"John Rumm" wrote in message
o.uk...
The Natural Philosopher wrote:
Arfa Daily wrote:
"The Natural Philosopher" wrote in message
...
Arfa Daily wrote:

I have a trunked distribution system in my house, that I put in some
years ago. It uses quality twin screen cable, and professional
amplifiers and tapper units. The analogue signals are nothing short of
perfect at every drop. The digital signals, however, are extremely
variable at various points. The situation was improved by replacing my
existing group 'A' aerial with a broadband type, but even so, when the
analogue transmissions in my area cease, I will probably have to give
the system a major rework, with new amplifiers etc, to achieve the
same level of 'goodness' of signal at each drop.

Even low quality wall sockets, can have a profound effect on digital
signals, that wasn't apparent on analogue ones. Don't believe all the
hype about how 'perfect' digital terrestrial signals are. They are
actually a lot less forgiving than you might think. It doesn't take an
awful lot to upset them, particularly whilst the power levels of the
transmitters carrying them, are still low ...



Well your experience is 100% opposite to mine. Digital terrestrial
through a distribution amp is perfectly as good as the analogue was.

If you have a decent amp, cable and socket quality is almost
irrelevant. If you have wired them up correctly of course,




But then perhaps I know what I am doing ;-)


Ah. I see. My almost 40 years in the trade says I don't then ...


Probably.

TNP in grumpy old git mode it seems!

Judging from Arfa's description of the system he has, that does not appear
to be likely in this case.

Fair enough. Do you know what a trunked distribution system is ?

Whether or not an existing system works (well) or not depends on many
things, including the antenna installation, any masthead preamps
involved, any combiners or diplexers involved, the quality of the cable
used for the drops to the various rooms, and that of the trunk cable if
it happens to be that sort of system, the age and quality of the
distribution or trunk driver amplifier, the quality of the wall sockets,
the quality of the tappers on a trunked system, and of course, how good
the digital signal is in the first place - both strength and quality, of
course.

Most analogue distribution systems did not need to broadband. Digital
ones do.

I take it you mean wideband? Most DTT installs will revert to grouped
operation after DSO - they have attempted to keep the number of non
grouped areas down to a minimum. In terms of channel bandwidth, the
spacing and bandwidth allocated is the same, although the DTT signal uses
the upper end of the channel more intensively than analogue.

But then I guess you know all that ... d;~}


Most distribution amplifiers are 'DC to light' anyway.

If you have installed a bunch of tuned stuff anywhere than at the
masthead then all that does is prove my point: You don't really
understand what you are doing.

Or the converse. "Difficult" installs that require pre distribution
filtering and levelling are rarely even attempted by non expert
installers. They are also difficult to conceive without proper test
equipment.

If you have not used correct buffered outputs that do not transfer faults
in one cable to another, it proves my point, you don't know what you are
doing.

Where did he say that? Did you get the bit about a trunked system with
taps?

If you cant correctly terminate a cable to a socket so you get
reflections and frequency dependent attenuation, it proves my point, you
don't know what you are doing.


The ONLY difference digital makes is that it uses a somewhat higher
bandwidth ..the only place that SHOULD be releavant is in any tuned
elements.

There are other differences as well. DTT is more succeptable to shot
noise, and ideally ought to have fully screened outlets, amps, connections
etc. Something that is not an issue for most analogue only distribution
systems.

The only place ther SHOULD be tuned elements, is the aerial itself, and
if it has one, a masthead amp. Possibly.

Again, this is an over simplification. Difficult locations and ones that
require multiple transmitter operation may quite often need filtering and
levelling. One may also require diplexers and other active components.
That is before you get to the issues of injecting other sources like CCTV
or door cams etc into a distribution system.

There should be NO tuned elements in the distribution system, if its

Other than where there should be that is...




--
Cheers,

John.


Quite. And yes, I did mean wideband. I've just got so used to saying
"broadband" in reference to the internet, that it accidentally slipped into
the sentence in this thread. And yes, my trunked system is quite complex, as
it carries analogue signals from two transmitters at opposite ends of the
band, as well as signals from a Sky box and a TiVo box and some CCTV as
well.

Arfa