Which lnb for my dish?

sreser

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I am trying to set up a system (on the cheap!) for the very first time. I have a TM 5200 USB, and a Fortec star HH90 motor from Maplins. My problem is I have scrounged a dish off my brother he wasnt using. Its old but in excellent nick. It is 90 cm wide and has Fuba Sat witten on the dish. The bracket that holds the LNB has a small aperture of only 2.8 cm or 11/8 inches in old money. I have bought a lnb from my local Maplins but its too fat for the dish bracket. Is there such a thing as a slim lnb that would fit my small bracket?

Secondly I have set a scaffold pole (vertically true!!) into the the ground at the top of the garden, with the wifes permission!! and will mount the dish on the pole. It is about 65 metres from my TM 5200. For this dist do I need special cable or will any do?

Thanks in hope of your help
 

satelliteman

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Welcome to satellites,

You might be able to purchase a new LNb holder for your dish with a 40mm collar OR change the dish :D

65Mtrs of quality coaxial cable will have a loss of 20dB @ 2150Mhz (top of 'IF' band). You can install line pre-amp to compensate for such loss.

Example: Technically, we measure satellite signals in dBuV.
A 90cm dish on a strong satellite will receive approx 80dBuV. You will loose about 2dB through the motor and 2dB through connections.

80dB - 20 - 2 - 2 = 56dBuV

A receiver requires 52dB minimum so the conclusion is to fit a pre-amp esp... for weaker satellites.

Other good signal parameters are required for acceptable viewing like carrier to Noise and Bit Error ratio but for cable loss we looking at signal power dB

Just check Power Consumption of the receiver as it has to supply the motor, LNb and a pre-amp.

Benchmarked cabling such as wf100 is fine


Lots of info here :)

Satman :)
 

Robbo

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Hi,

Yes I think you are going to need a "Universal Offset feedhorn" and a C120 LNB. It doesn't work out very cheap though.I think I would try and bodge something first, by making/finding a new holder. You may be able to buy a single holder online from somewhere, or try a 1"1/2 plumbing waste pipe clip.

Another option apart from an amplifier, would be to use better specified cable, such as wf165, the attenuation for this is only 20.9dB per 100 metre compared to 32.5 for wf100.


Following on from satmans calcs:-

80-13.5-2 -2 =62.5 dBuV, a bit more of a margin for you.:)


Or in other words, the attenuation of 65m of wf100 is approx equal to 40m of wf100, which you should be able to get away with.
Robbo:)
 

sreser

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thanx guys you have given me some great ideas. I will have a bash and let you know
 
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