picking up BBC with 2.4 metre dish

bodge

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#1
I picked up this second hand 2.4 m dish and want to be able to use it to pick up the BBC abroad. What changes need to be made to the LNB / feedhorn to make this possible ?
 

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Channel Hopper

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#2
A complete change of front end (its a C band voltage switching device and feed)

Measuring up a feed for good performance at Ku band will require some details on the excat diameter and depth of the reflector. - depth over diameter will give a figure somewhere between 0.3 and 0.4

Once you have this figure the most appropriate feed design in C120 configuration will match for the best efficiency.
 

Marts

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#3
2.4 metre :eek: hope it ain't too windy there ;)

Regards - jealous Marts O-Ha
 

steffan_st

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#4
Hey Bodge!

Dish looks good,don't forget to wash and wax it!
 

gameboy

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#5
bodge said:
want to be able to use it to pick up the BBC abroad
Where abroad? - have you checked the footprint for the dish size?
 

bodge

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#6
Hi Channel Hopper


I really appreciate your help but as I know very little about this kind of thing so I'm not quite sure what you mean . Sorry to be so stupid !!

Channel Hopper said:
A complete change of front end (its a C band voltage switching device and feed)

Measuring up a feed for good performance at Ku band will require some details on the excat diameter and depth of the reflector. - depth over diameter will give a figure somewhere between 0.3 and 0.4

Once you have this figure the most appropriate feed design in C120 configuration will match for the best efficiency.
 

Analoguesat

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#7
Bodge - where are you located? We cant tell you if you will get the BBC without this information - "abroad" covers a lot of ground!
 

bodge

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#8
I live in Sweden and am already picking up the BBC on my 1.8m dish. The reason for the 2.4 is that i want to eliminate problems due to heavy rain etc.
Analoguesat said:
Bodge - where are you located? We cant tell you if you will get the BBC without this information - "abroad" covers a lot of ground!
 

Channel Hopper

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#9
Then it should work as it has about twice the area, if the efficiency remains the same

Rain fade is usuallty 2db or about 40% of the loss
 

bodge

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#10
Could you explain for me in simple terms what I have to do to adapt this dish so I can use a c120 LNB.
Channel Hopper said:
Then it should work as it has about twice the area, if the efficiency remains the same

Rain fade is usuallty 2db or about 40% of the loss
 

Channel Hopper

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#11
Get out a tape measure
 

bodge

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#12
Sorry once again to ask such very basic questions- I take it you mean the diameter of the dish and the depth from the centre of the dish to the existing LNB . The later is difficult to measure at present because I had to take the tripod legs holding the LNB off to enable transport.



Channel Hopper said:
Get out a tape measure
 

bodge

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#13
Once I've taken all the correct measurements would I be right in thinking that I need to build a C120 flange holder to hold this feedhorn I have on my 1.8m dish or is an alternative feedhorn design necessary with this bigger dish ? Could I build a holder from the existing C band LNB holder ?
 

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Channel Hopper

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#14
You need the depth of the dish , from rim down to the surface of the reflector at its deepest point to work out the exact f/d ratio and the proper focal point. Unless you get this figure, you will not get a performing dish.

Other factors come in to it as well, how well the dish is made and how true the reflector surface is all round, moreso by a factor of three for Ku band, not much you can do if its off.

You should not be thinking of using anything you already have for the new front end.
 

bodge

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#15
Thanks Channel Hopper. One more question; does it matter which C120 flange feedhorn I use ? Does the size of the dish make any difference ?
Channel Hopper said:
You need the depth of the dish , from rim down to the surface of the reflector at its deepest point to work out the exact f/d ratio and the proper focal point. Unless you get this figure, you will not get a performing dish.

Other factors come in to it as well, how well the dish is made and how true the reflector surface is all round, moreso by a factor of three for Ku band, not much you can do if its off.

You should not be thinking of using anything you already have for the new front end.
 

Channel Hopper

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#16
bodge said:
Thanks Channel Hopper. One more question; does it matter which C120 flange feedhorn I use ? Does the size of the dish make any difference ?
I must be in a bagel wormhole toke
 
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