Lnb L.O. Drift (Decades <--> H&I)

[TvMind]

Hello again, more Decades/H&I troubles

Ok I took the plunge and finally flashed my microHD with the June 6 th file (latest) to be able to receive all the channels that are closely spaced (4 khz) . This was supposed to fix the problem where Decades would suddenly start pixelating and turn into H&I, that is why I loaded this latest file, otherwise I never would have bothered as I was extremely happy with the Jan 1 file I have been for the longest time.

Now as I am recording the Dobie Gillis binge I noticed the same trouble and quickly caught it by temporarily going to the menu and back to stop the 'morphing'. I am an electronics technician so understand how drift (caused by increased temperatures here now) can cause the local oscillator in the lnb to cause the receiver some confusion - again the tight spacing of only 4 khz ! I have an older lnb and I am sure the specs are woefully out of range by todays standards.

Do you guys and gals think a newer Norsat will do the trick or should I do some more investigating.
If I get a chance I want to spray the electronics with refrigerant to see how much it fluctuates - later when I do some annual tune up work.

In the meantime enjoy the Binge !!

T

 

[Magic Static]

I have a similar issue with a PC tuner, but the Ist edition microHD has no issues with the same dish and Norsat PLL LNBs. I'm am going to say you are barking up the wrong tree here thinking it's a drift issue. But I'm no expert

 

[Titanium]

I have observed aging and/or failing DRO LNBFs drift 10MHz or more. More typical to observe 3-5MHz range. The micro was coded for +/-5MHz AFT. While this is great with a centered and stable LNB(f), it could be a problem with a drifting LNB on tightly spaced SCPC channel.

If you don't have access to a spectrum analyzer, try this simple test to determine if it is LNB LO drift causing the problem:
At one temperature extreme (cool or hot) delete the transponders and blind scan the satellite. Take note of the logged transponder frequencies for theses two channels. If you observe the problem again, delete the transponders and blind scan. Are the new transponder frequencies different? If so, by more than a 1.5MHz?

If you find the LNB is showing the effects of aging or thermal drift, you may want to update to a LNB(f) with more stability (available in DRO or a PLL for even tighter frequency stability).

 

[FaT Air]

That's actually 4Mhz difference. 3957Mhz 3.957Ghz 3,957,000Khz An older LNB could drift even more than that 4 Mhz.
I was going to say basically what Titanium just posted also. delete and Scan those TP's in an see a difference??

 

[yankee495]

Hello TvMind,

I've been around here for a while and drop in now and then but have't posted anything in quite some time. Around the time you posted this my Openbox S9, an old original started doing the Decades<>H&I channel surfing on its own. I haven't worked on a problem since I set this dish up in 2011 with the S9 so stability based on temperature didn't come to mind right off.

Mine is acting pretty odd and Movies! would do it once in a while then it pretty much cleared up. Back around 2011 there were a lot of junk capacitors that hit the market and my 2011 TV just started not wanting to turn on, so I've got some in it for certain. I was thinking I may have a capacitor problem but now I'm thinking I need to check the cables and connectors because I do get a small glitch now and then on METV which is rock solid all of the time. Maybe METV does glitch on it's own but it may be related.

I was glad to see your post and was hoping it was the signal, not the reception equipment. I did check the dish and the cables and cleaned them up a bit for good measure but they're really weren't dirty. As soon as I can I'll get out there and check everything, and the back of the box, and Vbox.

Editing the transponder from 3957 to 56, or 58 or whatever doesn't seem to help. I don't know why it cleared up but it worked for a while and then did it again, then worked, then did it again. I'm talking days apart with many temp changes too. Now it's bad and will drive you nuts glitching, but it doesn't change to H&I as much. It was changing before I could get back to the other room from doing the up/down channel to get it locked again. I have it split off to another room.

I have good ribbon cable and these seem the be the problem channels, but they just work when they want to and it doesn't appear to be temperature related. The feed is a DMX741 LNBF that's been awesome, never a problem. I didn't realize Decades and H&I were so close until I had problems, but again, it did work fine for ages so to speak. I know the feed could have problems, but it works when it wants to. I have noticed commercials don't glitch near as bad as the programming and a lot of the time not at all, that's weird. Yes, I have great commercials and as soon as the program comes back on, it stutters and may change channel.

I just wanted to explain what I've seen because it's odd indeed. I had assumed someone would say, it's just that way, we can't fix it, but that isn't the case I guess and it is working for others. Ok, I'll get back here and post what I find and I hope I didn't over look a posted fix or whatever. I do have 86S & 71Q, so it's a pretty solid signal. When it glitches it drops to 10S just wham, then back and it may be on the wrong channel. I'll let ya know.

 

[yankee495]

I think I found my problem. I noticed it was only doing it on windy days and I thought the acme nut may be worn. Sure enough, it completely stripped out 2 days ago. I have a clamp on the arm holding it on SES 1 and it's stable now. I'm working on repairing an actuator I have or just buying a new one. Check your dish for slop, it may be the problem with glitches which had became frequent for me and then it would switch channels.