Signal great at dish, but not at receiver (1 Viewer)

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stiche

Thread Starter
New Member
Jan 26, 2012
2
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Phenix City, AL
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
 

Babadem

SatelliteGuys Pro
May 21, 2007
2,293
160
MA
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?
 

FaT Air

HOA Free Zone
Feb 27, 2010
6,668
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97W 48N
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.
 

SatelliteAV

SatelliteGuys Master
Lifetime Supporter
Sep 3, 2004
6,486
183
Roseville, CA
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.
 

ken2400

SatelliteGuys Pro
Sep 4, 2004
1,279
131
Central NY State
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
 

stiche

Thread Starter
New Member
Jan 26, 2012
2
0
Phenix City, AL
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....
 

Tron

SatelliteGuys Master
May 6, 2005
6,599
33
Metro New Orleans, LA
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?
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
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
 
Last edited:

markbone100

SatelliteGuys Pro
Jan 15, 2011
319
8
IL
Optimal bending radius of Rg6 should be no less then 5 inches, 8 for Rg11. But 75 yards with rg6 is pretty extreme.

Loss at 1000mhz with rg6 is 6.55 db per 100ft, while rg11 is 4.23 db at 100ft. Runs over 250ft for optimal signal results should use flexfeeder to miminize loss
 

Bob2011

SatelliteGuys Pro
Jan 5, 2011
526
2
Hudson Valley NY
I think people here are missing the point that it was working right before he disconnected it. I highly doubt something happened to two strands of cable at that instant. It is most likely a problem with the connector at the LNB like SatelliteAV described above.
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
I think people here are missing the point that it was working right before he disconnected it. I highly doubt something happened to two strands of cable at that instant. It is most likely a problem with the connector at the LNB like SatelliteAV described above.

Sorry Bob, but I think you may have missed the pertinent portions of the problem. He installed two very long cable runs last July and everything was working fine until recently. It finally got bad enough for him to investigate and he tried the second cable and it proved bad, too. Either both cables have degraded over time and with the weather or the problem lies elsewhere.

I vote on the problem being elsewhere right now, but the long cable run is not helping the situation. I suspect that there is either a ground terminal block or a through-wall connector that is poor. However, since the signal took a long time to degrade to being a detectable problem, it was not something that he did. From the description, it was working and started to develop problems and then progressively became worse. Then he tried the second cable run for a troubleshooting exercise and the problem still existed.

Unless both cables (which are far too long for RG-6 in this case) have failed, the problem lies elsewhere. But, we don't know that, even if we suspect so because we are not privy to all the pertinent information. We need more supporting information from the troubleshooting process.

The length of the extension of the center conductor is not likely to be an issue here. Although I would not rule it out, you must consider that it was operational and has recently ceased to be so. Sounds quite indicative of a poor connection steadily getting worse over time. The owner of this equipment was wise enough to install a secondary or redundant cable from the dish to the house for the longest part of the cable run. This is absolutely good planning.

Could both runs be bad? He tried both and got the same results. Yes, this is a possibility, but I doubt it. Too easy.

Could it be the length of the exposed center conductor? Yes, this is a possibility, but I also doubt this, too. The system was operational from the start and the installer has technical background to know about these things. Too easy and it doesn't match the symptoms (gradual degradation).

Since the owner/installer has background with cable systems, he knows to install a ground terminal block hear where the cable enters the home.
I suspect that the trouble lies between this point and the receiver. Most people, pros or amateurs, would route a solid cable run between the LNBF and the Receiver. Did you? I did not. I don't think that this man did so either.

I think that we need Stiche to check the signal at each of these junctions. Then we can discuss the situation better.

RADAR
 

AcWxRadar

SatelliteGuys Pro
Apr 26, 2006
4,575
4
40 miles NW of Omaha. Omaha?
Remember this rule for troubleshooting... Divide and Conquer! Break the system down into blocks and isolate the problem to one particular block, then break that block down and continue refining your search in this manner until you isolate the one component responsible for the error. Yes, it requires time, but so does growing old.

RADAR
 
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