Just Sharing This New bracket for 1224

[gap30]

Excellent job well done

 

[Pipedream]

I have just gone to fit the feed arms and LNB and came across this, anybody got any idea what type of fittings they are.

 

[RimaNTSS]

On first two pictures it is electromagnetic polarizer - old stuff. I have the same somewhere.

 

[Pipedream]

On first two pictures it is electromagnetic polarizer - old stuff. I have the same somewhere.

What do they do, the polarizer was bolted on the back of the center boss with the LNB bolted on the polarizer. The problem I have is a C120 lnb won't fit onto the bolt holes.

 

[RimaNTSS]

It is to change polarization - without voltage polarization is, for example V and when voltage is on then polarization changes to H.

 

[Channel Hopper]

It's going to wreck the LNB feed and your viewing choices unless you fit a water cooled additive.

 

[purplemarina]

leave the polarizer off, the lnb should fit on to the 4 bolt holes using all or some of the holes, you adjust the skew by releasing the allan bolts and twisting.

 

[moonbase]

The black fitting that you have is the Precision Ku band feed with a Precision C120 transition attached to it by three allen bolts and washers. If you separate the C120 transition from the Ku feed, the polariser should fit between them.

Nearest to the dish will be the Ku feed with the three threaded studs, next in line will be the polariser, next in line will be the C120 transition and finally a C120 LNB.

However, you need a receiver such as an old Echostar LT8700 or similar to power the polarizer. Nowadays its probably best to leave it out of the chain and just use the two Precision parts with an LNB.

 

[John]

Top class job, well done, it looks really good.

... Seconded

 

[jeallen01]

It's going to wreck the LNB feed and your viewing choices unless you fit a water cooled additive.

Water and LNB electronics "don't like each other"

 

[Channel Hopper]

Water and LNB electronics "don't like each other"

Racal has been doing it for years.

Really messed up with this design for consumers, but hey! They sold a few thousand duds along ppt the way.

Communication Services via Satellite

 

[jeallen01]

Racal has been doing it for years.

Really messed up with this design for consumers, but hey! They sold a few thousand duds along ppt the way.

Communication Services via Satellite

Lot of pages there - which one(s)?

 

[Pipedream]

I will have another look tomorrow, when I tried to fit the C120 lnb without the polarizer the holes did not appear to line up.

 

[Channel Hopper]

I wouldn't bother, ferrite stuff was all frequency dependent, and the 'ferrite' was simply shoved in the 'jacksey'

All low Ku as well, a proper pigs ear.

This bunch wanted to send people into space....l

 

[jeallen01]

Ferrite LNB polarisers were very useful, especially before modern high power sat transponders and low noise LNBs, because you had a lot more control over the actual skew angles used - you could adjust the polarisation "little by little" to home in on the best angle for receiving a particular transponder, and then store that on a transponder-by transponder basis in the Rx. Used that a lot on the NEC 5000 Rx "in the day"

Early voltage-controlled polariser LNBs were, by comparison, very crude, and at the time I regretted the compromise that just gave you the "H" or "V" options as you couldn't then optimise received signals without physically turning the LNB (even though it substantially reduced the Rx & LNB circuitry, and needed fewer cables between the two).

 

[Channel Hopper]

Ferrite LNB polarisers were very useful, especially before modern high power sat transponders and low noise LNBs, because you had a lot more control over the actual skew angles used - you could adjust the polarisation "little by little" to home in on the best angle for receiving a particular transponder, and then store that on a transponder-by transponder basis in the Rx. Used that a lot on the NEC 5000 Rx "in the day"

Early voltage-controlled polariser LNBs were, by comparison, very crude, and at the time I regretted the compromise that just gave you the "H" or "V" options as you couldn't then optimise received signals without physically turning the LNB (even though it substantially reduced the Rx & LNB circuitry, and needed fewer cables between the two).

The mechanical polariser or polarotor was the design the ferrite tried to mimic. Almost all receivers had pulse circuitry to drive the small motor, but with the advent of this (and IRTE had an almost equivalent useless two wire version) the manufacturers had to provide two more connectors on the rear panel, as well as a few more lines of code for the on screen display. Some never realised the skew was frequency dependent, giving the user just two positions per satellite when individual settings per channel was required, though memory limitations might have had something to do with it.

I think changes in outdoor temperature also affected the resultant skew, though it may have been the resistance of the coil, or the connector characteristics affected by damp and /or humidity.

They also had odd notch issues up the DBS section of Ku band , and lossy at the upper Telecom bands,

4052 or perhaps 4502 was the Racal model number, horrible.

 

[moonbase]

I will have another look tomorrow, when I tried to fit the C120 lnb without the polarizer the holes did not appear to line up.

@Pipedream

I can see the issue that is causing the confusion. You have a Precision C120 transition with a rectangular waveguide aperture on the output end. The aperture size is 0.7" x 0.5" which is somewhere between WR62 and WR75 sizes. I have uploaded a couple of pictures below that show both the version you have and the version with the round aperture at the output end.

The C120 transition that you have was intended to be used with LNB's that have a rectangular input waveguide. I have uploaded a couple of pictures of a Cal Amp LNB that has this type of waveguide. This type of Ku Band LNB is still available and there are quite a few on eBay at sensible prices.

Lastly, if you look into the throat of an Invacom C120 LNB you can see that it is not circular. The connecting C120 flange has a circular input but after that the aperture is almost square. You should be able to connect your C120 transition to an Invacom C120 LNB so that you have quite close alignment of the apertures. After that, its a case of get it on the dish and have a scan to see how it performs.

 

[Pipedream]

I have managed to get 2 bolts to line up so the lnb is on. The lnb moonbase is showing above with the square end, the dish came with 2 of these I will have to try them to see if they are any good. Time now to see if I can get any decent reception with this dish.