Re: Dish


johnrigsec@...
 

In a message dated 05-11-03 10:53:41 GMT Standard Time, tdavid@dsl.pipex.com
writes:

Hi

I have one of RIGs 1mtr dishes with the coffee can on the end, can this be
used for the reception of MSG, and if so what other items are required? It
seems a waste to get rid of it only to replace it with a smaller dish

regards

Trevor
All,

Trevor's original e-mail and Ian's reply got me thinking.
Firstly of course, you should have been able to use a coffee can (1.69 GHz)
feed
with MSG-1 dissemination but owing to that satellite's inability to
disseminate, via
direct reception, imaging is being disseminated via the EUMETCast DVB service
on
Hot Bird-6 at 13 deg. east (at Ku-Band) [and you can't use a coffee can!].
1.69 GHz MSG direct dissemination may not happen till MSG-3 - at least - I
understand, the Ku-band EUMETCast service continuing till at least that time.

Now I know I should know this, having been operational in satellite TV since
the
early 80's, but am not sure.
I suspect someone out there will be able to give the definitive answer.

When I began receiving C-band satellite TV back in the early 80's followed by
Ku-Band reception, I used prime focus dishes and head end feeds and equipment
designed for prime focus dishes.

When DTH took off, the offset dish and LNB took over from prime focus.
Now, the offset dish is elliptical and the LNB (at the focal point) is below
the dish
pointing up into it.

Question.
Is the modern LNB specifically designed (geometrically) to work with an
(elliptical)
offset dish?
Or, can you also place it at the focal point of a prime focus dish?

You can successfully mount two (or even three) LNB's on a fixed offset dish
(spaced
on the LNB arm) of say 85 cm to receive satellites at various locations.
In my case, currently, Astra at 19.2 E and Hot Bird at 13 deg. E.
I tried dangling a Ku-band LNB - slightly offset in azimuth, next to the
coffee can feed
of my 1 m Meteosat-7 dish (pointed at 0 deg.) just as an experiment and was
able to receive Hot Bird (analogue) TV transmissions from 13 deg. E at the same
time,
noise free.

So, does anyone know about the design of the modern Universal Ku-Band LNB
feed geometry?

Regards,
John Tellick.
RIG.

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