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Re: Terrestial Interference in Australia?

At 09:31 10.11.1996 GMT, you wrote:
>Dear Dr Dish,
>
>3 weeks ago, I had installed a dish/receiver setup to allow us to view the
>European Broadcasting Bouquet at 4000Mhz on AsiaSat-2 here in Australia.
>
>The equipment installed for me was:
>
>1.8m aluminium Paraclipse dish
>Panasat IRD520 receiver
>California Amplifier "Mini Mag Plus" LNB
>
>The problem is that apart from a few days early on, we have not been able
to get
>a reliable picture/sound. All 5 channels of the EBB constantly break up, go
>blank, lose sound. It is unwatchable, at all times of the day, there doesn't
>appear to be a pattern.
>
>After quite a few telephone calls to help us, the installer returned on Friday,
>and spent around 5 hours on the problem. He tried everything,
>switching LNB's, receivers different examples of my Panasat IRD520 as well as
>other different units (inc. analogue which apparently worked fine)
>
>Everything checked out fine with his meters. Apparently the signal strength is
>excellent, CNR is very good, etc etc.
>
>He's now concluded that the problem is caused by TI (terrestial interference)
>from a nearby airport, I have two of them, a small one 3 kms away and an
>International one (Tullamarine) 8km away. The last one is more likely to be the
>culprit. The IF (Intermediate Frequency) from the LNB to the receiver is
>apparently where the interference is happening. 5150Mhz (LNB freq) minus 4000
>Mhz (EBB on AsiaSat-2) equals 1150Mhz which is apparently approx. the frequency
>that radar uses at the airports.
>
>Do you have any personal experience with TI of this sort? Apparently it
>is quite rare in Australia but extremely common in Asia, especially places like
>Hong Kong.
>
>Do you think that it actually could be TI that is causing this? As somebody has
>suggested to me. I would have expected that radar interference from an airport
>would come and go as the radar swept around its 360 degree axis. ie.
approximate
>15 second intervals of interference.
>
>I felt sorry for the installer guy, he spent a lot of time running a lot of
>tests and he
>has acknowledged that it is a problem that is his responsibility to fix. He
>suggested we could try moving the dish, not easy as it is in a good spot in the
>backyard and well cemented in now, and it would be a matter of "hit and miss"
>finding a position to avoid the TI.
>
>We could also try some different "filters", which appears messy and a bit
>expensive I guess.
>
>He says the alternative is using a different receiver to the Panasat IRD520.
>Apparently this unit, apart from being very sensitive - which can be good -
does
>not have any built in TI filtering which the newer units do.
>
>One he is talking about is a unit called a DigiSkan. Have you heard of
>this unit? He tells me his company has been testing the unit for them to check
>its suitability for receiving the European Broadcasing Bouquet in Australia and
>apparently has functioned superbly. I've searched the Internet though but
>haven't been able to find a single reference to it. He has offered to let
me try
>one as soon as he has one available (next week) but we didn't speak as to any
>difference in price (I assume this DigiSkan is more expensive than the
Panasat).
>Anyway, he is going to fax me a whole stack of specs on the unit this week.
>
>What other digital Mpeg-2, DVB compliant receivers might anybody recommend for
>the purposes of receiving the EBB on AsiaSat-2 here in Australia?
>
>This is all a bit confusing to me. Any advice you might have to offer would
>be greatly appreciated!
>
>
>Thank you.
>
>= Tony =
Dr.Dish:
Soory, but this one took a little bit longer. I do not think it is
terrestrial interference. The IF of 1150 is mainly used a a airport beacon,
which could not do any harm on your signal. If you connnect a analogue
receiver to your dish and go to the same frequency (4.000 GHz) ther must be
strong interference, if T.I. is involved. I believe itīs the Panasat IRD
520, because I got several reports regarding the reception of the European
Bouquet. It is still a problem - even for the program provider Deutsche
Welle TV. Pace could produce a working unit, but still thinks in quantities
100.000 and moved the headquarter to the seventh heaven (and may fall down
in due time ...), but NOKIASīs Mediabox could do the job very reliable. So
far as I know there is allready a agreement between Deutsche Welle and
NOKIA.  For further development watch TELE-satellite magazine and our
partner magazine COOPīs TECHNOLOGY DIGEST from New Zealand.
---------------------------------------------------------
Dr.Dish (Christian Mass)
Editor of TELE-satellite magazine
Producer of drdish@tv, Europeīs first satellite info-channel
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