Will DAT 75 get to the bottom of poor reception on ITV/C4...?

Andy Wade wrote:
Mark Carver wrote:

According to my DTG pocket book the minimum signal level for reliable
DTT reception is 35 dBuV (again as delivered to the tuner) ?

It sounds as if you're looking at a rather early version of one of the
DTG R-books there Mark. The recommended figure was quickly revised
upwards by 10 dB in the light of practical experience of impulsive
interference.

You're quite right Andy, my book dates back to the last century :-)

I see the 2002 edition quotes 45dBuV, Page 7 he-

http://www.dtg.org.uk/publications/books/r_book2.pdf


If II wasn't a problem 30 dBuV would just about be OK, even for 64-QAM,
but in practice II break-ups don't seem to disappear until you're above
40 dBuV - or maybe 50 dBuV with a combination of poorly screened
downlead, isolated outlet plate and crap moulded flylead. Attending to
the latter two as well as the main downlead is quite important.

I get a couple of glitches a month on the 64QAM muxes at 55 dBuV


--
Mark
Please replace invalid and invalid with gmx and net to reply.

Thanks guys. Very helpful.

I looked at the DTVG guide, and it seems to suggst that my post-Viterbi
BER, even on ITV, is OK (they say 10 to minus 4 and i'm 10 to minus 5).

So...... I am wondering whether what i am suffering from is Impulsive
Interference?

Having said that, I HAVE got double screened cable, very good
connections etc., so i would be surprised.

Am reluctant to seek my installer to go DAT 75 vs the DAT 45 if we're
chasing the wrong issue?

Really appreciate your views... Thanks!

....snip...

As others have said, for CP use a group A. When I replaced my own aerial I
asked this NG lots of questions about various gains, sizes etc. and one
thing I learnt fast was just how poor a wideband aerial is compared to a
banded aerial. Now I've never needed to try one of Bill's stacks but the
theory certainly seems sound and nobody's ever said they don't work.

And just in case, beware of frankly useless aerial installers. The chimneys
around here are festooned with high gain widebands whereas my 18 element A
does a perfect job.

Paul DS.

In article . com,
wrote:
Thanks guys. Very helpful.

I looked at the DTVG guide, and it seems to suggst that my post-Viterbi
BER, even on ITV, is OK (they say 10 to minus 4 and i'm 10 to minus 5).

So...... I am wondering whether what i am suffering from is Impulsive
Interference?

Having said that, I HAVE got double screened cable, very good
connections etc., so i would be surprised.

Impulsive interference can get into the system in other ways.

Firstly straight into the aerial. Can the aerial 'see' a road? Passing
traffic, particlarly motorcycles can cause ignition inteference. High
sided and roofed vehicles can cause a momentary reflection from to get into
the aerial and casue cancellation of the direct signal.

Secondly through the mains wiring. Thermostaticaly controlled devices like
boilers or fridges can put a 'glitch' on the mains. Depending on the
quality of the power supply in your decoder, this may upset the unit.


I am concerned, from your original posting, that you are getting so much
signal from Reigate on your CP aerial. Perhaps you would do better with an
aerial aligned on Reigate.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

In article ,
Paul D.Smith wrote:
...snip...

As others have said, for CP use a group A. When I replaced my own aerial
I asked this NG lots of questions about various gains, sizes etc. and
one thing I learnt fast was just how poor a wideband aerial is compared
to a banded aerial. Now I've never needed to try one of Bill's stacks
but the theory certainly seems sound and nobody's ever said they don't
work.


They do work - if properly installed.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Mark Carver wrote:

I get a couple of glitches a month on the 64QAM muxes at 55 dBuV

Fairly acceptable, n'est ce pas? In any case a change to 8K and 7-10 dB
power increase in a few years time should sort that out ;-)

--
Andy

Andy Wade wrote:
Mark Carver wrote:

I get a couple of glitches a month on the 64QAM muxes at 55 dBuV

Fairly acceptable, n'est ce pas?

Yes, no problem at all.

In any case a change to 8K and 7-10 dB
power increase in a few years time should sort that out ;-)

Even more for me, living on a bearing that puts me on the falling edge
of Hannington's infamous 'Guildford Notch'. I'm 6-8 dB down on the max
lobe anyway, so roll on 2012 I say ! :-)

All, point noted re stepping away from wideband.

Before so doing, I am pretty sure that my DAT 45 does not have the MRD
(masthead amp) - so i have the choice of going for the DAT MRD
(downside - located on aerial and not adjustable) or adding a masthead
amp in the loft (advantage - variable and accessible).

Strikes me this should be an immediate course of action? Anyone
disagree?

Also, impulsive interference unlikley to be JUST on ITV group?

wrote:
All, point noted re stepping away from wideband.

Before so doing, I am pretty sure that my DAT 45 does not have the MRD
(masthead amp) - so i have the choice of going for the DAT MRD
(downside - located on aerial and not adjustable) or adding a masthead
amp in the loft (advantage - variable and accessible).

Strikes me this should be an immediate course of action? Anyone
disagree?

Also, impulsive interference unlikley to be JUST on ITV group?

There's another factor. If I understand correctly the ITV/4 mux from
both Reigate and CP are affected ? I note that they are on UHF Chs 21
and 22 respectively.

It's a long shot, but just below Ch 21 is the TETRA radio band, have a
read of Bill's article on the subject he-

http://www.wrightsaerials.tv/Tetra.htm

A further clue might be the presence of patterning on analogue ITV from
CP (UHF Ch 23)

Good point, which occured to me also. But i tried a TETRA filter/braid
breaker and it had no effect.