Just Sharing This Adapting a Prodelin Polariser.

[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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This picture might help explain why there are only two fixing bolts to the lnb plus two side clips. All the other lnb threaded fixings were not accessible for one reason or another.

 

[John]

Here's what the lnb 'see's' when bolted to the polariser. Through the Circ pol onto the front waveguide tube to meet it's scalar ring and dish illumination . Elite 2.2mtr PF dish centre shown in the middle.


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[John]

Ok, due to the nasty 5G cell tower interference levels raising their ugly heads now and causing problems with c-band feed frequencies around 3.7GHz it has become necessary to change the method of obtaining H/V/L/R polarity with a frequency range from 3.4 to 4.8GHz C-band.
The old CPR 229 rotating flange type has to go, which has served very well until now, and replaced with a new method to counter attack the 5G virus.
The new rotating system is based on an AV-Comm OMT chosen for it's relatively compact form, imported from Au with extra's added by me during adaptation.
More to follow.....
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[John]

Good time as well whilst stripped down is to do a bit of tidying up of the paintwork / cables etc
Pics ... The old rotating H/V/L/R CPR 229 flange removed, ball bearings taken out and metal faces cleaned ready for mating the AV-Comm OMT
OMT rotational drive cog fitted to OMT
'Lazy Susan' x 2 rotating bearing assemblies fitted and greased up ready to be mated to the Prodelin Circ Polariser face.
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[John]

More or less done knocking this little mod up to fight the 5G virus, just needs the paintwork tidying up a bit and perhaps a final choice of Norsat Cband lnb after more testing.
Bare in mind that these components used in the re-build apart from the new external 5G filter, 4.5-4.8 GHz lnb have been molested many times over the years through experimentation so the install mod you see is not as pretty as it would if all brand new.
Initial tests are good, the single 5G external filter is working good enough to stop the 'swamping' effect caused to the feed / program frequencies at various satellite positions around the 3.7GHz area. The 4.5 to 4.8GHz lnb range didn't need a filter as the 5G cell interference around my location didn't cause any problems... at this stage a cheap 4.5 to 4.8GHz is good enough.
The AV-Comm OMT is advertised as 3.4 to 4.2 GHz operation range but after doing a non-professional but carefully set up bench test using a 4.8GHz signal source into the OMT + lnb's the captured readings on the Promax were identical from both ports which surprised me as i was expecting the side port to show a different reading - off air signals from 65West 4.5-4.8GHz signals showed to be as good if not a bit better than the previous set-up not using the OMT.
A few more nuts and bolts to add onto the 5G filter ends & bit more testing to do but so far worth the effort.
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[scopus]

More or less done knocking this little mod up to fight the 5G virus, just needs the paintwork tidying up a bit and perhaps a final choice of Norsat Cband lnb after more testing.
Bare in mind that these components used in the re-build apart from the new external 5G filter, 4.5-4.8 GHz lnb have been molested many times over the years through experimentation so the install mod you see is not as pretty as it would if all brand new.
Initial tests are good, the single 5G external filter is working good enough to stop the 'swamping' effect caused to the feed / program frequencies at various satellite positions around the 3.7GHz area. The 4.5 to 4.8GHz lnb range didn't need a filter as the 5G cell interference around my location didn't cause any problems... at this stage a cheap 4.5 to 4.8GHz is good enough.
The AV-Comm OMT is advertised as 3.4 to 4.2 GHz operation range but after doing a non-professional but carefully set up bench test using a 4.8GHz signal source into the OMT + lnb's the captured readings on the Promax were identical from both ports which surprised me as i was expecting the side port to show a different reading - off air signals from 65West 4.5-4.8GHz signals showed to be as good if not a bit better than the previous set-up not using the OMT.
A few more nuts and bolts to add onto the 5G filter ends & bit more testing to do but so far worth the effort.
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That's one big lump hanging off the dish luv...

 

[Channel Hopper]

That's one big lump hanging off the dish luv...

John is certainly well hung.......

 

[John]

John is certainly well hung.......

Oh you are awful - can't trust you to keep 'owt to yourself these days

 

[moonbase]

@John

Could you please tell me how the cog is secured/mounted on to the OMT?

 

[John]

@John

Could you please tell me how the cog is secured/mounted on to the OMT?

ebay item - The item was nearly 1mm undersized on the I/D to fit over the OMT front barrel so it had to be machined out to make a really really tight push fit.
See the four holes on the cog - after machining out there was just enough of the holes left showing, the pic shows the 'flat' side of the cog but on the other side it has a 'U' shaped trough going all the way round - a piece of tape was put over the holes on the flat side, turned the OMT up vertical to reveal the 'U' trough, centred the cog wheel up to make it a true circulating wheel without any discrepancies and then poured epoxy resin all the way around and into the holes - once cured the next day the cog was rock solid. Due to the OMT using two 120mm 'Lazy Susan' bearing assemblies sandwiched together, the unit revolves with ease with no real pressure exerted on the cog fixing.
The two 'Lazy Susans' were used because: 1, I had them. 2, They were more or less the right size.
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[moonbase]

ebay item - The item was nearly 1mm undersized on the I/D to fit over the OMT front barrel so it had to be machined out to make a really really tight push fit.
See the four holes on the cog - after machining out there was just enough of the holes left showing, the pic shows the 'flat' side of the cog but on the other side it has a 'U' shaped trough going all the way round - a piece of tape was put over the holes on the flat side, turned the OMT up vertical to reveal the 'U' trough, centred the cog wheel up to make it a true circulating wheel without any discrepancies and then poured epoxy resin all the way around and into the holes - once cured the next day the cog was rock solid. Due to the OMT using two 120mm 'Lazy Susan' bearing assemblies sandwiched together, the unit revolves with ease with no real pressure exerted on the cog fixing.
The two 'Lazy Susans' were used because: 1, I had them. 2, They were more or less the right size.
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@John

Many thanks for the reply, nice work with the cog, it sounds like it is a nice tight fit.
Have you invested in a lathe re machining out the cog, they seem to be very useful once you get into a bit of serious modding?

What sort of signal level increase are you getting with the anti 5G setup compared to without it?
Any EBSpro screen shots of before/after for signal level comparisons?

 

[Channel Hopper]

Oh you are awful - can't trust you to keep 'owt to yourself these days

Well it was almost three years to the day since I last handled it.

 

[John]

Well it was almost three years to the day since I last handled it.

There you go again !.

 

[John]

@John

Many thanks for the reply, nice work with the cog, it sounds like it is a nice tight fit.
Have you invested in a lathe re machining out the cog, they seem to be very useful once you get into a bit of serious modding?

What sort of signal level increase are you getting with the anti 5G setup compared to without it?
Any EBSpro screen shots of before/after for signal level comparisons?

We all know the importance of a nice tight fit, as you very well know luv
No lathe here yet MB, i'm very much a hand's on with hand tools etc - Big vice / Ped drill / Bench grinder / Battery drills / Evolution Universal blade Chop saw / BIG HAMMER - Iv'e no real engineering workshop so to speak i just have to struggle through with what iv'e got . Have to admit though i have been keeping an eye out for a small lathe that doesn't cost the earth but for the amount of time i actually need one kind of puts me off a bit and brings me back to earth
Re: Before/after - - I made & posted video's from the Promax earlier on which prompted me to do something about the 5G interference problem showing the amount of damage it was causing to the reception - iv'e just made notes on my latest medlings. There is defo a slight but useful increase (for me anyway) .
Ive seen a bit of an increase in 4.2-4.8 activity over the year so that was one of the reasons i wanted to keep the 4.5-4.8GHz reception option.
*If there was no 5G interference problem i could have carried on using my Norsat 8000RI full range lnb on the old system, the snag is though my 5G External filter , which i now have to use, has a pass band from 3.7-4.2 GHz and cut's off stone dead the frequencies at 4.5-4.8GHz making the Norsat 8000RI unusable.

 

[Channel Hopper]

John could start a business with his experience of cog rings.

Btw. there are cutoff filters available for ranges 3.8 - 4.0 and 3.9 to 4.1 GHz but they are not cheap.

 

[John]

John could start a business with his experience of cog rings.

Btw. there are cutoff filters available for ranges 3.8 - 4.0 and 3.9 to 4.1 GHz but they are not cheap.

I think i saw an External 5G filter on my searches that covered / passed 3.7 up to 4.8GHz which would have been suited but i needed to re-mortgage the house to pay for it so went for the cheap skate and more fun way

 

[John]

I was having some issue's off 40.5W with a LHC Tp that was a bit of a puzzle - i had it in my mind that it might be a matching problem of the Prodelin ribbed polariser into the AV-Comm OMT build iv'e just had a dabble with so i knocked up another transition from the Prodelin polariser using a Cband 'Single feed' waveguide. Long story short - The actual problem turned out to be my Norsat PLL lnb but the new transition seems to be a better match.
A few pics of the knock up ....
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[moonbase]

I was having some issue's off 40.5W with a LHC Tp that was a bit of a puzzle - i had it in my mind that it might be a matching problem of the Prodelin ribbed polariser into the AV-Comm OMT build iv'e just had a dabble with so i knocked up another transition from the Prodelin polariser using a Cband 'Single feed' waveguide. Long story short - The actual problem turned out to be my Norsat PLL lnb but the new transition seems to be a better match.
A few pics of the knock up ....
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Is the C-Band single feed in the pics one of the cheap Chinese Ali Express jobs, looks like a few of the bolt holes have been drilled out for LNB alignment?
I have both the single and dual feed versions here that I was thinking of trying out with an external 5G filter. The Chinese feed(s) are quite light and do not add much weight to the entire feed assembly.

 

[John]

Is the C-Band single feed in the pics one of the cheap Chinese Ali Express jobs, looks like a few of the bolt holes have been drilled out for LNB alignment?
I have both the single and dual feed versions here that I was thinking of trying out with an external 5G filter. The Chinese feed(s) are quite light and do not add much weight to the entire feed assembly.

Yep, one of the cheapies from China and the holes were drilled out at some time in the past to make whatever fit at the time

 

[Manikm909]

Yep, one of the cheapies from China and the holes were drilled out at some time in the past to make whatever fit at the time

you're up early @John