Just Sharing This Adapting a Prodelin Polariser.

[John]

Heavy rain at the moment (Sunday) so no outdoor work today but the forecast for the next three days or so is rain free.
Here's a few pics of the lnb to servo motor bracket during construction.
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[John]

Heavy rain at the moment (Sunday) so no outdoor work today but the forecast for the next three days or so is rain free.
Here's a few pics of the lnb to servo motor bracket during construction.
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... Iv'e used a 15Kg/cm torque on my AV-Comm barrel due to using a better needle roller bearing - due to the added weight of the lnb flange assembly and the not so good bearing drag iv'e upgraded to a 35Kg/cm unit to rotate the device.
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[John]

To finalise - Motorised Prodelin polariser project now finished and working very well. Due to better matching of the feed to lnb and also the really well made and finished Prodelin polariser it has gained just over 1 dB across the normal range 3.6 to 4.2 GHz but has gained at least 1.5dB on the 4.5 to 4.8 GHz section of the band which is a real bonus for me with this Elite 2.2 at these extended frequencies.
So, pics of servo bracket made, strip down of the AV-Comm barrel install, Polariser alignment paying great detail to accurate positioning, temp rain cover made from an empty ice cream container ( i did say this was a cheap and cheerful build) & finally the finished article back on the dish. Final final scalar plate tweak to do another day to get the final final sweet spot using the analyser. All exposed and even non directly exposed parts given two coats of plastic sealer spray for added weather protection.
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[moonbase]

Well done John, a great little project a pleasure to read and view the pictures.

 

[John]

Well done John, a great little project a pleasure to read and view the pictures.

Your cheques in the post MB

 

[Captain Jack]

Very nice! I wish I had the time or skill to do all this!

 

[otokoc]

DEAR JOHN
what is your polariser waveguide number? thanks

 

[Channel Hopper]

From the Prodelin charts for prime focus receive only antennas, it mentions part number 0800-3763 however is not clear if this includes the feed as well. 0800 prefixes would normally be an assembly rather than an individual component.
From memory the circular and linear feedhorns are different for the 1252-1374 models and so the manfacturer constructs the complete antenna based on the order, with the feed/polariser assembly complete in one box.

 

[Channel Hopper]

Aha!

PRODELIN C BAND CIRCULAR FEED RECEIVE ONLY FOR 3.7 METER. VSAT | eBay

 

[John]

@ otokoc , iv'e been out all afternoon but yes thats the unit i had off ebay that Channel Hopper has posted. The actual lnb flange is specifically machined to fit the actual polarizer section and is of very high quality and it has a CPR-229 to lnb coupling.
The only other info i have is what it says on the box.
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[otokoc]

ola john
ı am convert my prodelin tx port for rx port.this working but not good

 

[John]

ola john
ı am convert my prodelin tx port for rx port.this working but not good

Ok, keep us informed. We have to experiment just to satisfy our curiosity

 

[Channel Hopper]

The 229 interface has a different frequency response curve to the 137 side, which is tuned for a centre frequency around 6 GHz from memory, the 229 is centred at about 3.8GHz.

 

[John]

.... my search for a Chaparral C-band scalar plate has been fulfilled due to a generous F.O.C donation of a brand new one from Feedsat DXer .
Iv'e further fabricated a new feed front end using a bit of 6mm thick ali plate i had, yet to be fitted. I have a VE4MA (Kumar) type scalar that i will do some experimentation with on the 2.2 Elite PF when the outside working conditions get a little bit more friendly.
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[beavs2112]

ola john
ı am convert my prodelin tx port for rx port.this working but not good

Hello @otokoc. It's a shame you are not getting good results. Is you're signal weak? I think what might help you is what satosk posted in this thread Patriot 3.8m - SatsUK post # 54 he has a picture of what looks like a prodelin dual c-band receive only OMT. maybe message him and ask him where he purchased it and price. I re-copied the picture of what I mean. Sorry to hijack thread temporarily.

 

[John]

... another one of these Prodelin C-band polarisers has been flagged up to me for sale from the USA. They are not cheap but they are exceptionally well made and perform better than the cheaper AV-Comm barrel item. My adaptation of the Prodelin polariser for motorised H/V/L/R use is still performing brilliantly and i would recommend the adaptation if your into home-brew construction.
Link here :- PRODELIN C BAND CIRCULAR FEED RECEIVE ONLY FOR 3.7 METER. VSAT | eBay

 

[John]

Ok - Covid-19 boredom setting in a bit now so needed something to do
My 2.2 Elite C-band rig is a good 3 mtr off the ground to the lnb position so if any micro tweaking has to be done on the feed assembly it either means the whole rig has to be cranked down OR take the dish across to it's extreme East position with motorised elevation taken to the max down position - this then makes the feed reasonably easy to reach off a small ladder.... all in all , a right ball ache. One of my niggles was that i was never too sure or satisfied that i had the scalar in exactly the right position- i was only 99% sure.
So - time to have a rummage in the bits and bobs scrap box that contains years and years of collected bits and bobs to knock up something to make the scalar motorised from the shack under observation from the dish feed cam.
What i knocked up certainly 'aint pretty but it works extreemly well as the scalar ring can be moved in millimetres or less increments and it's performance for optimum scalar position on the feed barrel is monitored on the dish cam and also the Promax FSM - and didn't have to buy anything new really.
The items used out of the junk box are: - a telescope focus rack and pinion with it's control box, a small 12volt angled geared motor and some home brew brackets. There was already a spare 2 core cable running from the shack to the dish position that then got used for the scalar focus motor.
Here's a few picks of the lash up - -

 

[Channel Hopper]

Very nice.

 

[John]

Very nice.

.. ideally i would have liked to have gone with a more smaller less obtrusive rack and pinion fixture but as all of the bits are 'just' & only just, hiding behind the scalar and therefore not adding to any reflector shadowing, plus they were all at hand, i thought nah, it will do.

 

[John]

.. Time for a bit of servicing and a change of lnb on the L/R/H/V C-band rig whilst the weather is decent.
The home brew rotating polariser joint ball bearings needs a check & re-greasing.
There's not a lot of new stuff happening at the moment on the 4.5 - 4.8GHz section so the Norsat 8000RI Extended C- band 3.6 to 4.8GHz lnb is to be taken off and i'll fit a NJS 8486S 3.4GHz to 4.2GHz lnb and check out what's going on since i last looked around the 3.4GHz area for a change.
A touch of adaptation to the flange coupling required due to the NJS having different fixing arrangement which has been done and ready to re-fit on the polariser asap.

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