Advice Needed SMW Depolariser XD12

[moonbase]

Hi,

I came across a Swedish Microwave depolariser model SM XD12 during a loft search for some other satellite kit. I bought it years ago but cant remember why, another impulse purchase of satellite kit that never gets used! If I recall correctly, I can use it to switch between Linear and Circular polarities by inserting it between a C120 LNB and the C120 feed.

Can anyone please confirm the positions I need to have it aligned with the C120 LNB to switch between linear and circular polarities and if it will introduce appreciable signal loss?

I have attached a few pics below.


Rgds

 

[AndyX]

I used to use one in analogue days but unfortunately it did cause serious signal problems when I switched to digital. A mechanical depolerizer would probably worked better but digital receivers no longer support control. I am not sure that depolerizers are useful now but maybe someone else has more current experience.

 

[Anonymous_1]

This week I have tested it for 56°E but the snr is less good than my old circular LNB.
Here is a thread on ly french board ( I hope link is allow)
http://forum.satelliweb.com/viewtopic.php?f=6&t=10695&start=10

Please find attached picture inside the depolarizer.
But excepted 56° or 36° russian beam, it's better to remove it, the signal decrease about 2 dB I think.

I hope this can help you

 

[Archived-1]

Hi, what way does this item attach to the lnb, option A/B please.

 

[Anonymous_1]

none of them but this one:

View attachment 82409

 

[Archived-1]

Thank you FS, that lnb is no good then for this I guess ?, I will order the one you have , these are ok together please ?

 

[Anonymous_1]

Yes, Invacom is a good LNB for the channel master 1.8m, you can try the Inverto Black pro but not as good as the invacom.

But for Circular , I have best result with the Circular LNB.

PS: according to your picture, is it a 1.80 Channel Master feedhorn, it looks smaller than mine.
It looks like for a 1.20m .

 

[Archived-1]

according to your picture, is it a 1.80 Channel Master feedhorn, it looks smaller than mine.
It looks like for a 1.20m .

Thank you FS, I am unsure tbh you tell me please, it did come with the 1.8 but from a data company that install all sized dishes so it could be of a 1.2 ?, picture with size and model number below.

 

[Anonymous_1]

Here is my measurement for the 1.8m Channel Master Feedhorn




Also I have check the 1.20m Channel master Feedhorn

 

[Archived-1]

Well this is different to both , this is the box it came in I will check skyware to see what they sell for the 1.8 now days to make sure I have the correct one for the 1.8.

 

[Anonymous_1]

Here is my proposal: I have a 2nd Channel Master 1.80m Feedhorn new in box, I can send you this for testing ?

 

[Archived-1]

Maybe skyware changed them ?, this is the leaflet and bits for mine.

 

[archive10]

Hi, what way does this item attach to the lnb, option A/B please.
View attachment 83758 View attachment 83759 View attachment 83760

Don't have an XD12, but I do have an XFR-45 feedhorn (with integrated Fe-rotor). It looks remarkbly like your XD12.
All the SMW feeds are keyed; the holes does not align to the standard C120 eight-holes. (not a square but a rectangle 26.4 x 28.5 mm).
This means that you should only be able to mount the LNB and depolariser in one way.
Is this not so?

 

[archive10]

Well this is different to both , this is the box it came in I will check skyware to see what they sell for the 1.8 now days to make sure I have the correct one for the 1.8.
View attachment 83782 View attachment 83783

@martin-f: the one you have is the official Channel Master/Andrew/ASC/Skyware feedhorn for RxO and class 1 (I believe) LNB assemblies.
It is shared between the 1.0, 1.2, 1.8 and 2.4 metre models using the most common SMC reflectors.
You should be perfectly alright using this - the majority of users has this.

The feedhorn @Feedsat_DXer shows is for an Class II and III Rx/Tx version of the 1.8 and 2.4 metre Andrew dishes.
You can tell that they're made to be used with OMTs and separate LNBs for Rx and Tx on H and V.
I don't think they're made anymore, but I am sure they work well nonetheless.

There are other reflectors that were introduced with Andrew and ASC, those have different ribbing patters, and some I dare guess have different f/D.
The feedhorn Feedsat_DXer shows as a 1.2 metre feedhorn is from one of those "other" Channel Master dishes.
You can tell that they use a different set of feed-arms from the extra bracket that sits on the feedhorn between the clamp and the front.

 

[Archived-1]

This means that you should only be able to mount the LNB and depolariser in one way.
Is this not so?

Hi st1, thank you for the information , it will fit both ways, but having said that I might have been trying to fit it to something I shouldn't

 

[archive10]

Hi st1, thank you for the information , it will fit both ways, but having said that I might have been trying to fit it to something I shouldn't
View attachment 83800 View attachment 83801

Well, they may have changed their minds about keying at some point, but all my SMW stuff is definitely keyed to go one way only.
Attached is a few pics I found from when I took the SMW-OA1050 apart (where most of the bits came from).
I have a similar LNB to your somewhere. Never bothered to try if it works - I am sure the world has moved on in terms of LNB efficiency...

 

[Archived-1]

Never bothered to try if it works - I am sure the world has moved on in terms of LNB efficiency...

Thanks again st1, I have been told the lnb is old hat, but I must try it and see, an old £100 + lnb might work better than a new £6 one is my theory, but the proof is in the pudding .