Upside down offset dish

[7mdish]

For the 2.4m CM from RimaNTSS's picture I'd come to f/D=0.60.

Opening angle of the CM-dish would be about 79.5 degrees (assumed inputs H/W/dcenter about 2630?/2425?/232.1, leading to BF=1460, AF=2471 and FG=1651 as indicated in the picture).
That 79.5 degree would be equivalent to a prime focus f/D-equivalent of 0.69.

Greetz,
A33

I have very few knowledge with these parameters and calculations.
I know a little bit about f/d ratio meaning, not much more.
But from your post it seems that this feed could match the dish. We will see and let you know. Thanks.

 

[RimaNTSS]

Common folks, do not disappoint @7mdish , the feed he has ordered designed for Prodelin 1184 series antenna. I had a couple of those some time ago. Prodelin 1184 has exactly the same opening angle as CM 2,4m antenna, namely 79 degrees ish. So, the feed should match the antenna perfectly.

 

[Channel Hopper]

Common folks, do not disappoint @7mdish , the feed he has ordered designed for Prodelin 1184 series antenna. I had a couple of those some time ago. Prodelin 1184 has exactly the same opening angle as CM 2,4m antenna, namely 79 degrees ish. So, the feed should match the antenna perfectly.

I wasn't attempting to disappoint, my knowledge of CM reflectors is they have excellent characteristics at both C and Ku band frequencies, though I have also seen ( and purchased ) their 0.8 f/d feeds, which have been offered since 2005/6.

I assume the 1.8 and 2.4 dual reflector versions allow compatibility along with improved crosspol characteristics for the more stringent approvals at upper frequencies.

 

[7mdish]

I wasn't attempting to disappoint, my knowledge of CM reflectors is they have excellent characteristics at both C and Ku band frequencies, though I have also seen ( and purchased ) their 0.8 f/d feeds, which have been offered since 2005/6.

I assume the 1.8 and 2.4 dual reflector versions allow compatibility along with improved crosspol characteristics for the more stringent approvals at upper frequencies.

As I know, my new CM 2.4m is not a dual reflector dish. I let you know if it is, but I don't think so.

 

[7mdish]

And now ladies and gentlemen.... my new dish was delivered!! Oh yes!
I just opened the box and it seems a fantastic 2-pieces fiberglass 2.4m dish.
Hoping to complete the installation in about two or three weeks, I will provide pictures during the job.
The dish is the receive-only 243 version.
So, anyone could explain which differences between 243 and 244? Thanks.

 

[Channel Hopper]

So, anyone could explain which differences between 243 and 244? Thanks.

Only the front end.

https://photos.imageevent.com/qdf_files/technicalgoodies/vendormanualsfolder/antennas/andrewcommscope/Andew%20Type%20244%20KU%20Band%20Anenna_72202.pdf

 

[7mdish]

Only the front end.

https://photos.imageevent.com/qdf_files/technicalgoodies/vendormanualsfolder/antennas/andrewcommscope/Andew%20Type%20244%20KU%20Band%20Anenna_72202.pdf

Sorry but I do not understand. Does it mean RX-only and RX/TX versions? Thanks.

 

[Channel Hopper]

Sorry but I do not understand. Does it mean RX-only and RX/TX versions? Thanks.

Any dish can be used to transmit, but some operate better than others.

 

[7mdish]

Little bit confused.... 244 is better than 243?

 

[Channel Hopper]

Horses for courses. C-band TX might be a stretch.

 

[7mdish]

Probably in the next days we will be able to begin installation.
Anyone could link the PDF official datasheet of this dish please?
I would like to check f/d ratio from the manufacturer. I believe it is 0.6 but I would like to be sure.
The dish is CM 243 receive-only version. Thanks.

 

[RimaNTSS]

@7mdish Look in my post #61, you can find all needed data for feed installation. That can be your starting point. But position of your feed is adjustable, so, you can always find a position of the feed for maximum reception. Remember, the offset angle of the antenna you have is 22,62*, you can use this fixed data to check whether you have placed the feed properly.

 

[7mdish]

Yes RimaNTSS, just downloaded and printed your images two weeks ago.
My installer was really impressed by your pictures. I wanted to introduce him in this board but he does not speak english unfortunately.
I thought that PDF datasheet could be useful. If not, we start from your suggestions.
Hoping to be on fire in some day. Thanks.

 

[ozumo]

Doesn't mention f/d ratio

 

[RimaNTSS]

I would like to check f/d ratio from the manufacturer.

Yes, according to manufactures, F/D of antenna is 0,6. But I do not think you really need this info ATM and at all. You have antenna with opening angle ~80*, then you have your feed with fixed illumination angle (whatever it is). You can not change those parameters, just cope with them. Why do you need F/D? How are you planning to use it?

 

[ozumo]

Probably in the next days we will be able to begin installation.

Hello @7mdish, have you made any progress on the installation?

 

[7mdish]

Hi Ozumo, I did not forget to update this thread, don't worry.
Yes we began the installation but we had a big big, unexpected stop, and this is the reason for which you did not read any update.
To summarize, our plans was to install SSS polarmount requiring a 100mm pole on my existing 90mm pole adding proper bolts to clamp the polarmount.
It was all ready, but unfortunately it did not work. The polarmount was not locked properly, we had unacceptable movements, something that we really did not expect.
I can say that we had not a good idea, it was our big mistake.
Now we must completely replace the pole!
We ordered a new 100mm pole, waiting for delivery form a local manufacturer. When it will be available, we must rebuild the concrete under the roof before installing the new pole, and finally we will be really able to install the dish.
A very very long story, and a very very disappointing moment when we understood that our idea was wrong unfortunately.
Now I suspect that the installation will be completed only after summer holidays, hoping next September.
So, as soon as I have new update I let you know.
Thank you for your interest. Obviously I'm really waiting to have my new dish working on my roof. Thank you again.

 

[ozumo]

It may be possible to sleeve the existing pole with a 100mm diameter pole with 5mm wall thickness.

 

[7mdish]

Hhhmmm.... I don't want any compromise for such installation.
We prefer to make the job from scratch, all new.
My existing pole is an old one, so I decided to replace all parts due to this bad stop, to be able to begin the installation again being sure that all parts are OK this time.

 

[Channel Hopper]

Hi Ozumo, I did not forget to update this thread, don't worry.
Yes we began the installation but we had a big big, unexpected stop, and this is the reason for which you did not read any update.
To summarize, our plans was to install SSS polarmount requiring a 100mm pole on my existing 90mm pole adding proper bolts to clamp the polarmount.
It was all ready, but unfortunately it did not work. The polarmount was not locked properly, we had unacceptable movements, something that we really did not expect.
I can say that we had not a good idea, it was our big mistake.
Now we must completely replace the pole!
We ordered a new 100mm pole, waiting for delivery form a local manufacturer. When it will be available, we must rebuild the concrete under the roof before installing the new pole, and finally we will be really able to install the dish.
A very very long story, and a very very disappointing moment when we understood that our idea was wrong unfortunately.
Now I suspect that the installation will be completed only after summer holidays, hoping next September.
So, as soon as I have new update I let you know.
Thank you for your interest. Obviously I'm really waiting to have my new dish working on my roof. Thank you again.

Ah, yes. Any tolerance between the pole and the polarmount 'sleeve' is going to be an issue. For a 100mm post, a gap of 1mm means the possibility of up to 2% tracking error in all directions (as a comparison the 6.5" post with 1mm gap brings the error down to around 0.45%).

It was alluded to in this thread around post #14

Adapting IRTE Stand for use with 2.4m Dish

Hi all after some advice, I currently have a 2.4m CM languishing in the garage whilst waiting to purchase a polar mount/stand/king post whatnot I have the chance to purchase this stand which was previously used for a 1.8m tin foil dish ie fortec star petal Could this be adapted to take my 2.4m...

www.satellites.co.uk

The later IRTE polarmount has quite a deep sleeve which is clamped around the pole top and bottom, If bolted to the correct tolerance it doesn't move at all, leaving only the actuator rose joints and polar mount bearings as candidates for tracking issues.

I hope the new stand is close to the inside diameter of the polarmount ordered, otherwise you will end up with movement unless welded shut.