loft is close to marginal,
and the difference between 64QAM and 16QAM tips the balance, and also
perhaps you are getting slightly less signal on Mux A than Mux 1. If Mux 1
and A adopt 16QAM hopefully you will have no problems, but that isn't
finalised yet.
Simeon
Richard Watkinson
"simtan" <simtan...@cesmail.net> wrote:
Also bear in mind that that from Crystal Palace the analogue channels transmit at 1000kW while the 6 digital Muxes are only 10kW.
Roofing materials attenuate (reduce) the signal recieved so a loft aerial is always going to struggle but as yours seems to be on the borderline you could try replacing the aerial downlead with digital quality cable and check the aerial itself.
It may be that you have a relatively low gain aerial in your loft for analogue and getting a 'higher spec' upgrade could be the answer. See how many elements it has got. Also check which group it is. This is indicated by a coloured bung at either end of the main structure.
Group A c21 - 34 Red Group K c21 - 48 Grey
Group B c39 - 53 Yellow Group E c39 - 68 Brown
Group C/D c48 - 68 Green Group W c21 - 68 Black
Your channels fall in the range 22 - 34 so it should be A, K or W
Wider band aerials like W do not give quite as good a performance size for size as those designed for a narrower band of channels. Here in Sheffield I've no choice my channels range from 21 - 67 :-)
Richard
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David G. Bell
<atdcgu$12vejr$1...@ID-142206.news.dfncis.de>
simtan...@cesmail.net "simtan" wrote:
At only a couple of miles from Crystal Palace you should still be
getting plenty of signal. If you have a wall socket and a flylead from
that to the digibox, check if that flylead is damaged. A good-quality
lead is pretty inexpensive -- cheap leads using thin wire can lose a lot
of signal.
There's the same that can be checked for the fixed part of the lead,
from the aerial to wherever, but it might be best to get a competent
aerial installer to check. It is also possible that the signal levels
are a bit too high, which is another simple, cheap, fix. But the
simple, cheap, fixes can add up if you go the wrong way.
Check the manual -- the old OnDigital/ITVDigital boxes had some sort of
signal strength meter, but I don't know the Sony. It may not be
detailed in the manual anyway, so explore any menu system there might
be.
--
David G. Bell -- SF Fan, Filker, and Punslinger.
"Let me get this straight. You're the KGB's core AI, but you're afraid
of a copyright infringement lawsuit over your translator semiotics?"
From "Lobsters" by Charles Stross.
Dan Sylveste
"Paul Kearney" <pkea...@blue-chip.com> wrote in message
news:atda0l$jht$1...@venus.btinternet.com...
> Hi All,
>
> I've just installed my freeview box (Sony VTX-D500U). I'm in Thornton
> Heath - couple of miles from Crystal Palace, so reception shouldn't be a
> problem. I've gone through all the UHF channels (21-69) but only get a
> signal from half a dozen of them, however I get good channel reception on
> all but a few channels (ITV News/TV Travel/QVC/CH5 are bad - but I guess
I'm
> not missing much :-) ). Sometimes the ITV1/2 channels get flakey - but
then
> they are all fine again a short while later.
Hi,
"Sometimes the ITV1/2 channels get flakey - but then
> they are all fine again a short while later."
This all sounds very familiar, and I too only live a few miles away from my
local transmitter!. Like me your almost certainly using a wideband aerial.
All I can suggest is that you consider getting a Group A aerial fitted
outdoors.
Regards,
Dan.
http://www.wolfbane.com/cgi-bin/tvd.exe?MAP=661,936?450,746
Stephen
transmit at 1000kW while the 6 digital Muxes are only 10kW.
>
> Roofing materials attenuate (reduce) the signal recieved so a loft aerial
is always going to struggle but as yours seems to be on the borderline you
could try replacing the aerial downlead with digital quality cable and check
the aerial itself.
>
> It may be that you have a relatively low gain aerial in your loft for
analogue and getting a 'higher spec' upgrade could be the answer. See how
many elements it has got. Also check which group it is. This is indicated
by a coloured bung at either end of the main structure.
>
> Group A c21 - 34 Red Group K c21 - 48 Grey
> Group B c39 - 53 Yellow Group E c39 - 68 Brown
> Group C/D c48 - 68 Green Group W c21 - 68 Black
>
> Your channels fall in the range 22 - 34 so it should be A, K or W
>
> Wider band aerials like W do not give quite as good a performance size for
size as those designed for a narrower band of channels. Here in Sheffield
I've no choice my channels range from 21 - 67 :-)
>
> Richard
It sounds to me more like there is something wrong with the aerial, like a
break in the cable somewhere, or a disconnection inside the terminal box on
the aerial, or inside the plug at the bottom end. There really shouldn't be
a problem that close to Crystal Palace. I am 8 miles from Crystal Palace and
get perfect recpetion of all 6 multiplexes with a set top aerial, indoors,
on the wrong side of the building.
I think the figures they give for transmitter power are misleading. Digital
powers aren't anything like so low as they sound. If you have a spectrum
analyser, you can see that most of the width of a digital channel is at just
as high a level as most of the width of an analogue one. Although the peak
power for analogue is 1000kW, this means an average carrier power of 250kW,
and the power in the sideband, which is what actually carries the picture
information, is only about 20kW (because modulation is much less than 100%
and it is mainly "single sideband".)
The digital powers at Crystal Palace have recently been increased to 20kW,
but for digital the power quoted is already the same as the sideband power.
So the sideband power, which is what matters, is already as high for digital
as it is for analogue.
simtan
> It sounds to me more like there is something wrong with the aerial,
> like a break in the cable somewhere, or a disconnection inside the
> terminal box on the aerial, or inside the plug at the bottom end.
> There really shouldn't be a problem that close to Crystal Palace. I
> am 8 miles from Crystal Palace and get perfect recpetion of all 6
> multiplexes with a set top aerial, indoors, on the wrong side of the
> building. I think the figures they give for transmitter power are
> misleading. Digital powers aren't anything like so low as they sound.
> If you have a spectrum analyser, you can see that most of the width
> of a digital channel is at just as high a level as most of the width
> of an analogue one. Although the peak power for analogue is 1000kW,
> this means an average carrier power of 250kW, and the power in the
> sideband, which is what actually carries the picture information, is
> only about 20kW (because modulation is much less than 100% and it is
> mainly "single sideband".) The digital powers at Crystal Palace have
> recently been increased to 20kW, but for digital the power quoted is
> already the same as the sideband power. So the sideband power, which
> is what matters, is already as high for digital as it is for analogue.
Also the s/n ratio needed for noise free analogue is about 45dB, for Digital
it is nearer 26 dB, which is nearly 20 dB.
Simeon
Alan Smith
<d...@NOSPAM.com> writes
distance, it is possible to overload the tuner section and get similar
symptoms to a low strength signal. DTT boxes seem to be very prone to
this. I would certainly try this before going to the cost of a new
aerial.
--
Alan Smith
Paul Kearney
Thanks to all who responded - I've a little project now to do some testing
over Christmas!
I'll get a proper look at the existing aerial, try it with a simple set top
aerial and try an attenuator.
I do know my downleads from the loft are only 'aerial' grade and not sat
grade - as I installed them some time back :-(
Regards
Paul
>