[opendtv] 34 km distance passive rabbit ears TNT reception OK
- From: Olivier Houot <olho_avatar_i@xxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 03 Nov 2005 01:51:05 +0100
As a short follow-up to my post regarding TNT (french DTV) reception in
Le Mans, i just wanted to add that i finally managed to obtain a pair of
old unamplified rabbit ears antenna that was gathering dust in my
father's basement due to poor results with analog reception.
I said i was 47 kms away by road from the transmitter, but checking with
a map reveals that , as the crow flies, the distance is only a little
more than 34 kms. The transmitter radiates 26 to 32 Kw of power
(depending on the multiplex) in an isotropic pattern
Due to the available cables and connectors at home, i had to connect the
antenna to the receiver through a 5m long supermarket coaxial cable. I
have put it on top of the TV set, the usual place for this kind of
device. My outdoor antenna is on top of a farm building, which it
therefore doesn't see as an obstacle , but my TV room is behind the
building, at ground level, so the signal has to cross through it to
reach the indoor antenna.
Surprisingly, there is a recognizable analog picture, but very snowy.
Going digital, i manage to pull in all the channels, 64QAM as well as
16QAM, but i need two different angles for that (and one of them doesn't
allow for a lot of error margin). Moving within 2 meters of the antenna
can trigger breakups on some channels.
Adding a 18 dB amplifier allows for single angle reception of all the
channels but i couldn't do as much testing as i wish under those
conditions due to poor mechanical match of the available connectors (the
antenna had somehow lost its original connector so i clipped on a quick
and dirty solderless type).
I was wondering if the wall plug carrying the signal from the outdoor
antenna could somehow leak some RF power into the room thereby helping
the indoor reception, but from what i remember of transmission lines, an
unterminated cable end would rather produce total reflection instead.
And covering the wall plug with a metallic can does not seem to make a
difference.
Anyway, i am rather pleased with the results, considering the modest
power (compared to US standards) of the local transmitter.
With the outdoor antenna, the occasional once-in-an-evening glitch i
observed during pre-launch phase seem to have disappeared. The picture
has been stable for weeks, even though the weather is now more rainy
(temperate climate rains only of course).
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