poor performance from Invacom SNH-031

[Jim S.]

I've been using a WSI DMX-521 LNBF for quite a while and I've had no complaints about it, but when I saw an Invacom SNH-031 on eBay for less than the retail price, I jumped at the chance to try what's supposed to be one of the best LNBFs available. After all, everybody says that the specs on the DMX models aren't accurate, whereas Invacom's are, so I expected a big increase in signal quality on problematic transponders.

I installed it tonight and tested it first on SES-1, since that's where my dish happened to be pointing. I had had a quality reading of 71 on my Openbox on the BVN transponder with the DMX-522. With the Invacom, I got a quality reading only in the 50s. I scanned the satellite and got all the channels I expected to, but all at lower quality. So, I moved over to Galaxy 19, which isn't as strong as SES-1. I only got a few transponders on that satellite instead of the 20-some I usually get. So, that ruled out weather or trees or anything blocking my line of site.

I tried moving the LNBF forward and backward in the holder, but I only got a slight change in signal quality no matter where I moved it, and mostly downward rather than upward.

I've read about Invacom's LNBFs causing feed arms to sag because of their thick metal casings, but my dish is a GeoSatPro 90cm with the feed support arms installed, so I don't think the arm is sagging. I thought about the possibility that the whole dish could be sagging on the pole, but I don't think that that's happening to any noticeable degree, because I used to have a Dish Network LNBF mounted alongside my FTA one and that's a fairly heavy unit in its own right, plus my dish moves further than that when the wind blows without the signal going down that much.

So, do you think I have a bad LNBF? It was supposed to be new, but it appears to have been used because there are a few dirt spots on it. I've heard about Invacom clones, but I don't think this is one because it has a hologram sticker on it -- although there was no hologram sticker on the box.

 

[sergei]

I not sure if all the information below will apply to you , but maybe it will as it came from a posting on the Sadoun back in 2005 when someone else was having the same problem.

SNH-031: Make sure your LNBF setting say UNIVERSAL1
L.O. Freq: 9750/10600
22KHz: ON (auto)

for the QPH-031:
For the LP side: Make sure your LNBF setting say STANDARD
L.O. Freq: 10750
22KHz: OFF

For the CP side: Make sure your LNBF setting say STANDARD
L.O. Freq: 11250
22KHz: OFF

 

[Jim S.]

I set it to 10600 with 22k on in order to avoid scanning empty spectrum on North American satellites. I can't imagine this would make any difference in the signal level vs. setting it to 9750/10600.

 

[turbosat]

could the skew be off, or can it be adjusted as it is now?

 

[Jim S.]

Skew is set at 0 by the markings on it, and a look inside the LNBF (it has a clear front cover) reveals that the probes are oriented correctly.

I found one post on here where someone said that an Invacom quad-polar LNBF caused their holder to sag! I doubt that this model is as heavy as the quad, but that's something I'll have to check next time I have time to tinker with it. For now, the DMX is back on so I can watch TV.

 

[zamar23]

Why don't you try Sergey's suggestions and see what happen - it includes 22kHz ON. Also keep in mind, durability and stability are extra factors, when comparing Invacom to other brands. Generally, Invacom in my experience seldom gives too high signal Q on Linear TPs, and its clone is no different in performance from genuine LNB. But you may have a used & returned defective LNB as well.

 

[pendragon]

Something is very wrong if you're only getting a few TPs on G19 with a 90 cm reflector. For the signals you've mentioned, I would not expect to see much improvement with the Invacom, but certainly you shouldn't take a performance hit. The benefit of the Invacom will tend to be more noticeable on high FEC 8PSK and higher order DVB-S2 modulations.

I presume you've verified both in-track and cross-track alignment off your dish with the Invacom? Different LNBFs can require minor dish adjustments in addition to LNBF positioning tweaks. If that's not the case perhaps your Invacom is indeed faulty or phony. The only other possibility is Invacom LNBFs generally have lower gain than garden-variety units. If your distribution path has significant losses, this may impact the Invacom quality readings more than your existing LNBF. You can test this by connecting your receiver at the dish, and if true this would easily be solved with an in-line amplifier.

 

[Jim S.]

I haven't had time to do any further testing. I had done my tests yesterday without moving my receiver and monitor outside, and I don't have a satellite meter, so I was limited in how well I could test. Moving the LNBF toward and away from the dish was easy, but without having the quality reading in front of me, I couldn't lean on the edges of the dish to check the north-south and east-west alignment.

 

[AcWxRadar]

Hi Jim S,

The WSI DMX-521 may be a "perfectly" tuned match for the 90 cm dish and its specific f/d ratio that you are testing whereas the Invacom LNBF might be better matched to a different dimensioned dish. This factor may account for some deviation in the quality readings. I would expect to see up to 2% difference solely because of this factor in an ideal situation.

Next, I could imagine up to 1% deviation in quality just due to mechanical alignments (those that are under your control) like the physical orientation of the LNBF.

I would also stipulate the difference in quality of the actual LNBFs (S/R ratio parameters etc) between the two brands/models. I would be liberal to expect up to 3% change in signal quality reading to the actual ability of the LNBFs.

However, this all adds up to only 6% difference and I honestly cannot logically say that I would expect this under most normal circumstances.

I am therefore extremely suspicious that something else is a factor. In order for you to detect a 21% difference in quality and even lose some TPs from your listings, there MUST be something else that is accountable for that large of an error margin.

Is the QNH-031 really that BAD? Or did you receive one that is deficient in quality for some reason? Hmm? I just cannot fathom the 21% difference right off the bat. That is just too much for me to justify, unless it truly is a POS.

Here is an older thread on the same LNBF:

http://www.satelliteguys.us/free-air-fta-discussion/63434-unhappy-invacom-snh-031-lnbf.html

Another factor might be the signal/quality meter of the OpenBox. That might account for some of this error. Maybe its Q scale is not very linear and it falls off faster?

I also am a little skeptical about your quality reading on SES 1 (with your original LNBF). I think you should see a higher Q reading, but that depends upon which TP you are looking at. I assume it is 12060 HOR, but you could have been looking at some other TP, but it also might just be due to your OpenBox meter scaling.

I have an INVACOM QPH-031 on a 1.2 M dish and looking at TP 12060 HOR on SES 1, my AZBox Q meter is maxed out (100%). If I want to test the C/N reading properly, I would use my SuperBuddy meter instead of my AZBox built-in meter. If you are interested, I will test your QNH-031 against my QPH-031 and get readings from my SuperBuddy. If you pay to ship it to me I will pay to ship it back to you when I complete the tests. That's just for our amusement and only if you are interested. I just thought I would offer that..... You have me curious, now!

PM me if you are interested in that testing option.

Otherwise, I just cannot see the QNH-031 LNBF being that bad. It very well could be.

RADAR

 

[Jim S.]

Thank you for the generous offer of testing. However, considerations of what might or might not be wrong with the Invacom are on hold for the moment, as even my DMX LNBF now seems to be losing transponders in just heavy cloud cover. It never did that before. Probably the dish is out of alignment. But the disturbing thing is that I'm not getting transponders from adjacent satellites like I do if it's rotated on the pole. That means that either the elevation has slipped somehow, which I dread trying to fix because the dish will try to move when I loosen the bolts, or worse, the pole is leaning I was hoping to work on it today, but it's raining.

 

[Jim S.]

Well, I'm happy to report that the Invacom works at least as well as the DMX! I haven't had time to test it thoroughly to see if it works better, although it should.

My problem was that the dish had indeed slipped down on its elevation bracket somehow. Moving it back up not only fixed my signal quality on all the satellites I was getting, but also tightened my tracking up enough that I'm now getting Hispasat, which I had previously thought was behind a branch! (On the other hand, I lost a few transponders on 125W, unless IT'S behind a branch now. But my time and patience ran out. If I don't check it before then, I'll find out in the fall.)

 

[Anole]

That means that either the elevation has slipped somehow, which I dread trying to fix because the dish will try to move when I loosen the bolts,
.'.'.'.'.'.'.'
My problem was that the dish had indeed slipped down on its elevation bracket somehow.
Moving it back up not only fixed my signal quality on all the satellites I was getting, but also tightened my tracking up...

Is it my maybe time to consider a fix?
I think the Fortec 1m and 1.2m were pretty touchy.

There have been a lot of very imaginative ideas here on the forum for tuning the elevation, over the years.
Some included a bracket and large screw.
Some used a turnbuckle.
And there were many more . . .

 

[AcWxRadar]

Well, I'm happy to report that the Invacom works at least as well as the DMX! I haven't had time to test it thoroughly to see if it works better, although it should.

My problem was that the dish had indeed slipped down on its elevation bracket somehow. Moving it back up not only fixed my signal quality on all the satellites I was getting, but also tightened my tracking up enough that I'm now getting Hispasat, which I had previously thought was behind a branch! (On the other hand, I lost a few transponders on 125W, unless IT'S behind a branch now. But my time and patience ran out. If I don't check it before then, I'll find out in the fall.)

Jim,

I personally thought your results were a bit suspicious. The 21% signal quality difference was just too much for me to buy or explain. Now, you have found a discrepancy with the DMX LNB operation, so it boiled down to your alignment after all. Don't worry about it too much, but you do need to be careful to avoid jumping to false conclusions. Sometimes we all get in a hurry to present our findings and we are wrong. It's not a big deal, really. We are all trying our best and have good interests at heart, we may just get a bit ahead of ourselves at times. I won't knock you for that, I have jumped to the wrong conclusions myself before. Just consider it as a very good and very valuable learning experience. You learn much more from a mistake than you learn from a success. This is very true. And, you know that here in this forum we all understand this. No one here will give you a bad time for anything... right or wrong. If we have to argue a point, I think we do so very well. Diplomatically and sincerely open and honestly.

Now, for your situation, you just have to figure out your alignment trouble. That won't take you too long.

RADAR

 

[Jim S.]

So far, from the limited testing I've had time to do, the Invacom is working great. It does seem to hold the signal a little bit better on transponders I was having problems with before, even before my dish got out of alignment.

But there's one weird thing that I didn't expect from what's supposed to be a high-precision LNBF: the transponder frequencies I get on a blind scan are all from 2 to 5 MHz higher than what I had before. If it was just different from what my old LNBF was getting, I'd think the old LNBF was off-frequency, but they're all, 100% as far as I've seen so far, 5 MHz higher than what TheList and LyngSat have listed as well, whereas the old LNBF would be closer on some.

Other than the fact that it doubles my channel list if I don't clean it out before doing a blind scan, I've also had to manually increase the frequency on transponders that I've had to manually add originally since the Openbox missed the low symbol rates, such as Telemundo on 79.

I wonder if it's the Openbox that's off-frequency and not the Invacom.

 

[ACRadio]

But there's one weird thing that I didn't expect from what's supposed to be a high-precision LNBF: the transponder frequencies I get on a blind scan are all from 2 to 5 MHz higher than what I had before.

I have an TWF-031 that is the same way...10600 is 5 Mhz off and 9750 is about 3. You can tweak the slugs inside the cover and fine tune the oscillator frequency but I haven't got around to doing mine yet.

 

[Anole]

Think maybe it was dropped?
I'm sure they were set accurately at the factory.

 

[freezy]

Chainsaw

 

[Tron]

My QPH-031 has no better L.O. stability than an average Ku-Band LNBF. Looking at the specifications, it is +/- 1 MHz, which is common for the LNBFs sold to FTA hobbyists. Sounds like the drift may be more than that, though.

I don't remember whether the universal models had similar specs or not.

 

[Hindu55]

"on a blind scan are all from 2 to 5 MHz higher"

I have two of the TWH-031 models and they are both off frequency just like yours.
Bought the second one because of that and the new one was the same. Don't
have that problem with the QPH-031. I came to the conclusion that it's because
the universals cover such a wide range.

 

[Jim S.]

I have an TWF-031 that is the same way...10600 is 5 Mhz off and 9750 is about 3. You can tweak the slugs inside the cover and fine tune the oscillator frequency but I haven't got around to doing mine yet.

Since I don't have any test equipment, I don't know how I could adjust mine though. I don't think the meter on my receiver would cut it, since I can receive wide transponders at either the "old" or "new" frequency. I don't know whether I could manage it with a narrow transponder that only locks at one frequency or whether the meter would still be too coarse of a scale to do the job properly.

It would be nice if I had a receiver with a user-specifiable LO frequency. Maybe I should ask Brian at SatelliteAV if they can put this in whatever they're working on...

By the way, what are you picking up on the low band? I don't have LOS to too many of the Atlantic satellites, but the ones I think I do that I've tried so far, I've found nothing. The listings on LyngSat are all very old and the listings on TheList aren't dated, so maybe they're all gone.