can only get some satellites if approached from one direction

[Jim S.]

OK, this is a weird problem.

A few weeks ago, I had a problem where it looked like I wasn't getting any signal on 72w and 74w, but all satellites to the east and west of them were fine. Eventually, I found out that if I went east of them and then went back westerly to them, they worked. But approaching them from the west, no signal. I went out to look at the dish, and I found that the cable to the LNB wasn't screwed on tight, presumably from several days of wide temperature swings. So I screwed it up tight again, and things worked fine.

Now, I'm having the same problem again, but when I checked the cable, it was fine! I'm going to go out tomorrow when it's warmer and change the connectors, but meanwhile, has anybody had anything like this happen before? I'm hoping I don't have something rattling around loose in the LNB...

 

[putney]

could be that you have play in your motor (or linkage)

 

[Jim S.]

That's a possibility, though I'd have to think about it a while before I decided whether it makes any sense for it to only be affecting two satellites. Since I'm at 77 degrees longitude and 79w doesn't exist anymore, they're the two satellites closest to south for me. 83w works fine in either direction though.

 

[chaskuchar]

i am assuming that he would bump the dish either way so the motor would not be the problem. however, the linkage of the dish might move the dish up in one direction and move it lower in the other direction. i do find my receiver when it lock on to a transponder it will receive that signal even if i move the dish slightly off of center where it would not pick up the signal if that is where the dish was to start with. charlie

 

[Tron]

As Putney suggested, most likely this is caused by motor shaft slack. The slack can be adjusted, and there are various procedures involved in doing this depending on the motor you are using.

I've found the easiest motor to adjust slack, or backlash on is the SG-9120. Adjusting backlash on any motor involves breaking a seal that will void the manufacturer's warranty.

 

[Lone Gunman]

Jim it's a good idea to put what equipment you are using in your signature. That way PPL can see what you are using and therefore make a more informed suggestion as to what is causing the problem and how to fix it, and, then you won't have to list it every time you ask a question about it. ;-)

 

[Jim S.]

Yeah I keep meaning to do that and then I never get to it...

I have a PowerTech DG-280B motor. The manual claims that the backlash adjustment can be done with external screws. Not that I have a problem opening the motor, as it's out of warranty and I've already opened it anyway when it developed a stuck relay a few months ago, but I wouldn't want to have to take everything down and then re-align it in the winter.

I'm thinking I may let it go until spring anyway, as long as it's only affecting 72 (and 74 which should be gone anytime now). I wouldn't want to throw my alignment out on everything else and have to re-do it in the winter. Right now the tracking is spectacular on everything west of 72. It gets bad, backlash or no backlash, east on Hispasat, but I only have half a signal there anyway due to a tree branch I can't reach.

 

[Jim S.]

Well, something has got worse now. This morning I couldn't get 72W at all no matter what side I approached it on. So, even though it was below freezing, I went out and checked the dish. There was a visible amount of play in the motor tube. So, seeing as how the DG-280 has the backlash adjustment screw readily accessible, I tightened it up. But still no signal on 72W. Everything else to the west of south (I'm at about 77 degrees) is still spectacularly aligned, Hispasat is still there at its normal half-assed level, and I can even get one data transponder on 37.6. Just no 72! (61.5 is solidly behind a tree.)

I even tried bumping the position with DisEqC 1.2. (I use USALS for everything, since my motor alignment is good enough to do so.) No luck. No signal at all on 72. In fact, most of the time my strength reading is at 36%, which is Openbox-speak for "no signal", rather than 45%, which is Openbox-speak for "it looks like a transponder, but it won't lock".

Last night was the coldest night we've had this season so far, but if something had flexed in the motor mount or the J-tube, I wouldn't think I would still be having uniformly great alignment on the rest of the arc. I checked everything all the way over to 125 and it's still good, all the usual weak signals are coming in, Montana PBS, both SatMexes, the S2 on 103, even CBS Newspath. Everything back down through 83. That's a heck of a spread to be fine if something was that far off, I know, I've had poor alignment before.

The only thing I can think of is maybe the weight of the Invacom QPH-031 has something to do with it. Someday I should switch it back to a cheap plastic LNB again to see if it changes anything. I just don't like being out in the cold anymore. And I don't have a meter, so I'm definitely not hauling out receiver/monitor/extension cord til spring!

 

[Jim S.]

Good news, I got everything working again!

This morning I poked around with DisEqC 1.2 again til I got it to the point it was before -- working when coming up on 72 from the east, but not the west. Then I went out to the dish again, checked for slop again -- still none. Started turning coax connectors to make sure everything was still tight. This time, it was the one on the motor side of the 22kHz switch that had worked loose! Tightened it up and everything works fine again, even if I switch back to USALS. So, I had two problems at once -- the slop in the motor and the loose connection.

 

[turbosat]

I had that happen back in the early fall, was hard to believe that cable connector had worked so loose, it was almost ready to fall out of the motor! But then, its been through three very hot summers, last summer particularly, since I put that motor in. Just tightening up the cable fixed mine. Having two puzzles at once in the cold is tough.