Just Sharing This Coming to a forum near you soon - mobile dish test rig

John

John

Enthusiast.
Messages
2,304
Location
North Nottinghamshire.
My Satellite Setup
Elite 2.2 PF - CM1.8 - CM1.2 - Gibertini 1.25.
Ku - Ka -C & Ext C.
PC cards-TM5402 receivers.
Promax FSM.
My Location
North Nottinghamshire.
... Interesting results after mounting original CM 1.8 stock arms/feed assembly alongside ref: Jig.

Assuming iv'e not dropped any major clangers (balls ups) with the comparison task it emphasises that for maximum possible performance of a dish / feed, imo, any dish above 1.2 mtr and upwards needs to be double checked and accessed in greater detail than just putting it all together assuming it to be 100% correct. I did the same on my 1.2 Gibby Ka dish set-up.

I'll process some pics asap
 
S

s-band

Specialist Contributor
Messages
821
My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
I agree. I am struggling to get my 1.5 IRTE to exceed the Prodelin Ka 1.2 (on Ku). The Prodelin is on an az-el and has tweakable feed position and skew to get the optimum set-up. The original, fixed position, IRTE feed is about a dB down on an Invacom C120 feed which has variable beamwidth and on which I can move the focal point. (Octagon LNBs, modded to C120, on both)
 
John

John

Enthusiast.
Messages
2,304
Location
North Nottinghamshire.
My Satellite Setup
Elite 2.2 PF - CM1.8 - CM1.2 - Gibertini 1.25.
Ku - Ka -C & Ext C.
PC cards-TM5402 receivers.
Promax FSM.
My Location
North Nottinghamshire.
... Interesting results after mounting original CM 1.8 stock arms/feed assembly alongside ref: Jig.

Assuming iv'e not dropped any major clangers (balls ups) with the comparison task it emphasises that for maximum possible performance of a dish / feed, imo, any dish above 1.2 mtr and upwards needs to be double checked and accessed in greater detail than just putting it all together assuming it to be 100% correct. I did the same on my 1.2 Gibby Ka dish set-up.

I'll process some pics asap



.. Some comparison pics, which helps to illustrate the dodgy illumination mapping on stock set-up.
Next to do is modify the feed position & angles to emulate the ref:
..........................................................................................................................................................................................................................................................................................................
IMG_8621 - reduced..JPGIMG_8628 A - reduced.jpgIMG_8629 - reduced.JPGIMG_8634 - reduced.JPGIMG_8632 - reduced.JPGIMG_86181.8 feed angles.. cropped. reduced..jpg
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
27,833
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK South
So, you suffer from droop.
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
27,833
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK South
I agree. I am struggling to get my 1.5 IRTE to exceed the Prodelin Ka 1.2 (on Ku). The Prodelin is on an az-el and has tweakable feed position and skew to get the optimum set-up. The original, fixed position, IRTE feed is about a dB down on an Invacom C120 feed which has variable beamwidth and on which I can move the focal point. (Octagon LNBs, modded to C120, on both)

Without hijacking the thread, which feed assembly are you using on the IRTE ?

I installed a couple of 1.5 reflectors that were substandard in performance out of the box, they gave a second focus point at approximately 2 degrees off prime, which could be improved but not eliminated by standing off the backplate by different sized grommets.
 
RimaNTSS

RimaNTSS

Super Moderator
Staff member
Messages
4,817
My Satellite Setup
Some SAT-related hardware.
My Location
N-E from Riga
Rima, can you please clarify your ref: dimension B to F on your file - my file pic has that measurement slightly obstructed.
For 1.8m CM it is 1080mm ScreenHunter_970 Sep. 15 17.19.jpg
 
S

s-band

Specialist Contributor
Messages
821
My Satellite Setup
1.5m IRTE PF, Octagon OSLO external Ref., TBS6983,
Various L, S, C, X & Ka bits. 1.2m S/X/Ku/Ka Prodelin on Az-El
My Location
SE UK
Without hijacking the thread, which feed assembly are you using on the IRTE ?

I installed a couple of 1.5 reflectors that were substandard in performance out of the box, they gave a second focus point at approximately 2 degrees off prime, which could be improved but not eliminated by standing off the backplate by different sized grommets.
This one : https://www.satellites.co.uk/forums/attachments/c-ku_1-5m_dsc1003s-jpg.91098/
It came with the earlier feed which has a PTFE dome but was really only for the FSS band, I think.

Interesting. The dish always had an asymmetric pattern. I've got a new back plate for it so I'll keep that in mind when i finally sort it out.
 
Channel Hopper

Channel Hopper

Suffering fools, so you don't have to.
Staff member
Messages
27,833
My Satellite Setup
A little less analogue, and a lot more crap.
My Location
UK South
Hmm

Take the reflector off the backplate, place on a decent flat surface (large plate glass window) and check for edge distortion, refit with grommets, boresight the Ku feed on its own and try again.

Yes, the ice cream cone feed wasn't particularly responsive, though they did make a third type with larger scalar and dielectric plate of hard perspex you could remove.
 
John

John

Enthusiast.
Messages
2,304
Location
North Nottinghamshire.
My Satellite Setup
Elite 2.2 PF - CM1.8 - CM1.2 - Gibertini 1.25.
Ku - Ka -C & Ext C.
PC cards-TM5402 receivers.
Promax FSM.
My Location
North Nottinghamshire.
.. Started the feed re- alignment, didn't really want to butcher the existing feed arms but i can't see me parting with this dish so carried on.
1st job was to put a kick upwards on the bottom lnb arm to cancel out the feed angle error. First attempt pretty close but needs a tad more kick and then shorten the the three arms to bring the focal point to the desired area.
I will also mod the stock CM 1.8 scalar feed so as to allow some forward / backward movement when used with a Ku test lnb.
Any Ka or C-band testing will have a custom feed holder made to suit using the Ref: jig for positional location.
..........................................................................................................................................................................................................................................................................................................
IMG_8636- Bottom arm applied bend - reduced..jpgIMG_8642- Bottom arm applied bend ... reduced..jpgIMG_8650 - - wrong angle - reduced..jpgIMG_8651 - focal point alignment - reduced..jpg
 
RimaNTSS

RimaNTSS

Super Moderator
Staff member
Messages
4,817
My Satellite Setup
Some SAT-related hardware.
My Location
N-E from Riga
@John I have already went through process you are going now. And my final solution is: new, length-adjustable feedarms + universal (C/Ku/Ka) LNB-holder. Holder can hold LNB in any position you wish and pont it to any dot on the surface of the dish. All INOX made. In case you brake original CM feedarms and need replacement I can send a set to you.
 

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John

John

Enthusiast.
Messages
2,304
Location
North Nottinghamshire.
My Satellite Setup
Elite 2.2 PF - CM1.8 - CM1.2 - Gibertini 1.25.
Ku - Ka -C & Ext C.
PC cards-TM5402 receivers.
Promax FSM.
My Location
North Nottinghamshire.
@John I have already went through process you are going now. And my final solution is: new, length-adjustable feedarms + universal (C/Ku/Ka) LNB-holder. Holder can hold LNB in any position you wish and pont it to any dot on the surface of the dish. All INOX made. In case you brake original CM feedarms and need replacement I can send a set to you.


Thanks Rima, i'll keep that in mind :Y
 
RimaNTSS

RimaNTSS

Super Moderator
Staff member
Messages
4,817
My Satellite Setup
Some SAT-related hardware.
My Location
N-E from Riga
But in case when original CM feedarms are used it is better to change plastic LNB-holder. This also can hold C/Ku/Ka LNB and change it's position and direction, but has some limits though.
 

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