My C Band experiment on a SOD (Small Offset Dish)

[sonnetpete]

there are one or two other features of my recent setup that i dont quite understand - but i will start a new thread sometime , for those
as this thread is for "sonnetpete,s" setup .

Stout fellow, that's damned decent of you - especially when I seem to hijack everyone elses thread!!

 

[Vipersan]

Hi friends ..
sorry I've been absent for a few days ...
Picked up a virus and its made me quite ill ...but needed to post as there seems quite a bit of despondacy around atm ..

Ok ...

A couple of key points when getting into Cband and fitting an lnb for the first time ..

Cband LNB feeds are physically larger in diameter than ku lnbs ...so a bracket to mount it to an existing dish needs to be bought ..or manufactured to hold the lnb on the end of the lnb arm ..

Local oscillator frequency is 5150 ...
If you cannot set this in your set top box ...then you have to perform some calculations in order to obtain desired transponder frequencies...as the set top box cannot do this for you ..


To set up an lnb correctly you should first ignore circular ..and set up on a linear broadcast if possible ..
The demo'promo in Horizontal on Eutelsat5A @2.8 East is perfect for this ..
So ..no dielectric plate ...and adjust skew until this signal is at maximum ...
You then Have H & V correct ...as youve set up Horizontal ..
Now you can insert a plate ...and go for the circular polarised transmissions ...
These are _not_ skew dependent ...and the lnb postion can be as many degrees out skew-wise ..as you like ...
This is why you set up H/V first...

To get Left or Right you insert the plate into the grooves in the lnb throat ..
If you have 2 sets in the throat then a plate in either postion will either be Left or Right.
If you only have one set of grooves ..then this is why you set up H and V FIRST...as convention says we use Left = Horizontal and Right = Vertical ..
This can only be achieved on a one groove set lnb throat _IF_ you set linear correctly first.

Hope this helps a little ..
..and don't just give up ..
You'll need to become familiar with this sort of lnb(f) and how it works with respect to local osc frequency ...and polarisation ..If you're going to succeed with the Cband reception..
rgds
VS

 

[Huevos]

you mention that you had to lower. The side arms to accommodate the feed-horn

That is because he has Ku as the central LNB, then either side of the Ku LNB there is a C-band LNB, one for linear and one for circular. If you are just going to install a C-band LNB at the focal point you should be able to do it without any modification to the dish. Just make sure the centreline of the C-band LNB is in the same place the Ku band one was.

Have a look at my picture in post#28. This is probably pretty similar to Nelson's setup, except on his dish the side bars are a bit higher where they attach to the bottom LNB arm so they got in the way of the C-band feeds and so the side bars needed alteration.

 

[nelson_b]

Hi,


I have read the various posts relating to C-Band reception, thanks to ace, and others I have decided to join in, as I shall use my 1.8 C/M offset dish would the following bits of gear is suitable,
ESX241 C Band LNBF.
WSKU2C Kit Conical Scalar & Holder.
you mention that you had to lower. The side arms to accommodate the feed-horn are there any chance of a photo which would show what needs to be done, any other advice from the forum would be appreciated.


Joe01.

hi --
as "huevos " has said - it depends whether you just want C band - or if you want to keep k.u. and add C band ?
but either way requires some changes to the l.n.b. mount --
the way the channel master holds the bottom and side supports and holds the l,n,b - all in the one moulding piece, needs to be "replaced" by something that the -WSKU2C Kit- l.n.b. Holder can bolt onto and hold the bottom support arm in the correct position, so as to retain the centreline of the C-band LNB so that it is in the same place the Ku band one was. as huevos has also pointed out ,
i have some pictures of the various bracketing setups that i used before i settled on the K/u (central ) and C band either side arrangement that i have there now .
what arrangement did you have in mind ?

regards nelson.b.

 

[sonnetpete]

I'm sure they'll be fine, as they're almost identical to those that I bought. You will find there's a problem to solve as far as getting the LNB clamp mounted properly to your support legs. Not insurmountable but may require some ingenuity.

 

[nelson_b]

Hi,
]Thanks for your input and will follow all the good advice coming my way, are the items I mention in no forty-three be suitable for c-band only.
]joe01.

yes - the parts you have would be fine --

as sonnetpete said in his last post --
"getting the LNB clamp mounted properly to your support legs."-- is the tricky bit -- you will need to make something .

the fixing that i used on a 1.2 channel master - pictured in post -15 - of this thread, was no good for the 1.8 . i recall .

i will try to find some pics of the arrangement i made for a single C band l.n.b. and its holder for the 1.8 -- i dont have the pics on this p.c. - its quite a while ago that i did the central single C band on that dish -- i,l have a search for them later

cheers