Troubleshooting Coax - Process of elimination the only way?

[StevenMark]

I have two 625 dual tuner receivers and one LNBF quad. Receiver “A” is in building 1 and Receiver “B” in building 2. The dish with quad LNBF is attached to building 2. Two cables run to each receiver. Everything was working fine until recently.

Here’s the problem: For the last couple of months, receiver “A” loses access to some channels about half the time. Receiver “B” works perfectly all the time. If I disconnect receiver “B”, the problem with receiver “A” goes away! It’s not enough to just power it down and unplug it; the dish cable must be removed from “B” to cure the problem with “A”

I tried these things:
Replaced the LNBF – no change.
Swapped the DP Quad for a DPP Twin + Separators – no change.
Traded places with the receivers – no change.

Moved receiver “A” to building 2 with receiver “B”. Ran a temporary coax to the DPP Twin. SUCCESS! Both receivers work perfectly.

I seem to have isolated the problem to a segment of coax. The segment is about 100 feet long and is in buried corrugated drain pipe. It’s not watertight. The cable is old ribbon cable from when I had a C-band dish.

Anyone ever seen this kind of cable problem before? Troubleshooting cable for continuity is easy but I don’t know how to test it for “dicey”, other than how I did it.

 

[waylew]

Time to run some new rg6,problem solved.Cable does go bad for various reasons.

 

[renegade734]

I'm not an electrician, although I play one on TV ... is it possible that a bad ground exists in building 1? Or maybe a hot and neutral switched?

 

[rglore]

Cable is most likely saturated internally with dirty water and shorting out the LNB power. Always eventually happens with non-flooded cables continuously exposed to water.

 

[navychop]

You found your problem. You know how to fix it. Just make sure it's high quality 3GHz swept cable - you don't want to be doing this again.

 

[dvrexpander]

What is the freq for the Cband cable? I'm going to assume 1450 or 2250. How long have you had the 625 running off it cause 1450 won't work and if you had 2250 its likely the added voltage thru the cable finally ate it up being that old and yes cable in the oddest sections can go bad.

As stated - replace it with some good quality RG6 3Ghz to solve issues and future proof....be sure to pull 3 new lines!

 

[MikeD-C05]

My mom and dad have a sat dish that was installed using RG6 to the outside of the house and then a barrel connector with looks like RG59 cable inside the house through the attic and down the wall to the living room tv. They have had the picture periodically cut in and out on sat and ota stations and this has been going on for a number of years. I had installed the newer dish on the pole on their roof when they went with the western arc 1000.2 sat dish and the terk 44 clip on antenna-since my Dad doesn't want more than one cable coming into his house.

I didn't change out the cable inside the house ,since DISH re-used it and DIRECTV re-used it first. All the switches , diplexer for the ota and sat, I have changed and all the coax to the 722k have been updated and changed . The receiver has been changed and upgraded over the years and it still has loss of video for a few seconds here and there regardless of the different receivers over the years. But I am thinking that the RG 59 that my mom installed herself ,back in the late 70's for cable tv, is what is causing her problems with picture cutting in and out. I told her we could buy some more RG6 cable from Radio shack and connect it to the barrel connector and then pull from the wall fish by the tv till the old cable is all pulled out and the new RG 6 is pulled through the attic and down the wall till it can take the place of the old RG 59 coax.

Do y'all think that replacing the RG59 would fix her picture cutting in and out since I have eliminated all other possibilities? I heard that coax can fail and I think that over 35 years old coax could of failed or starting to fail which could be causing the video cutting in and out. The sat dish is peaked well and I redid it last when we had Hurricane Ike in 08 and they get great strengths on all their signals. I re-checked this week so I know it isn't the dish not being peaked.

 

[KKlare]

While RG59 and RG6 are both "75-ohm" cables, they are different.

RG59 has solid polyethylene around a solid copper alloy core wire.
This increases the dielectric loss and the alloy increasing the strength but raises the DC resistance.
Cheap versions may use a copper plated steel wire, they are bad because
the steel has a higher resistance and is magnetic and thus a higher impedance.

RG6 has a spiral wrap of poly, lowering the dielectric loss, around a larger core wire which makes it also 75 ohm.
The core should be solid copper (stranded on some other types of cable).
The denser the shield, the better. Avoid a shield with a loose mesh. Silver plating is hard to find but better.
Double and triple shields improve the exclusion of outside signal and are lower-Z conductors.
Watch the quality of the terminating connectors.

Just my experience, -Ken

 

[sam_gordon]

Cable is most likely saturated internally with dirty water and shorting out the LNB power. Always eventually happens with non-flooded cables continuously exposed to water.

If that was the case, why does Receiver A work if Receiver B is disconnected from the dish?

 

[boba]

?

 

[hudgreen]

I'm not an electrician, although I play one on TV ... is it possible that a bad ground exists in building 1? Or maybe a hot and neutral switched?

Bingo!

Are building 1 and 2 on the same power meter?
At the very least I bet it has its own electrical sub panel and you are getting some sort of ground feedback through the coax.
Disconnect coax at #2 (be careful) and measure AC voltage between coax (shield) and receiver ground
I have seen voltages as high as 90 volts before when there should be almost none
Keep in mind that this voltage may only show up when,for instance, the refrigerator is running.

when you ran a bypass wire you (I assume) bypassed the ground point(s)

If this is the problem, the recommended fix is to call an electrician as your buildings may not properly grounded (bonded together)
A separate dish on each building would also (isolate) the two
there are other way to isolate the ground feedback but I wont recommend those fixes in this forum

 

[navychop]

....The core should be solid copper (stranded on some other types of cable).....

Isn't the solid copper just a bit better for current carrying to feed LNBs, but the copper coated steel just as good for signal quality?

 

[sam_gordon]

I assume sam Gordon is replying to another thread. Is the F-81 connector a white or a blue center? A simple test of the cable is to run a cable in through a window for a couple days and see if the drop outs continue.

Huh? I even quoted the post in this thread I was replying to. The quote function is a great feature. You might want to try and use it. There seem to be two issues in this thread alone, and I'm not sure which one YOU are replying to. The OP even said they ran a temporary cable to receiver A and it worked fine. Something tells me you're not talking about the OP though.

 

[StevenMark]

The saga continues. I have an update at the bottom of my responses:

I'm not an electrician, although I play one on TV ... is it possible that a bad ground exists in building 1? Or maybe a hot and neutral switched?

Renegade, Everything's kosher with the hot and neutral - tested them to be sure. I did some detective work and found some "interesting" things with my grounding. Both buildings are on the same power meter (OK). Power runs from the meter to a splitter box, and each has its own service panel (OK). Each service panel has its own ground rod and they are NOT bonded to each other (NOT OK). This is a no-no since there could be a difference in potential between the two grounds. I bought a roll of stranded #6 to address this.

What is the freq for the Cband cable? I'm going to assume 1450 or 2250. How long have you had the 625 running off it cause 1450 won't work and if you had 2250 its likely the added voltage thru the cable finally ate it up being that old and yes cable in the oddest sections can go bad.

As stated - replace it with some good quality RG6 3Ghz to solve issues and future proof....be sure to pull 3 new lines!

dvrexpander, I don't know the frequency rating of the cable. It's very old (maybe 20 years) and it's not stamped on it. I've been running the 625 receiver on that cable for about 6 years with no problems.

Bingo!

Are building 1 and 2 on the same power meter?
At the very least I bet it has its own electrical sub panel and you are getting some sort of ground feedback through the coax.
Disconnect coax at #2 (be careful) and measure AC voltage between coax (shield) and receiver ground
I have seen voltages as high as 90 volts before when there should be almost none
Keep in mind that this voltage may only show up when,for instance, the refrigerator is running.

when you ran a bypass wire you (I assume) bypassed the ground point(s)

If this is the problem, the recommended fix is to call an electrician as your buildings may not properly grounded (bonded together)
A separate dish on each building would also (isolate) the two
there are other way to isolate the ground feedback but I wont recommend those fixes in this forum

hudgreen, yes they are on the same meter and separate panels as described above to Renegade. The 2 buildings' grounds are NOT bonded together I can fix that. The ground for the dish is a separate ground, not bonded to the building ground. I can fix that too. I am curious to see what the coax voltage is at building 2 - I'll check that and report back. But, since the problem happens even when receiver B is unplugged from electric, I don't see how non-bonded grounds could have an effect. Something I didn't think to check, though, was to see if unplugging the TV audio & video cables from the receiver would have any effect; it was still plugged into electric and attached to the receiver while having the problem. I've had these receivers sharing one LNB for about 6 years so something has changed. Yesterday I ran a separate coax to receiver 1 (to bypass the old buried coax) and this did not fix the problem. It's worth noting it was an old piece of "satellite foam rg6", about 100 feet long, that I had coiled up in by shop for about 15 years.


The grounding errors are a safety concern and I'll be fixing those. For whatever reason the 2 receivers no longer like being connected to the same LNB, so I made the problem go away by mounting a second dish at building 1. Problem solved!

 

[hudgreen]

The saga continues. I have an update at the bottom of my responses:





The grounding errors are a safety concern and I'll be fixing those. For whatever reason the 2 receivers no longer like being connected to the same LNB, so I made the problem go away by mounting a second dish at building 1. Problem solved!

Those are two words we like to see here on satellite guys.....problem solved!
Glad we could help