Just Sharing This 2.2mtr Elite / Precision resurection... Part 2.

[blademedia]

Thank you for the explanation. I have another question if you can please help? Is it the distribution/depth of the scalar rings on the scalar or the forward/backward location of the scalar on the feed that matches it to the F/D?

Both, the scalar depth and size will match a certain F/D range,

Moving the scalar forward reduces the area of the dish that the feed can see, moving it backwards ( away from the dish) increases the area of the dish that the feed can see.

I notice that Chapparal and other vendors place a scale on the side of the feed to indicate adjustment points for different F/D with the same scalar. Presumably this works to some degree but is not the perfect solution?

This is a general guide as you say D not a perfect solution, without the proper equipment that will cost thousands of pounds its trial and error and can take weeks to get correct.

 

[blademedia]

I'm back at 53° East for a short while BM, any freq in particular you had in mind

Put the kettle on J, I'm just on my way up to Nottingham

 

[John]

Put the kettle on J, I'm just on my way up to Nottingham

;) ... not going anywhere, just took the car to the garage for it's M.O.T and then wait for the dreaded call around 4pm to say it's passed or failed. It's as bad as going to the dentist !.
But ... it has it's good side - because i'm housebound means i can have another tweek on the feed a bit later when the sun comes out lol.

 

[blademedia]

;) ... not going anywhere, just took the car to the garage for it's M.O.T and then wait for the dreaded call around 4pm to say it's passed or failed. It's as bad as going to the dentist !.
But ... it has it's good side - because i'm housebound means i can have another tweek on the feed a bit later when the sun comes out lol.

Hope the car passes its test J, it was only a flying visit, I have a property at Blyth Nottingham, unsure how far away you are from me, I will have to pop in and have a look at your dish when I'm up for a few days in the summer.

 

[John]

Hope the car passes its test J, it was only a flying visit, I have a property at Blyth Nottingham, unsure how far away you are from me, I will have to pop in and have a look at your dish when I'm up for a few days in the summer.

Car passed ok thankfully lol, pop in any time your passing, no problem.

 

[blademedia]

Car passed ok thankfully lol, pop in any time your passing, no problem.

That's good news then J, I will call in one day when we are up will let you know and see if its convenient, I like looking at nice dishes.

 

[moonbase]

... It's as bad as going to the dentist !...

If you have most of your own teeth and hair at retirement age you are doing OK. A trip to the dentist could be looked upon as a sign of well being

Rgds

 

[John]

I was asked earlier on in the thread what it would perform like on Ka or Ku, can't place either at true focus as this is a dedicated C-Band only reflector but can get pretty close to focus as a compromise.
Going to try this for a bit of an experiment & evaluation on the 2.2 ...... nothing to loose, easy as just changing scalar ring that has only one fixing screw. If it degrades C-Band performance too much then off it comes -- i have Ka & Ku bands covered already using other dedicated dishes.

Iv'e got a spare flat scalar, the same as what's in use now on the 2.2 for C-Band only.
Iv'e grafted the Inverto Ka/Ku onto it as close to focus as i can get.
Iv'e got reference readings and physical locations of equipment of dedicated C-Band frequencies documented prior to fitting the modded scalar to enable comparison.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

[Channel Hopper]

I was asked earlier on in the thread what it would perform like on Ka or Ku, can't place either at true focus as this is a dedicated C-Band only reflector but can get pretty close to focus as a compromise.
Going to try this for a bit of an experiment & evaluation on the 2.2 ...... nothing to loose, easy as just changing scalar ring that has only one fixing screw. If it degrades C-Band performance too much then off it comes -- i have Ka & Ku bands covered already using other dedicated dishes.

Iv'e got a spare flat scalar, the same as what's in use now on the 2.2 for C-Band only.
Iv'e grafted the Inverto Ka/Ku onto it as close to focus as i can get.
-------------------------------------------------------------------------------------------------------------------------------------

If the feed is off the central focal point by more than a few millimetres then you will end up with different phase wavefronts cancelling out the overall signal.

The Ka tolerance for commercial reflector surfaces is in the region of half a mm, any more and it's downgraded to Ku use.

 

[John]

I was asked earlier on in the thread what it would perform like on Ka or Ku, can't place either at true focus as this is a dedicated C-Band only reflector but can get pretty close to focus as a compromise.
Going to try this for a bit of an experiment & evaluation on the 2.2 ...... nothing to loose, easy as just changing scalar ring that has only one fixing screw. If it degrades C-Band performance too much then off it comes -- i have Ka & Ku bands covered already using other dedicated dishes.

Iv'e got a spare flat scalar, the same as what's in use now on the 2.2 for C-Band only.
Iv'e grafted the Inverto Ka/Ku onto it as close to focus as i can get.
Iv'e got reference readings and physical locations of equipment of dedicated C-Band frequencies documented prior to fitting the modded scalar to enable comparison.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Well ...... it works in a fashion, but there are too many negatives to make it worth while. As to be expected really with a largish reflector not designed for Ka use, a strap-on in this case is not a viable option. A strap-on in other fields is another story. It worked no better if at all than my 1.2 Gibby with the same lnbf but at focus and finely tuned.
It just confirms what i already knew really that for optimum performance on any band the lnb / lnbf must be at focus and tuned / aligned properly.
I just don't have the will at the moment to remove the C-Band feed install to take it to the next level by putting the Ka/Ku Inverto at focus as i feel sure the end result will be probably just a tad better than the 1.8 CM that had one at focus.
@MB .... something you could try perhaps on your 2.2 re-furb ??.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

[John]

Well ...... it works in a fashion, but there are too many negatives to make it worth while. As to be expected really with a largish reflector not designed for Ka use, a strap-on in this case is not a viable option. A strap-on in other fields is another story. It worked no better if at all than my 1.2 Gibby with the same lnbf but at focus and finely tuned.
It just confirms what i already knew really that for optimum performance on any band the lnb / lnbf must be at focus and tuned / aligned properly.
I just don't have the will at the moment to remove the C-Band feed install to take it to the next level by putting the Ka/Ku Inverto at focus as i feel sure the end result will be probably just a tad better than the 1.8 CM that had one at focus.
@MB .... something you could try perhaps on your 2.2 re-furb ??.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

What i do recommend though, as seen in the pic, is the use of a strawberry trifle pot as a throat cover. Can be bought as a pack of three from your local co-op and very tasty indeed.

 

[moonbase]

...@MB .... something you could try perhaps on your 2.2 re-furb ??.

John,

The 2.2m refurb dish needs pulling back into shape, there was a 2mm gap on a string test so I would not hold much hope out for its use as a Ka dish. However, when I get the project started and to the point where the dish is ready to cobble up a quick test I can give it a try.

Rgds

 

[John]

Well ...... it works in a fashion, but there are too many negatives to make it worth while. As to be expected really with a largish reflector not designed for Ka use, a strap-on in this case is not a viable option. A strap-on in other fields is another story. It worked no better if at all than my 1.2 Gibby with the same lnbf but at focus and finely tuned.
It just confirms what i already knew really that for optimum performance on any band the lnb / lnbf must be at focus and tuned / aligned properly.
I just don't have the will at the moment to remove the C-Band feed install to take it to the next level by putting the Ka/Ku Inverto at focus as i feel sure the end result will be probably just a tad better than the 1.8 CM that had one at focus.
@MB .... something you could try perhaps on your 2.2 re-furb ??.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

And .... 321 were back in the room
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
View attachment 105336 View attachment 105336

 

[John]

@MB , for when you start on your 2.2 Precision/Elite. These starter measurements taken off mine after many many tweaks might help you to at least start in the ball park for when you start to get into the tune-up stage. Of great importance is to get equal distances from scalar edge to reflector edge from 3 or 4 positions and perfect bore sight of waveguide to centre hole of reflector. You might have to tweak a mm or so from these measurements on your particular lump but it will put you pretty close..... so get your finger out ;)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

[moonbase]

...These starter measurements taken off mine after many many tweaks might help you to at least start in the ball park for when you start to get into the tune-up stage...

John,

Many thanks for the measurements/pictures.

The holesaw with arbor were delivered yesterday to cut the wooden plug to hold the laser in the feed barrel and the short length laser is out for delivery today. I think I have all the other tools so its just a matter of getting the time to start the project.

Going back to the measurements and the focal point depth inside the feed barrel, it's possible to get a close approximation of this depth for any dish/feed/band using an online triangle calculator, provided you know the feed beamwidth angle and the internal diameter of the feed. The feed beamwidth angle is available via an online calculator that was linked to previously by someone.

I have attached a couple of pictures that present the calculation for your Elite 2.2m dish, I took the feed beamwidth angle from the value you posted previously.


Triangle Calculator
Right-Angled Triangle Calculator

Feed Beamwidth Angle
Prime Focus Satellite Antenna reflector calculation


Using the pictures I have attached as a guide:
1. For "edge a", use half the internal feed diameter (31.3mm for AV-COMM barrel)
2. For "angle A", use half the feed beamwidth angle of the dish (72.75 degrees for an Elite 2.2m)
3. Click the "Calculate It" button
4. The depth of the focal point inside the feed is listed in the "edge b" box

It's only a theoretical result and will not be as accurate as manually tuning the feed. However, it might help get the user into the ball park as a starting point for finer manual tuning. For the Elite 2.2m dish, it calculates the focal point depth at 9.72mm which is a little out from your manually fine tuned value which is to be expected. The manual fine tuning is a real world value that is precise, the calculated value is only theoretical.


Rgds

 

[John]

John,

Many thanks for the measurements/pictures.

The holesaw with arbor were delivered yesterday to cut the wooden plug to hold the laser in the feed barrel and the short length laser is out for delivery today. I think I have all the other tools so its just a matter of getting the time to start the project.

Going back to the measurements and the focal point depth inside the feed barrel, it's possible to get a close approximation of this depth for any dish/feed/band using an online triangle calculator, provided you know the feed beamwidth angle and the internal diameter of the feed. The feed beamwidth angle is available via an online calculator that was linked to previously by someone.

I have attached a couple of pictures that present the calculation for your Elite 2.2m dish, I took the feed beamwidth angle from the value you posted previously.


Triangle Calculator
Right-Angled Triangle Calculator

Feed Beamwidth Angle
Prime Focus Satellite Antenna reflector calculation


Using the pictures I have attached as a guide:
1. For "edge a", use half the internal feed diameter (31.3mm for AV-COMM barrel)
2. For "angle A", use half the feed beamwidth angle of the dish (72.75 degrees for a Precision 1.5m)
3. Click the "Calculate It" button
4. The depth of the focal point inside the feed is listed in the "edge b" box

It's only a theoretical result and will not be as accurate as manually tuning the feed. However, it might help get the user into the ball park as a starting point for finer manual tuning. For the Elite 2.2m dish, it calculates the focal point depth at 9.72mm which is a little out from your manually fine tuned value which is to be expected. The manual fine tuning is a real world value that is precise, the calculated value is only theoretical.


Rgds

Nice info there D, iv'e used the beamwidth calculator on mine which gave a position for the focal point to land 10mm inside the feed, so not a million mile away. Up to now i'm running at about 5.5mm inside the throat with the scalar distance as shown on the pic.
I'll have a play with the Triangle Calculator and see what it gives me.

 

[moonbase]

Nice info there D, iv'e used the beamwidth calculator on mine which gave a position for the focal point to land 10mm inside the feed, so not a million mile away. Up to now i'm running at about 5.5mm inside the throat with the scalar distance as shown on the pic.
I'll have a play with the Triangle Calculator and see what it gives me.

@John

As I said in the original post, it only gives an approximate figure. It is no substitute for the time and effort that you put in to get the measurements absolutely spot on.

Rgds

 

[blademedia]

Mine works out at 15mm for C 3mm for KU, ive not fine tuned C band will see where it ends up when I install it, Ku band works best a nats over 5mm, so it does give us a good starting point to tweak from.

 

[Captain Jack]

Hi John, probably not ideal on a PF but have you thought about an LNB changer of some sort there - perhaps something akin to an old Irte LNB mover from the 90s where it moves along a horizontal bar.

Would get you back into Ku and Ka world again.

 

[John]

Hi John, probably not ideal on a PF but have you thought about an LNB changer of some sort there - perhaps something akin to an old Irte LNB mover from the 90s where it moves along a horizontal bar.

Would get you back into Ku and Ka world again.

Yep, thought about it Alex but it's not really an easy or practical task. The 1.8 offsets are ideal with lnb changers that have various bands covered from C to Ku to Ka or higher but they are only just acceptable for decent C-band performance and leave you wanting bigger, but ... that then gives you a limited choice of a 2.4 offset which is a right lump to house & kit out with gear. Also they would be so critical to positioning on Ka that it would probably be a nightmare to operate on a domestic set-up ,with such a tight beam, and any slight breeze to move the reflector, would loose lock. A mini farm imo , with dedicated tuned reflectors for the desired band is the way to go i think if you can get away with it. I have a mini farm, a 1.2CM for Ku only and a 1.25 Gibby with a changer for different Ka bands which works well but only covers a limited part of the arc due to surrounding brick work ... something like 50°East to 15°West. I'm thinking about a summer project of replacing the 1.25Gibby with a 1.5Gibby + changer, modify the present wall mount so that it will see a lot more arc..... we'll see - might do,might not.