LNB comparison tests

[dxsat]

Like many people, I have become baffled and annoyed by conflicting reports on which LNB is better for fringe reception. I decided to run a series of tests for myself, and try to do them in as thorough a way as possible. Some forum members are actually selling the LNBs they recommend, through their online shops...
Here is the first test, on the Invacom Quad C120LNB, used extensively in weak signal areas. There is an ongoing discussion amongst the Cyprus members as to whether there is any difference between the four ports on the LNB.
As you can see from the charts, there is a measureable difference, but only on horizontal high band. On Vertical high band, the outer two ports seem to have the edge. On low band, as used by Astra 2D, the margin between the ports is smaller.
The tests were carried out on 13th October 2006 at 17.00 hours CET, using the new Lacuna / Wolsey Satmeter 3. The LNB's were fitted to a 1.8 metre Prodelin offet fibre- based dish, with a ChannelMaster Feed. Skew is 24 degrees.
All strength bars are out of 10
The meter has two signal strength (SS) bars, the first a crude measure, the second one much more sensitive. Picture quality is as you would expect, with an addition numberic value, which I've included.
The Wolsey meter needs to be calibrated to the conditions you are working in.
The next test I run I'll use an equal calibration value. (Calibration is just another way of turning up the sensitivity.)
I used three Quads from the same batch, to get a reliable result.
Coming next.. Extreme threshold test: Sharp v. MTI v. Invacom ...the results were surprising, and there was a clear winner

 

[spiney]

Note that, lnbs vary, between different batches!

The manufacturer specs - especially gain - will say "typical".

Also, apart from pixelation, "picture quality" means absolutely nothing.

 

[Llew]

Like many people, I have become baffled and annoyed by conflicting reports on which LNB is better for fringe reception. I decided to run a series of tests for myself, and try to do them in as thorough a way as possible. Some forum members are actually selling the LNBs they recommend, through their online shops...
Here is the first test, on the Invacom Quad C120LNB, used extensively in weak signal areas. There is an ongoing discussion amongst the Cyprus members as to whether there is any difference between the four ports on the LNB.
As you can see from the charts, there is a measureable difference, but only on horizontal high band. On Vertical high band, the outer two ports seem to have the edge. On low band, as used by Astra 2D, the margin between the ports is smaller.
The tests were carried out on 13th October 2006 at 17.00 hours CET, using the new Lacuna / Wolsey Satmeter 3. The LNB's were fitted to a 1.8 metre Prodelin offet fibre- based dish, with a ChannelMaster Feed. Skew is 24 degrees.
All strength bars are out of 10
The meter has two signal strength (SS) bars, the first a crude measure, the second one much more sensitive. Picture quality is as you would expect, with an addition numberic value, which I've included.
The Wolsey meter needs to be calibrated to the conditions you are working in.
The next test I run I'll use an equal calibration value. (Calibration is just another way of turning up the sensitivity.)
I used three Quads from the same batch, to get a reliable result.
Coming next.. Extreme threshold test: Sharp v. MTI v. Invacom ...the results were surprising, and there was a clear winner

Very good, snap. I'm sure these findings will help people who live on the fringe of the footprints.

Llew

 

[bignick]

Thanks for your efforts m8

Should the last sets of test results on each page read Horizontal Low Band and not Horizontal High band as they do right now? I only notice because they are of most importance here 2

Cheers & keep up the good work

Nick

 

[rato]

Thanks for the contribution. These findings are very helpful.

 

[Topper]

Whilst picture quality may or may not mean nothing, provided the same parameters are applied to each individual test then to some people it has a meaning as it is a way of assessing what lnb and parameters will give the specific results indicated, it doesn't matter what you call it. It is far more meaningful than having no assessment at all Well done

 

[dxsat]

Thanks for your efforts m8

Should the last sets of test results on each page read Horizontal Low Band and not Horizontal High band as they do right now? I only notice because they are of most importance here 2


Nick

OOps..Quite right, I'll amend that a.s.a.p. The bottom row on each LNB test page should read Horizontal Low Band.
Just shows a second pair of eyes is extremely useful.

 

[dxsat]

Note that, lnbs vary, between different batches!

The manufacturer specs - especially gain - will say "typical".

Also, apart from pixelation, "picture quality" means absolutely nothing.

I also tested the ports on the Quad Invacom LNB which has been on my dish for some months, from a different batch, but didn't keep a written note. I remember the results being very similar.

I appreciate what you mean about 'picture quality' being subjective, but in this case I was measuring bit error rate. The Wolsey meter uses the abbreviation 'PQ' rather than 'BER'

 

[ouagadougou]

Well done Snap, at least someone is making the effort to test and post some results. Just ignore any negative comments about measurement validity as anything is better than nothing and quality/BER is a good comparison as long as its the same meter being used each time.

As long as people understand variability between LNB's of the same type then your results are a big help especially if you can post comparative results of changes to your system as you say you plan on doing.

Cheers.

 

[spiney]

Well done Snap, at least someone is making the effort to test and post some results. Just ignore any negative comments about measurement validity as anything is better than nothing and quality/BER is a good comparison as long as its the same meter being used each time.

As long as people understand variability between LNB's of the same type then your results are a big help especially if you can post comparative results of changes to your system as you say you plan on doing.

Cheers.

There were no negative comments from me, I was just pointing out the obvious pitfalls, whether it's worth doing at all is a different matter!

Because the particualr lnbs tested will be from different manufacturer batches, there's no way of directly comparing them, unless you test a large number, across the batches, to get a result that's statistically significant. That's impractical, and also why magazines like What Satellite etc don't do it either.

The unit tested is most probably - but deosn't have to be - in the median range, and some idea of the parameters spread would be useful, as given in manufacturer data sheets. Presumably, higher cost units have better quality control, hence less variability, one reason for the huge price differences in "low noise" types.

"Picture quality" is meaningless, if you meant signal quality as a relative value then that's not much better without some idea of what it means, really the BER is needed.

I don't want to be a killjoy, but you are making a general recommendation, after testing only a very few samples

 

[ouagadougou]

I think publishing test results that show the variability in perfomance across a batch of LNB's of the same type is well worth doing. I personally dont believe many of the parameters published with these mass market LNB's especially Noise Figure and I think everyone else should treat them with caution as well.

Whatever results Snap publishes are an indicator but not a gaurantee but I would still rather have that indicator and his tests seem to have been done in a logical and controlled way so well worth publishing in my opinion. Comparative testing of improvement or not on your own system after changes is still the best way in our hobby environment unless you have the ability to really measure system noise temperature.

 

[spiney]

Yes.

It's great of Snap to do this.

The only snag is, you might get a very good example of one brand, and a very bad example of another.

There's no way anyone is going to do "across batch" tests, unfortunately, so we're reliant on manufacturers being honest with data!

There's also the matter of waveguide horn matching. "Sky" lnbs are usually optimised for minidishes, but are all feedhorns (without flanges added) identical? You might get different results by "optimising" in each case!

Sorry, there I go again, pouring more cold water ........


(added) here's a typical inexpensive lnb spec sheet - ok, its for USA reception but that's irrelevant - look where it says "conversion gain", I'm afraid that's fairly typical! You can "expect" a randomly picked one to be at the middle of this range, but it just might be at either extreme end!

-http://www.newskies.com/lnbspecifications.htm

 

[dxsat]

Thanks for the last comments Spiney. I'd thought of the feedhorn variable, so in this new test I tried an Invacom with the oher commonly available offset feedhorn made by Gibertini. It is designed for an F/D ratio of 0.66. ChannelMaster and Prodelin do not publish the ratio of their dishes (I ought to go out and measure my dish, but it's raining hard)

I found that a ChannelMaster feed worked better on both the 1.2 and 1.5 Gibertini antennas.

The results confirm many anecdotal comments in forums over the past few years. The most commonly recommended LNBs have been MTI BlueLine and Invacom, and these tests confirm this. I only had one BlueLine to try, and I had to use it in an installation before the night-time testing, which was a pity. I had four MTI white 0.2 examples, they were all very similar, much worse than the BlueLine single 0.6 (so much for manufacturer's noise figures!).
The MTI BlueLine single was better than the twin. The MTI twin's rear port was better than the front.
What was really surprising was the poor performance of the Sharp 0.3. It was so bad I thought I had used a duff unit, so I went through the others on my box. (I've been removing these from customers' dishes for the past year, replacing them with Invacoms) See second attached image for another test on six Sharp 0.3 LNBs.
No Sharp LNB could produce a lock on 10773 H BBC transponder at 10-30pm. They varied quite a bit on vertical TP's, as you can see. They perform OK in the daytime but fail dismally to hold a signal when it weakens in the evenings (when most people want to watch TV)
It is hard to replicate a very weak signal by covering up part of a dish. I tried this and my meter went crazy. In this part of Spain, horizontal TPs are VERY weak late evening.
It's worth saying that Sharp is very popular in Spain amangst expat installers, no doubt because the trade price is so low (about £10), whereas Invacom and MTI are the most expensive. Draw your own conclusions. For me, installing one of these on a ChannelMaster is like putting a Reliant Robin gearbox in a Porsche.
I chose 5 transponders, a mix of hi and lo, V and H. I think the problem with 12304 H, FIVE, is that there is interference from adjacent transponders, not that it is particularly weak.
On my dish with the reference Invacom I get all channels all day in wintertime. In summer BBC2 can start to go about 11pm. Recently, since 10th October, sun outage day here, the 2D signal has been markedly stronger.
I intend to run this test again when I have bought some more MTI BlueLine, to get a night-time result.
In this test I have drawn a threshold line to represent a clear picture. I had a Pace 2600CI (since sold) alongside a Pace Sky+(TDS470n- same tuner as 430n) on the same LNB to try to get an idea of the level of signal each needed. You'll probably be aware already that the 2600CI has a lower threshold. On the scale my meter produces, the 2600 needs 33/4 or value of 85 to be clear, the 470n needs 41/4 or value of 86.
Calibration was set to 030 on the Wolsey meter.
For some reason I don't understand, the breakup threshold is lower on high band. Is this due to the frequency or the different data rate and error correction?

 

[iceman]

What was really surprising was the poor performance of the Sharp 0.3. It was so bad I thought I had used a duff unit, so I went through the others on my box. (I've been removing these from customers' dishes for the past year, replacing them with Invacoms) See second attached image for another test on six Sharp 0.3 LNBs.
No Sharp LNB could produce a lock on 10773 H BBC transponder at 10-30pm. They varied quite a bit on vertical TP's, as you can see. They perform OK in the daytime but fail dismally to hold a signal when it weakens in the evenings (when most people want to watch TV)

I am afraid i have to disagree with you on this one M8...The whte case 0.3dB Sharp gives me better results than anything else i tried on my 1.5 offset Jonsa and 1.8m offset Azure Shine dish...I have replaced all the previously used invacoms on these dishes with 0.3dB Sharp LNBF...
But i suppose you have to take into account the fact that 1.5m & 1.8m dishes are not used for low band freqs 2D uses in this part of Mediterranean.
Sharp gives me a 24/7 lock on channel 4 using a 1.8m offset neither of the invacoms come near locking on this transponder..

 

[dxsat]

Hi Iceman,
You can see from the chart that the Sharp performs very well on Channel Four here as well, but what is beyond doubt is that it is very poor in Madrid for low band as used by 2D. In your location, all channels are weaker as you are further east than us. Here the south beams are extremely strong and are surely the cause of the cross-modulation problems that the Sharp deals with poorly.
What I didn't mention before is that the Sharp also has problems in Madrid on high band as well, typically losing Sky Movies 1-3 and 4-6 in the afternoons.
I think what this all means is that it depends on location and the relative stengths of channels.

 

[spiney]

This is difficult stuff, and snap is doing a great job, I think, as far as anyone can!

Unfortunately, we're never going to get "definitive" tests - across different manufacturers and batches, under lab conditions - in lieu of which, this type of info is the best currently available. Useful, I'm sure, to people trying to get any sat reception "on the fringe", including Sky in Spain.

 

[park_gate]

Snap is doing a great job but the problem is he is going to produce the definitive answer for Madrid!

If you are in a different area of the world (or even Spain) then you might find a different set-up applies for you.

You need an LNB with a low noise figure to work with weak signals but you need an LNB with a high third order IP if you have a large adjacent signal. There is normally a trade off between these two parameters so the right LNB will depend on how weak your 2D is and how strong your south beam is.

Does anyone think it is possible to use a low noise figure LNB in an area like Madrid and then some how reduce the amplitude of the south beam to avoid overload? Could this be done by using an adjustable / modified feed horn?

Also could it be possible to buy a load of LNBs on a sale or return bases then screen out the good ones for use in fringe areas?

Terry

 

[Topper]

Welcome to the forum park_gate

Snap is doing a great job but the problem is he is going to produce the definitive answer for Madrid!

Lol are you going to pay for him to relocate and repeat the tests?

If you are in a different area of the world (or even Spain) then you might find a different set-up applies for you.

On the next street the situation can be different so what is new

You need an LNB with a low noise figure to work with weak signals

Yes but values claimed differ between manufacturers as they all have different methods of measuring them so it is not possible to assess what is a good one it is trial and error

Does anyone think it is possible to use a low noise figure LNB in an area like Madrid and then some how reduce the amplitude of the south beam to avoid overload? Could this be done by using an adjustable / modified feed horn?

Whatever solution you applied e.g. a 3db filter it would affect all signals not just the south beam unless someone knows something I do not

Also could it be possible to buy a load of LNBs on a sale or return bases then screen out the good ones for use in fringe areas?

You would have to contact some manufacturers for an answer to that

 

[Likvid]

Also could it be possible to buy a load of LNBs on a sale or return bases then screen out the good ones for use in fringe areas?

Terry

Not possible, it would be like walking into a candystore and tell the owner of the shop you would like to taste all his candys and if they are good or not.

When you buy from manufacturer you buy in quantities, the minimum is often 50 pcs.

But most often you need to buy 200 pcs as there is no money in it otherwise for the manufacturer to make and single units you can buy from your local satshop.

 

[Rd100]

I agree with you the sharp 0.3 is the best lnb-f i have used

I am afraid i have to disagree with you on this one M8...The whte case 0.3dB Sharp gives me better results than anything else i tried on my 1.5 offset Jonsa and 1.8m offset Azure Shine dish...I have replaced all the previously used invacoms on these dishes with 0.3dB Sharp LNBF...
But i suppose you have to take into account the fact that 1.5m & 1.8m dishes are not used for low band freqs 2D uses in this part of Mediterranean.
Sharp gives me a 24/7 lock on channel 4 using a 1.8m offset neither of the invacoms come near locking on this transponder..