Anyone using a 2.7 m offset

frassle · 16-06-2003

The problem I am having with the 2.7 m offset is really down to the lnb. Using an Invacom 0.3 helps slightly but this is really designed for a 1.6m offset and doesn't do the job properly on this size of dish.
On a prime focus they work fine.
So I am trying to find an lnb more suited to the dish size.

longridge · 17-06-2003

Hi Frassle,
i am aware of this problem so when i spoke to invacom they told me that the feedhorn on the invacom lnbs(offset) are designed for dishes for up to 1.5m offset. I have given them all the specs for the 2.7m offset dish and both of them( Dish manufacturer and Invacom) are working now to send me a feedhorn that will work for those antennas. It will be a feedhorn that you will be using with a prime focus lnb(invacom) so it will pick up the missing frequencies.
I will let you know when those samples arrive to me and tested.

Best regards
longridge

mjs1006 · 23-10-2003

Hello Longridge,have you received and tested the new feedhorn(sample) for the specific 2.7m. offset dish?I have used a laminas 2.4 offset dish using a Sharp 0.4dB noise factor.I improved the gain by increasing the focal distance lenght by1.5cm and also 1cm above feed holder.

mjs1006 · 23-10-2003

has any one tested Supral,Prodelin,Andersen (2.4m offset) in Cyprus?Thankyou in advance.

**pipoo** · 25-10-2003

Originally Posted by longridge

Hi Frassle,
i am aware of this problem so when i spoke to invacom they told me that the feedhorn on the invacom lnbs(offset) are designed for dishes for up to 1.5m offset. I have given them all the specs for the 2.7m offset dish and both of them( Dish manufacturer and Invacom) are working now to send me a feedhorn that will work for those antennas. It will be a feedhorn that you will be using with a prime focus lnb(invacom) so it will pick up the missing frequencies.
I will let you know when those samples arrive to me and tested.

Best regards
longridge

Could you be more specific, longridge, please.I'm planning to put up the same dish any day now, so the feedhorn problem is very crucial to me.Does that mean that the prime focus invacom feedhorn would cover the most of the 2.7 m offset dish?Or are there some specific changes that have to be made by Invacom or the maker of the dish?
Best regards

***>COR<*** · 25-10-2003

Hi,

For maximum results every dish needs his dedicated feedhorn, complementary for the dish, thereby transferring the maximum energy in phase to the pickup probe of the lnb.

The universal lnbF's have been made for a variety of dishes to perform reasonably well with many brands and sizes of dishes.

Since most dishes go from 60 cm's to 1.2 metre, the feeds that are integrated are made compatible for these F/D's and perform well in them.

Going to "oversized" offset antenna's you have a different F/D and need a feed that makes use of the energy the dish points to the feed.

That is why for these dishes you mostly better can go for the feed that the maker of the dish has in stock for that dish, and go for the lnb C120 flange type to get the maximum out of the combination.

CHeers,

Cor.

http://www.chaparral.net/ts_feeds.html

A nice read up on this

mjs1006 · 27-10-2003

Originally Posted by frassle

The problem I am having with the 2.7 m offset is really down to the lnb. Using an Invacom 0.3 helps slightly but this is really designed for a 1.6m offset and doesn't do the job properly on this size of dish.
On a prime focus they work fine.
So I am trying to find an lnb more suited to the dish size.

Offset Invacom LNBs are suitable for offset dishes with a f/D ratio between 0.55-0.65(checked on Invacom website).The 2.7m. Offset dish by Laminas f/D is 0.609.Focal distance=1.5m. and minor diameter D=2.46m.Anyhow I will purchase a offset Laminas feedhorn to test with C120 flange LNB and come back with results.Thankyou,mjs1006

***Zorba*** · 27-10-2003

I didn't think feed horns for offset dishes had f/d ratios as the feedhorns are cone shape,even the c120 type.

Originally Posted by mjs1006

Offset Invacom LNBs are suitable for offset dishes with a f/D ratio between 0.55-0.65(checked on Invacom website).The 2.7m. Offset dish by Laminas f/D is 0.609.Focal distance=1.5m. and minor diameter D=2.46m.Anyhow I will purchase a offset Laminas feedhorn to test with C120 flange LNB and come back with results.Thankyou,mjs1006

**Channel Hopper** · 27-10-2003

Offset dishes are part of a cross section of a larger prime focus dish, they still have a focal point and so the f/d ratio remains valid

**pipoo** · 28-10-2003

Originally Posted by mjs1006

Offset Invacom LNBs are suitable for offset dishes with a f/D ratio between 0.55-0.65(checked on Invacom website).The 2.7m. Offset dish by Laminas f/D is 0.609.Focal distance=1.5m. and minor diameter D=2.46m.Anyhow I will purchase a offset Laminas feedhorn to test with C120 flange LNB and come back with results.Thankyou,mjs1006

Well, the thing is I didn't find any link on Laminas' web site advertising feedhorns suitable for their 2.7m offset dish.Is there some link or e-mail address to contact someone from Laminas directly?
Thanks in advance.

mjs1006 · 28-10-2003

Originally Posted by pipoo

Well, the thing is I didn't find any link on Laminas' web site advertising feedhorns suitable for their 2.7m offset dish.Is there some link or e-mail address to contact someone from Laminas directly?
Thanks in advance.

They have a feedhorn PO 40.It is on

www.laminas.com.pl/prom.htm).mjs1006

FRINGE · 2 Weeks Ago

This is an old thread but I am in the same situation as mjs1006. I have a 2.7m Laminas offset dish (but in Tenerife) and am considering a new quad LNB (Invacom C120 - QDH-031) with a Laminas PO-40 feed (which I think would be best) or a Channelmaster feed - the channelmaster was recommended to me by Invacom. So would very much like to know how mjs1006 got on with his test.

**Topper** · 2 Weeks Ago

Welcome to the forum FRINGE

I regret you are unlikely to receive any answer as that was the last post mjs1006 made some 5 1/2 years ago and he has not logged in since

FRINGE · 2 Weeks Ago

Many thanks for the warm welcome topper, it's good to be here.

Your comments re timescale and subsequent lack of posts are noted. I decided to go ahead with the Invacom C120 (QDF-031) LNB and Laminas feed horn anyway. Will start a new thread on the subject after the parts are received and tested here in Tenerife. I'm sure it will be of interest to others.

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