LNB comparison tests

Originally Posted by snap

Hi, Here's another test. The weather has turned really wet and cold, so it's becoming more difficult.
I tried the three C120 Invacom LNB's against one another. The quad is the same as used previously.
It seems to bear out suspicions I've had before I got the meter. There's a quite a marked improvement when changing from the single to a quad, but only on weak 2D signals. The difference is beyond the normal manufacturing range found in these LNB's (note that each one is tested before it leaves Invacom, and has its test printout in the box).
The difference between the twin and quad is closer to call, and needs a greater number of samples. It still seems that the Quad is the one to go for. The particular twin used seems to be better on vertical TP's and also high band TP's.
The results for TP 24 (Channel Four) and TP 31 (FIVE) expose the limitations of the Wolsey meter and ought to be disregarded. The TP 4 (default transponder) seems to be accurate.
I've aslo posted some pix of my installation on one of the few dry days recently. Note the close up of the LNB. The plastic adaptor on the ChannelMaster feed is back to front, as I found there is higher gain to be had by increasing the distance from the dish to LNB. You have to be careful doing this, in case the feed starts to pick up interference from behind the dish. I think the F/D ratio on the Prodelin I'm using is very slightly different to the equivalent ChannelMaster, for which the feed is designed.

Originally Posted by snap

The one I fitted (invacom) had a 'Optimised for HD' sticker on the box.

Originally Posted by snap

No, I never got round to testing the Inverto.
The result for vertical 2D using a twin is what I read off my meter, it may be correct, but the difference is small.
Since I did this test the quad I used was hit by lightning and destroyed. The one I replaced it with was significantly better on 2D horizontals. Invacom made some kind of modification about a year a go. The one I fitted had a 'Optimised for HD' sticker on the box. No one really knows what this means, apart from Invacom.

Originally Posted by snap

a fraction of a mm can make SQ jump from zero to way up the scale.

Originally Posted by koansrc

A fraction of a mm ?

That is figure of speech isn't it ?

Originally Posted by Prodelin

Don't put serial numbers out on a public forum

Originally Posted by snap

I may have a WR 75 feedhorn in my parts box in Madrid, which you are welcome to have. I'll have a look on my next visit.
The WR 75 feeds came as standard with Prodelin dishes in Spain, and are useless for standard LNBs.

Originally Posted by snap

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?

Originally Posted by artafernes

Although this message is old I am assuming this thread is still alive, since I received a link through my e-mail just yesterday, so here goes my question: I live in Madrid and I managed to get an official subscription to sky which I pay regularly and I indeed had a channel master dish with a sharp lnb installed by an expatriate installer; I must say that I have read often about good lnbs for fringe reception but never decided to take the jump and install for example an invacom mostly for fear of not being able to install it myself and not knowing a reliable installer to do it. If the difference is so appreciable, specially with the BBC, I think I would go for it so, is it really worth it? any help locating a reliable installer on the norhwestern suburbs of Madrid?
Thanks in advance for any help.