Andy Hall wrote:

On Thu, 18 Sep 2003 19:04:17 +0100, Dave Plowman
wrote:


In article ,
tony sayer wrote:

As a general comment, DAs for FM use are rarely satisfactory.


Have you any reasoning for that assertion Dave?..

Most good receivers approach the maximum theoretical sensitivity, so
adding untuned gain before them will do no good. Passive splitting works
just as well. You might get a VHF distribution system to work tolerably
well for clock radios on local reception, but that's about all.

Of course I could be wrong, but I've yet to actually witness for myself
one that does work as well as without.



Hmm. I don't seem to have any problems in that area.

I have a combined UHF and VHF distribution system as follows:

Feeds from two Televes wideband UHF antennas via Spaun front end
amplifiers each followed by channelising filters. There is another
feed from a set of IKUSI modulators followed by a channelised filter
to incorporate VCR, DVD, satellite and other feeds into the system.
These are combined via a splitter and then the signal from a 4-element
Triax for Band-II is brought in via a diplexer.

The combined signals then fed to an IKUSI CBS901 launch amplifier

http://www.teldis.com/CP-IKUSICBS.htm

This feeds a distribution system of multiple splitters with outlets
going to diplexer sockets - in some cases several per room.

The channelised filters are set to equalise the off-air TV signals as
well as the locally modulated ones. There is then a single gain
control on the launch amplifier to provide the correct UHF level at
the room outputs.

It works out from the design that there should be no uplift for the
Band-II signals - in fact IIRC there's a few dB.

At any rate, I have a variety of tuners of different quality levels
fed from the system. I've checked them on the distribution system as
well as directly from the antenna and there does not seem to be any
noticable difference. A couple of French transmitters come in a bit
better through the distribution system, although were pretty weak
signals beforehand.

Everything's cabled in proper CT100 and care taken with connectors
etc.



That is consistent with my experience also.

The one exception being truly naff 'alarm clock' radios,

which are SO bad that a bit of a boost improves them :-()




.andy

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