Just Sharing This Coming soon - - Ex Viasat Ku Motorised Pol/Skew

[RimaNTSS]

@John Nice "red dot counterclockwise movement "!

 

[John]

.. Now mounted on the roof mounted CM 1.2 and working a treat with the motorised Pol / Skew & SMW PLL lnb and re-configured feed position/pointing angle.
Water proofing cover now being fitted.
I'll re-design this idea for a summer project on a spare CM feed to reduce the physical size and weight of the Visiosat lump.
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[Channel Hopper]

Dish illumination / tracking accuracy set-up test - 99.9% accurate, to squeeze the last drop of performance out of the 1.2 dish & obtain this accuracy and still maintain precise new lnb pointing angles / FP etc is a pain and will have to be done again once it gets re-installed on the roof mount CM 1.2mtr - the very very slightest movement of the unit throws the tracking out - 'suppose i could always swap out to a standard 1.5mtr install to achieve the same signal levels and do away with the obsession for maximum efficiency from an installation but there's no fun in that - this way keeps the brain active in these crap troubled times.
I might re do the vid when it gets darker outside but you can see the laser dot reasonably ok in this vid. Laser starts at the bottom of the dish.
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I might have missed it, but did you post a laser test with the feed set as per the manufacturer's position ?

 

[John]

I might have missed it, but did you post a laser test with the feed set as per the manufacturer's position ?

No you didn't miss it - I did a laser vid some time ago on my 1.8 CM test rig with the feed in the manufacturers position when i was building my test rig - it illuminated at the bottom of the dish but as it revolved around to the sides it started to over-illuminate and eventually the top the laser was about 12" above the top of the dish and sucking in noise.
After re-aligning the feed to the adjusted dimensions as per Rima's data it tracked perfectly and a few TP tests showed a better performance.
I did the same on the 1.2 CM test rig at ground level using the manufacturers position and it was the same over-shoot at the sides and top of the antenna but i didn't video it.
The modded feed holder position on the 1.2 CM to Rima's data sheet again corrected the illumination tracking and an increase of at least 1dB or more was observed on selected TP's over a short time period compared to the standard manufacturers position.
It still remains a mystery why this adjusted lnb feed position should show to be better than the factory designed position from Channel Master but iv'e seen it now on two different CM dish sizes to give an increase in performance. Only useful to go to this extreme if your OCD is demanding you to eak the very last drop out of the dish for those border line lock channels or TP's ... normal people probably don't need to go to these extremes

 

[Captain Jack]

Stupid question.... But how do you align the laser assembly? Do you have a picture from the front of it?

 

[Channel Hopper]

No you didn't miss it - I did a laser vid some time ago on my 1.8 CM test rig with the feed in the manufacturers position when i was building my test rig - it illuminated at the bottom of the dish but as it revolved around to the sides it started to over-illuminate and eventually the top the laser was about 12" above the top of the dish and sucking in noise.
After re-aligning the feed to the adjusted dimensions as per Rima's data it tracked perfectly and a few TP tests showed a better performance.
I did the same on the 1.2 CM test rig at ground level using the manufacturers position and it was the same over-shoot at the sides and top of the antenna but i didn't video it.
The modded feed holder position on the 1.2 CM to Rima's data sheet again corrected the illumination tracking and an increase of at least 1dB or more was observed on selected TP's over a short time period compared to the standard manufacturers position.
It still remains a mystery why this adjusted lnb feed position should show to be better than the factory designed position from Channel Master but iv'e seen it now on two different CM dish sizes to give an increase in performance. Only useful to go to this extreme if your OCD is demanding you to eak the very last drop out of the dish for those border line lock channels or TP's ... normal people probably don't need to go to these extremes

Thanks.

The above imagery posted is of the receive only feed system (three arms) which has the feed clamp as a common part amongst all CM reflectors. The uplink design is a single affair that is secured independently of the reflector surface and - like Prodelin - has a small amount of adjustment thanks to the teo bolts at the base of the metal spine. The vertical section of the Channel Master variant has a second set of locking bolts directly under the AZ/EL turret which may also have some tolerance.

https://manualzz.com/doc/43430474/type-183---skyware-global

A wild guess is the team tasked with the receive only models did not lock the mounting points correctly before taking measurements.

Somebody with the later Raven/Skyware models (ideally a Ka band option) might be able to verify if the feed boresight has been updated to the 'correct' position.

 

[Channel Hopper]

The 1.2m Ka model now has three bolts at the mating point.

http://vsatmena.com/main/wp-content...m-Standard-RxTx-Ka-Band-SFL-Antenna_REV-4.pdf

 

[John]

Stupid question.... But how do you align the laser assembly? Do you have a picture from the front of it?

Not at all CJ - this is the way i do it, basically copied off the net or from forum friend 'trust' .
Assuming the feed holder is in the stock CM factory position and not modified ...
Firstly make sure the scalar is at the correct FP position, if the scalar is not motorised then just slacken off very slightly the two fixing screws of the top half of the lnb holder just enough to enable you to manually rotate the whole feed but not too sloppy as to ruin the accuracy of the rotation test.
It's essential that the laser is in perfect alignment along the bore sight of the scalar and the rest of the feed barrel etc behind so as to achieve correct tracking alignment.
Fix the laser with 'BluTack' - it does not have to sit directly onto each of the scalar rings but it must not move when doing the rotation.
Set the laser in the BluTack so the beam just touches the very bottom of the reflector - switch on and rotate carefully, observing or videoing the laser beam tracking all the way around the reflector .
Job done - works for me CJ
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[John]

Not at all CJ - this is the way i do it, basically copied off the net or from forum friend 'trust' .
Assuming the feed holder is in the stock CM factory position and not modified ...
Firstly make sure the scalar is at the correct FP position, if the scalar is not motorised then just slacken off very slightly the two fixing screws of the top half of the lnb holder just enough to enable you to manually rotate the whole feed but not too sloppy as to ruin the accuracy of the rotation test.
It's essential that the laser is in perfect alignment along the bore sight of the scalar and the rest of the feed barrel etc behind so as to achieve correct tracking alignment.
Fix the laser with 'BluTack' - it does not have to sit directly onto each of the scalar rings but it must not move when doing the rotation.
Set the laser in the BluTack so the beam just touches the very bottom of the reflector - switch on and rotate carefully, observing or videoing the laser beam tracking all the way around the reflector .
Job done - works for me CJ
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View attachment 140506View attachment 140507

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Also CJ - the fly in the ointment here is - if your CM feed is fully intact with the front glued on rain cover .
I tend to take mine off so as to aid installation set-up, and then fit a push on cover lastly.
OR -- Blutack the laser on the outside of the intact scalar

 

[Channel Hopper]

The Global Skyware site has detail relating to two variants of the modified 1.2m Raven/CM design

1235817

https://cdn.shopify.com/s/files/1/0501/4949/0883/files/1.2M_Ka_RXTX_Class_III_DRC.pdf?v=13367601691611339891

1235815

https://cdn.shopify.com/s/files/1/0501/4949/0883/files/1.2M_Ka_RXTX_Class_III_XRF.pdf?v=18423383281884436684

I cannot find a similar assembly diagram for the Ka 1.8m model (1815), or the 2.4m model (2415),

 

[Captain Jack]

Thanks John - that's very helpful. Another job to add to my endlessly growing list!

 

[John]

MkII lightweight version being built now
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[Trust]

MkII lightweight version being built now
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View attachment 141246

Very nice build

 

[John]

Just a few more pics of the lightweight version of the motorised Ku feed for the CM roof mounted dish for anybody interested in knocking up home brew stuff ....
Mostly all the bits used are salvaged from the metal scrap bits and bobs or stuff iv'e collected over the years and re-used them.
Waiting for the wire wound 'feed position' indicator pot to arrive and fix onto the main scalar cog.
The 0 - 22Khz switch was an exact fit onto the SMW pll lnb - bonus.
The 12v drive motor ended up on top of the support rail.
** Youtube vid to follow showing initial dish edge tracking.
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The illustration showing illumination pattern shows what i was getting on my CM dishes before and after re-locating the lnb position.
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[John]

Youtube link to initial CM1.2 illumination / tracking set-up to get it in the right ball-park before transferring the feed up onto the identical CM1.2 roof mount for final alignment
** I found it a bit difficult to get the HD option to play out

 

[moonbase]

"Abbie" looks in fine fettle in the background

The 22KHz tone switch looks tailor made for the LNB, very nice fit.

 

[John]

"Abbie" looks in fine fettle in the background

The 22KHz tone switch looks tailor made for the LNB, very nice fit.

Yeah, she likes to be with her Dad and also as a female she's being nosey & watching the world go by as well.
That 22khz switch turned out to be a real bonus - i was fully expecting to mount it way back on the lower lnb arm and then have two separate fly leads coming off onto the back of the lnb.
*Side note - been tracking the full width transponder noise on the upper extended Ku frequency band from Turksat 5B all morning , no actual signal carriers seen yet - it's really calmed down now in movement and is fairly easy to locate it.

 

[moonbase]

*Side note - been tracking the full width transponder noise on the upper extended Ku frequency band from Turksat 5B all morning , no actual signal carriers seen yet - it's really calmed down now in movement and is fairly easy to locate it.

Is that with one of the upper extended Ku-Band LNB's we got as a mini group buy?
I got a box full of them LNB's 'ere, could do with some activity in that band to help boost LNB sales at huge wad.

 

[John]

Is that with one of the upper extended Ku-Band LNB's we got as a mini group buy?
I got a box full of them LNB's 'ere, could do with some activity in that band to help boost LNB sales at huge wad.

Yes it is - it's the one iv'e got on my 1.2 Gibby for looking for & monitoring Upper Extended Ku traffic.