3m dish fringe area

[denby]

Hi all

I live in fuerteventura half way up the island and I'm trying to receive both Setanta which is on Eurobird and BBC Scotland which is on Astra D I can get both during the day but one or the other breaks up by eight O'clock depending on which I focus on or trying to find a midpoint.

The dish is a 3M which would work in this area but the cable run is over a 100 metres long. I installed one amp, by the dish and still lost 10 percent signal. So I installed a thicker cable, a Spanish spec which uses different terms than our normal RG cable but the next step up would cost me 90 euros just for each connector never mind the cost of that cable itself. So I installed a second amp half way along and got a full signal but also drastically reduced the S/N ratio so I left the center one on and found an improvement over the one near the dish but still not enough.

The lnb is an invacom quad with feedhorn, the box itself is irrelevant as the signal just isn't strong enough. I've read about the LC1000 which it advertises as the most powerful LNB in the world, has anybody tried these or any alternatives.

Setting the dish is like tuning a steel drum and as good as I can get it has anyone any ideas?

 

[IRstuff]

Get a second antenna, or two smaller antennas?

TTFN

FAQ731-376

 

[denby]

Thats an option I'm considering the problem is I don't know what size as nobody here has a dish just to catch Setanta and Eurobird is coming in at only a slight percentage higher so installing another large dish is out of the question. If I can just squeeze another few percent from the system I have that would be perfect.

 

[IRstuff]

Well, you could point to either one and determine how much headroom you have and that'll tell you what the minimum antenna is needed for only one sat.

TTFN

FAQ731-376

 

[denby]

The dish would not be much smaller than the one I have. I was considering adding metal petals round the dish to extend it's size and have them overlapping armidillo style and bolted to each other. I would also then have to extend the LNB arms as the focal point would change, does anyone know of the distance required for a prime focus 3.8M? Has anyone here heard of this being tried or know anyone that has?

 

[Mycroft]

The focal point of a parabolic reflector can be calculated by squaring the radius and dividing this by 4 times the depth of the dish. accurately measure the dish depth at 3.8 meters and then divide 3.61 by the result

Because you are also trying to receive two different satellite services the beamwidth of the downlink IF's may vary resulting in necessary critical alignment. Are the birds transmitting in linear format? polarisation is also critical with low Eb/No reception

Let me know the downlink receiver frequencies and the longitude of the sats you are looking at and I will do the math for you

Mycroft