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SMW LNB and OMT

Likvid

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#1
I have a 90cm gregorian dish and was thinking of buying SMWs WDL Digital LNB and OMT to install on my dish, i can't have bigger dish as i only have a small balcony.

Currently i have been thinking of buying the MTI AP8-TW LNB.

I am going to use the dish primarily for the weak Astra 2D and i want really the best quality components in my system.

I used to have SMW products 10 years ago when i worked with SAT systems but things change over time.

Is it still the BEST you can buy for money today?

Would i get the same or even a little better result with 2 SMW WDL Digital LNBs and SMW OMT than the MTI LNB?

The SMW seems also on specs to have better phase noise than MTI.
 

Old Satellite

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#2
The problem is that the normal Sky box is expecting to see a normal universal lnb and control the polarity of the vertical and horizontal signals itself.- and change frequency bands.

With an orthmode you normally would have one vertical and one horizontal LNB and the receiver would select the correct lnb -actually a receiver with a 0/12 volt switch for example and then in the menu you would select the correct vertical or horizontal LNB.

Additionally then you will also have a problem due to the normal othermode lnb itself which is normally then for a single band 10.95 - 11.7 for example.

THE ADVANTAGE OF THE ORTHMODE is however as you know is that as there is no poloriser there are no losses due to it either.

It is possible - but is it worth it ? normally the poloriser loss is not normally such an high cause factor. max advantage gain from its removal is typically from 0.1 to 1 db dependent on your current LNB and feed setup.

regards

Old Satellite
 

Likvid

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#3
Yes i know i need switches and all that, the SMW WDL Digital LNB got two outputs, one for low-band and one output for high-band.

The SMW OMT can handle 10.7-12.75GHz according to their specs and it got insertion loss of max 0.1dB

The nice thing with using the OMT is that you get perfect image rejection compared.

I need every 0.1dB i can get so i can't afford a polarizer which have losses up to 0.4dB, then there would be no use to have the excellent high gain gregorian dish.

The phase noise seems much better on SMW than all the rest out there.

I am waiting for a quote for this kit now, i have to see what i will do.
 

Channel Hopper

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#4
the wdl lnb has a wr75 flange and so will only receive one polarity either horizontal or vertical, and so you would require two of them , which gets expensive and introduces the chance the lnbs will be in the way of the signal on a gregorian dish

at least with the MTI it will only be a single transition between feed and lnb, however the lnb will have to be installed at 90 degrees to its usual position to clear the line of signal, and so the polarities out of it will have to be reversed at the switch

I have had very good results with the AP series but as you say, phase noise and matching to the feed are very important. I think the loss through the switch after the lnb is likely to be the main problem.
 

Likvid

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#5
That is my biggest worry that the second LNB will partially block the subreflector.

Maybe the SMW X-Line LNB is a better solution coupled to a SMW XF45 ferrotor?

The X-line got the same specs as the WDL version.

Could you explain to me why people doesn't use polarizers or ferotors anymore?

When i worked with these things 10 years back we always used polarizer/ferotors on motorised systems to get the last signal out of the dish.


Channel Hopper said:
the wdl lnb has a wr75 flange and so will only receive one polarity either horizontal or vertical, and so you would require two of them , which gets expensive and introduces the chance the lnbs will be in the way of the signal on a gregorian dish

at least with the MTI it will only be a single transition between feed and lnb, however the lnb will have to be installed at 90 degrees to its usual position to clear the line of signal, and so the polarities out of it will have to be reversed at the switch

I have had very good results with the AP series but as you say, phase noise and matching to the feed are very important. I think the loss through the switch after the lnb is likely to be the main problem.
 

Old Satellite

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#6
Well in actuality both Polorotors and magnetic polarisers are still in use but primarly in the commerical World, prime reason for lack of use to day is cost versus what a customer is willing to pay.

If you think of the the cost of a normal sky system and then you start to add more cost for an additional poloriser then most customers simply would object even if the performance was better.

One of the best options today is still a Polorotor if you wish minimal loss while acheiving high skew adjustment.However not for a sky set up - could be done but not so simple.

The xf 45 ferrorotor is very good normally with a minimal insertion loss ( i still have one in use. And will help to ensure that the skew is optimally aligned, compared with a normal universal lnb.

In addition there is a very large oppotunity that you will obstuct the dish

I agree with channel hopper the switch may indeed in itself create the same loss.

- sure that you can not squeze a 1.2 mtr ?Which reciever do you have? may be an option ?

Regards

Old Satellite
 

Channel Hopper

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#7
I opt for a mechanical polariser (vane type) over the magnetic version as it is independent on frequency (useful for network scanning)

Having a mechanical polariser allows you to gain those small improvements in signal quality on obscure tansmissions near the horizon on a steerable dish.

Cost of the universal lnb (and the single cable solution) for many broadcasters looking for joe public to sign up, has overshadowed the advantages. How many thread do you see where viewers cannot see certain channels as a result of the spanner monkey not realising that there is 15 or so degrees of skew in the LNB holder.
 

Likvid

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#8
Old Satellite said:
One of the best options today is still a Polorotor if you wish minimal loss while acheiving high skew adjustment.However not for a sky set up - could be done but not so simple.
Are you talking about the difficulty fitting a XF-45 to a Sky minidish?

Hehehe..pretty funny as the SMW XF-45 cost nearly as much as the Sky Minidish and Sky LNB together.

Old Satellite said:
The xf 45 ferrorotor is very good normally with a minimal insertion loss ( i still have one in use. And will help to ensure that the skew is optimally aligned, compared with a normal universal lnb.
After checking the cross polarization number for the XF-45 it says 20dB, the SMW OMT says 31.5dB and the MT AP8-TW says 25dB.

So clearly the OMT seems like the best one in this case but it will be hard to fit it on that dish without obstructing the signal.

Old Satellite said:
- sure that you can not squeze a 1.2 mtr ?Which reciever do you have? may be an option ?
Not possible, the balcony is so tight that it barely fits the 90cm :-)

I am very lucky to live in an area that is inside the sidelobe of the Astra 2D beam so it is possible to receive it on dishes 80cm and above.
 

Old Satellite

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#9
No in short an orthomode is near zero loss 0.1 db and the loss is normally at the higher frequencies due to design of the wave guide.

The Polorotor is next on my list and ideally a seavey feed would be nicer still, however my own ADL CP 400 have perfomed very well.Measured signal in KU band is 1.5 db minimum better than the normal Chapperal corotor.

Magnetic polarisers are a comprimise - normally you will lose between 0.1 and 0.4 db the xf 45 is still cheap to compare with a polorotor option. I was refering to the situation when the dish is motorised and not limited to a single fixed satellite. as for the claims on cross plorisation - that remains what they are.

Bigger dish - can youbend the rails a little so that it fits or lift the dish above them ?


Regards

Old Satellite
 

Likvid

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#10
Do you think it's better for me to order a polarizer without feed from Seavey compared to the other solutions we discussed?

I checked Seaveys site and they have polarizer called PR-120, but it only specifies the range 11.7GHz to 12.2GHz, do you think it really matters?

And then i buy a SMW WDL Digital LNB or the X-line version.

Do you think that is the smartest solution for my motorized 90cm gregorian dish?

I have the Echostar LT-8700 receiver from my old setup but i am going to order the new upcoming Echostar DVR-7210.

The Seavey flange hole is 19mm as on the Fibo feed i have so it is a perfect match.

What is really the difference between the SMW WDL Digital LNB and the SMW X-Line on their site?

I have noticed that you change between low and high band on the X-Line wtih 13/18v and the SMW WDL instead got separate outputs for high and low band.

But what else differ? is it just a matter of taste? they do perform similar?


Old Satellite said:
The Polorotor is next on my list and ideally a seavey feed would be nicer still, however my own ADL CP 400 have perfomed very well.Measured signal in KU band is 1.5 db minimum better than the normal Chapperal corotor.

Magnetic polarisers are a comprimise - normally you will lose between 0.1 and 0.4 db the xf 45 is still cheap to compare with a polorotor option. I was refering to the situation when the dish is motorised and not limited to a single fixed satellite. as for the claims on cross plorisation - that remains what they are.

Bigger dish - can youbend the rails a little so that it fits or lift the dish above them ?


Regards

Old Satellite
 

Llew

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Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards.
Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
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#11
I found the SMW X-Line LNB used to wander in frequency with quite small changes in temperature when used for analogue reception. I had to constantly adjust the LO frequency of my Echostar SR8700. - the AFC pull-in range of the RX couldn't cope.This was after about 8 years constant use, so perhaps it was just ageing.
I'd be interested to know how you get on if you decide to obtain one for use with a digital receiver.

Llew
 

Likvid

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#12
Hmmm, strange, i know the X-line can be ordered so you get LO=+/-1MHz

I hate living in an apartment to be honest but i don't have any choice right now so i have to get the most out of this little system as much as i can.
 

Likvid

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#13
I've contacted Seavey Engineering now for a price quote.

Now is the question which SMW LNB i should get, the SMW WDL Digital or the SMW X-Line? i can't find out if there are any difference really as they seem similar on tech specs but differ in how they operate.

Too bad their PLL LNBs can't take the whole spectrum of 10.7-12.75GHz, i would have liked to try that out.
 

Likvid

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#14
Strange, they don't even answer, sent 2 emails now, either they are slow like hell or don't read their email at all.