Thread: Signal great at dish, but not at receiver

Not sure if this is the proper forum. Please let me know where I should post if not here.
I get a Ku band 11.7-12.2 GHz feed for our radio station.
We use a PLL LNB. My dish drifted some from rapidly changing temperatures here in Columbus, GA and the signal was degrading enough to occasionally drop out. I have a Digisat III Pro meter.
So I put the meter on the dish and got her aimed up well, Reading went from 99.5 to HI. That was nice. Go back to the head end, about 75 yards away, and no joy on the receiver. So I put the meter on there and it says I have nothing coming from the LNB, even though the cable is supplying 18.x volts when I meter it at the dish.
Put a new connector on even though that could not be the problem, ( to my non-engineer mind, anyway), We put the cable in in last July or so, a single run- no splices- and all was well till the weather made the dish lose alignment.
I cant understand why the cable is good both ways and fine one day, but the next it seems fine when metered at the dish but no signal is there when I meter at the receiver.
The meter is plainly marked which is the LNB side and which is the receiver and I made sure I was not fouling that up. The signal at the dish is still 99.x to HI and looks like it ought to be kicking it real good. The recent solar flare didn't affect the bird, so the source tell me, and if it had I would not have got the 99.x to HI on the meter, right?
Whaddya yall reckon?
Any help would be greatly appreciated

Originally Posted by stiche

Not sure if this is the proper forum. Please let me know where I should post if not here.
I get a Ku band 11.7-12.2 GHz feed for our radio station.
We use a PLL LNB. My dish drifted some from rapidly changing temperatures here in Columbus, GA and the signal was degrading enough to occasionally drop out. I have a Digisat III Pro meter.
So I put the meter on the dish and got her aimed up well, Reading went from 99.5 to HI. That was nice. Go back to the head end, about 75 yards away, and no joy on the receiver. So I put the meter on there and it says I have nothing coming from the LNB, even though the cable is supplying 18.x volts when I meter it at the dish.
Put a new connector on even though that could not be the problem, ( to my non-engineer mind, anyway), We put the cable in in last July or so, a single run- no splices- and all was well till the weather made the dish lose alignment.
I cant understand why the cable is good both ways and fine one day, but the next it seems fine when metered at the dish but no signal is there when I meter at the receiver.
The meter is plainly marked which is the LNB side and which is the receiver and I made sure I was not fouling that up. The signal at the dish is still 99.x to HI and looks like it ought to be kicking it real good. The recent solar flare didn't affect the bird, so the source tell me, and if it had I would not have got the 99.x to HI on the meter, right?
Whaddya yall reckon?
Any help would be greatly appreciated

Have you tried using a new cable, instead of the one you have there now?

I vote for bad coax. DC is easy to send down the coax. 1Ghz rf is not as cooperative. Water infiltration somehow is my guess. Split insulation or a pinhole will do it.

3rd vote on bad coax

Check the length of the center conductor of the coax. The "stinger" should only extend past the fitting by approximately 3/16". Too short or too long....... both could cause issues.

Check inside the LNBF f-fitting connector. Sometimes these pinch points are bent and can not make contact with the coax cable's center conductor. The jumper cable that you are using at the dish may contact these pinch points with the center conductor, but the installed coax cable might not make contact.

Try taking sand paper or a womens emery board to the center conductor of cable at both end of the cable to clean up the copper.

Good luck

Thanks for all the tips. We actually ran a double run of coax when we pulled the cable, so I have two coax runs that I tried, with exactly the same result. I learned coax install in the 70's doing cable tv and was taught to always scrape the center conductor to get shiny copper for the connection.
The too short or too long center conductor may be my issue, so I guess I will try that today. I wonder if the LNB may be the problem. We have replaced the LNB 4 times in as many years. Does that sound normal?
Does everyone else's plant drive them as crazy as mine does me? Haw-Haw! The thing goes along so well for months and then has all sorts of weird problems.
Like I said, I am not a trained engineer, but have picked up things over the years from having to be the one who maintains the plant since our non-profit is so poor-at least that's what they keep telling me....

LNBs, especially expensive ones like the one you're using, are seldom the problem. If the LNB has required replacement once a year, something is definitely killing your LNBs. I would be suspicious of bad DC on a power inserter or other equipment connected to the cable.

Is the dish properly grounded?

Stiche,

You stated that you checked the signal with the meter at the dish and then at the receiver. Surely you didn't use the full 225 feet to go straight to the receiver? You surely must have installed a ground terminal block near where the cable enters the house and then some sort of a wall termination for an outlet near the TV. Didn't you? If you did install these, try checking the signal on the antenna side of these connections. If the signal is good for both of the cable runs you made at these points, then it is a problem with the cable leading into the house to the receiver.

Another possibility, what type of cable did you use? RG-6 could possibly function at that length, but I would have used RG-11. I have about 280 feet between the antenna and the receiver (at least) and I couldn't use RG-6 for this. I lost most all of the signal and I had a lot of trouble driving my motor, switches and powering the LNBF. So, I am wondering if over time and with weather changes, the cable hasn't simply degraded enough to cause you trouble (especially if any moisture happened to get into the cable jacket). This could possibly explain why both cables are presenting similar symptoms. Of course, that is reaching a little.

Let's see, what else? How about any cable routing which resulted in a bend with too tight of a radius? This can damage a cable and since you ran two cables, they probably are both routed in the same fashion so would have the same bends. That would damage the insulating core around the center conductor.

RADAR