Offset dish recommendation for C-band?

sharp

Hello

I plan to experiment with C-band reception on a motorized offset dish and need some advise regarding needed equipment.

First of all what dish best suite the purpose Gibertini or Triax? I choose these ones because they are easier to get in my location.

N.B.
I have red the excelent tread about the same topic but could not find answer on my particular situation. sorry for that.

nelson_b

hi - sharp

what size of dish were you thinking of ?

i,v been experimenting with C band on a 1.8 offset andrews/ channel master recently -- with quite good results --

i would say - use a C band only l.n.b -- (mine,s just a cheap one from china )

and not one of the combined C /KU ones -- the one i tried did work -- but was dissapointing especialy the k/u side

it will need a conical feed for an offset dish --
and a dielectric plate for the circular polarised transponders that we can see -on almost all the sats here -- or from europe

regards - nelson.b

sharp

Thanks nelson_b!

I think about 1m Gibertini or Triax. Idealy I would like to have a C/KU combined LNB but can start with a C-band LNB only. Where can I find such a conical feed? Is it something like attached picture? Can you recommend some supplyer for all these things, LNB and accessories?
From another thread here I understood that C-band LNB need some special stuff to put in the dish holder. Do I need this conical feed for this purpose? What do you think about dishes I mention here?
Do not commercial C-band LNBs for circular polarization exist? That is my primary focus, Express on 40est, Yamal on 49est and ABS1 on75est.

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BombedOne

Each ofset dish needs specific conical feedhorn for C band.

SO I'd reccomend you to get primefocus dish for C band.

sharp

Unfortunatly I cannot install a primefocus dish because of legal restrictions here.

nelson_b

hi - can you go larger than 1 metre offset ? --- 1.2 or more would be better
as i think you will struggle to get the sats you mentioned , on 1 metre
looking at footprint maps your location should be quite a bit better than mine -- i can get some channels at Express on 40east, Yamal on 49east but the signal is low strength for me here in the u.k. on 1.8 offset

the l.n.b holder and conical feed look the same as the ones i have

i bought a DMX741U combination C and k.u. l.n.b. including dielectric plate and conical feed -- from america --
but the l.n.b is not practical for an offset dish in europe --
the feed in the k/u part is designed for prime focus - so will only pick up very strong satellites -- and the signal is weakened futher by needing the dielectric plate inserted in order to recieve C band L and R circular transponders --

i ended up buying a cheap C band only l.n.b from china -- and using the plate and feedhorn on that . with better c band results

the l.n.b holder was ok for holding either of the l.n.b,s--without being altered at all --

but it will not directly fit onto the arm of "any " dish only certain types -- here is a picture from WS website showing the type of dish arm setup that the holder fits onto

i had to make my own bracket arrangement to get the l.n.b. holder into the correct place on a andrews / channel master

the c band only l.n.b that i used can be found -- at Ebay-auction-site --- item number
310152529448

the other l.n.b. and bits an pieces came from -http://www.wsidigital.com/c-band_lnb_f.htm
delivery takes about a month - and i had to pay customs / V.A. T.
charges also

regards nelson.b

sharp

Thanks for all your help nelson.b. Reading all links you provided I begin to get confused. Why for instance C-band LNB are made for prime focus dishes? Been more or less comfortable with KU-band I do not understand this. In my understanding LNB is LNB whatever dish is. If the signal is reflected on the head of LNB what is wrong with offset dish? Anyway I start some commercial activity. I bought C-band LNB from US and a C-band kit for Gibertini/Triax from Germany. Any opinions on that? See attachments.

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nelson_b

hi -
the l.n.b and holder look ok -- my l.n.b is a "pauxis" also

you will need a conical feed for your C band l.n.b on your your offset dish -- like or similar to the bue one in the picture in my other post
and a dielectric plate to put in the throat of the c band l.n.b for L or R circular transponders -- have you ordered these also ?

are you going to get 1 metre or a 1.2 metre dish or larger ?

i feel you will struggle to recieve signals on only 1 metre - it seems most C band signals are not very strong -- large dishes are normaly used

i cant realy explain why c band l.n.b,s are made for prime focus dishes , but traditionaly this seems to be the case .

fitting them to offset dishes is a more recent development and is more experimental --

but all my reasearch prior to recently trying out this method -- told me the same -- you have to have conical feed rings for a offset dish

and you use flat feed rings for prime focus ---

if not the signal reflected from the dish will not be read correctly
and potential signal strength will be lost ---

sorry i cant explain this better --
perhaps someone else here on the forum will ?

regards nelson.b

sharp

Thanks nelson.b for all your help! Now on is just to put it all together and begin the experiment. I cannot really put a larger dish here because of legal restrictions in my area. So it will be 1m dish. Still hope to get a god signal from at least 49 east.
Will report on result when ready.

nelson_b

ok -- best of luck --
yes - please let us know how it goes for you --
cheers nelson.b

Turok

Hello!
the bigest ofset dish,if i remeber right,comes from the polish dish manufactor mabo with 1,86 m!
there are other some other brands from the chech republik,if you need offset,that a realtifly cheap,around 200€ for the dish!
what is the dish size limit,that allowed to install in stockholm?
for cband kombi lnb,please check your pm!

Satcom1

1.2 m offset most popular for small c band motorized dish. h-h motor should be the biggest you can afford. WSI international has most of what you need.

C/KU lnbf's are "ok" for large c band dish but ku lnbf is at a different f/d then the c lnbf, so there is a big tradeoff on smaller dish.

I use seperate ku and c lnbf on my set up.

I like the Panorama 13K c lnbf, centered on the dish and a standard linear mounted to the right and a ku circular mounted to the left. So you set your motor to position c band on center and offset motor positions east or west for the two ku lnbf.

Any of the conical scalar rings will work just fine on your offset dish but consider makeing your own with better SQ.

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I am not a complete idiot, some parts are missing.

sharp

Turok

I live in a rented flat. We are restricted by our landloard to setup a dish. It can be installed only inside a balcony which is 2M x 1M large. We have a balcony above us. So 1m dish is a max I can allow me. Please check your pm.

Satcom1
Thanks for explanation about LNBs. I understand better now. The picture attached is just what I want to achieve at the end. I want to use my STAB HH100 motor.

Satcom1

Here are some Pics. of one example, however, this is on a 1.2 M Prime Focus dish.

I noticed that you have a 80 cm motorized dish, If you use the cone Scalar above you should get several C Band.

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I am not a complete idiot, some parts are missing.

sharp

Just wondered how difficult it is making the conical scalar rings by myself?
What material should I use? Tools needed? Maybe someone met any instructions about it on the web?

Satcom1

Easy to make-

I bought aluminum roof flashing at the hardware store. Roll 12' X 14" cost < $10.

Pair of scissors, super glue, tape, compass and ruler for tools.

This thing make the dish highly reactive. Without the cones no signal with lnbf peaked to other C band satellite. With cones.....BANG... the video jumps in at 66% SQ. It will tune your 80 cm dish up for good reception on C band. Tunning is critical. First tune your lnbf for best signal on strong satellite. Slip on the cones and slide in and out to tune the TP you most want, others will not be as strong.

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I am not a complete idiot, some parts are missing.

sharp

I am afraid I'm not that handy man as you satcom1. Thank you anyway, it gives some inspiration.

KR

sharp

First test without conical rings today was unsuccessful. The only c-band satellite I cans see during summer time (a tree hide all others of interest) seems to be a 40 degree east. I got quite strong signal with 0 quality. Got then that I need this famous dielectric plate to get circular polarization from this sat. Need advice as how to put it in my Pauxis LNB and also how LNB should be placed in the LNB holder, I mean the orientation. I do not understand what is up and what is down on this devise. Also the front of LNB, where it should be regarding the holder?

Thanks in advance!

nelson_b

hi -sharp-

there are some groove - lines - inside the barrel of the pauxis
- the plate slides into them

the orientation looks odd -- but is the best place -- see picture

position in the holder -- just where it gives best signal on your dish -- start central -- and try forward a bit -- try back a bit --
dish focus will vary on different dishes

regards nelson_b

p.s. i,m certain you will need a conical feed of some kind before the pauxis will work for you -- on a small offset dish -- regards

sharp

Thanks Nelson, will try again according to your advise!

greatguy112

satcom mentioned the panaoram 13k lnb, i have a 17k cheap lnb from Ebay , that looses signal during the evening on 37.5W, in fact i'm using 1.3M prime focus dish, i was getting 40% signal(until about 2 weeks ago) but now down to 35 % during the day still watchable, then drops in the evening to around 29 , where i cant see anything, i know i need a good lnb at least that will be stable, and thinking of getting the panorama 13K , but people are saying on this borad that theres a shift of about 20MHZ, is that true and what really does that mean?, if its just a matter of adding 20MHZ to the frequency then i can live with that

sharp

Still in a preparation phase, waiting for autumn. I have just bought this thing, see picture. It is quite heavy.
Does all C-band flanshe LNB will suite this thing?
Can I reuse the dielectric plate from this in my Pauxus?

KR

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nelson_b

hi - sharp -
your offset feedhorn is a little different to mine .

if it fits on the pauxis barrel ok it may work perfectly well as it is .
just give it a try and see --

i.v not seen one with the plate in the feed like that before - is the plate removeable - and will it fit in the pauxis barrel ?

there seems to be quite a bit of scope to experiment with C band feeds an dielectric plate variations as "Vipersan " did on his setup -- you can read about in another thread in the C band section of the forum

regards nelson.b