Flaky RG-59 cable?

be236 · #1 (**permalink**) 12-04-2006, 03:57 PM

Hi,

I've got this 50 ft RG-59 cable I use between the LNB and my Fortec Classic box (yes, I know I should use RG-6)...

Anyways, it sometimes works to bring in a signal and other times not... when I was watch TV, it would be fine, then intermittent say "bad signal" and back to getting a signal (nice strong 60% quality) again, and back to "bad signal" etc... I made sure my connections on both ends are tight....

The cable is routed under my crawl space... Could the only explanation be that there is a "kink" somewhere along the cable run? I guess the way to detect this is to get out my ohmmeter and measure continuity on the outer metal contact and inner wire on my ends and look for a low ohm value, say 1-2 ohms...

Or does the cable have to be really straight? Who knows how curvy the cable is underneath the crawl space yet...

heheh..

rainman · #2 (**permalink**) 12-04-2006, 04:37 PM

Quote:

Originally Posted by be236

Hi,

I've got this 50 ft RG-59 cable I use between the LNB and my Fortec Classic box (yes, I know I should use RG-6)...

Anyways, it sometimes works to bring in a signal and other times not... when I was watch TV, it would be fine, then intermittent say "bad signal" and back to getting a signal (nice strong 60% quality) again, and back to "bad signal" etc... I made sure my connections on both ends are tight....

The cable is routed under my crawl space... Could the only explanation be that there is a "kink" somewhere along the cable run? I guess the way to detect this is to get out my ohmmeter and measure continuity on the outer metal contact and inner wire on my ends and look for a low ohm value, say 1-2 ohms...

Or does the cable have to be really straight? Who knows how curvy the cable is underneath the crawl space yet...

heheh..

it shouldn't matter if the cable is straight or not just as long as it's not shorted together or open circuit.

be236 · #3 (**permalink**) 12-04-2006, 04:42 PM

But the question is .. how do cables "go bad?" ehheh... I guess maybe it got twisted hard and that broke some connection at that point in the cable....

Again, I guess I'll have to get out my ohmmeter to measure connectivity on both ends...hehe... saves me from buy a $20 RG-6 cable.

bobkat · #4 (**permalink**) 12-04-2006, 05:59 PM

Its likely the connectors - like rainman says, short of an open or shorted cable there's not much that can go wrong with it. Kinks should not present a problem but some engineers suggest an 8" minimum bend radius for RG6 when used with KU signals. I've never encountered a defective cable on any of my service calls - bad connectors, oh yeah...

kat

lostinthewoods · #5 (**permalink**) 12-04-2006, 07:25 PM

Another thought might be "rodents", I have had occasion in such spaces to find they like to eat plastic!

Look for chewed spots.

Lost

be236 · #6 (**permalink**) 12-04-2006, 07:31 PM

Well, I bought a cable-connector kit that allows me to cut RG6/RG59 cables, stripper to pull the ends out and put in new F-connectors.. I guess I could just cut the ends and make new end connectors.

I have noticed on another RG-59 cable, that I dont get connectivity (using ohmmeter, I expect 1-2 ohms maybe) so I get no signal when connecting to LNB to receiver.. yet, when I use this cable to connect between the receiver and TV into its F-plug, it shows the picture just fine...

I guess TV signal is less stringent than between LNB to receiver... hmmm.. oh well...

As for rats in my crawlspace, I thought about that too, but unlikely, considering I have other cables under there and dont have any problems with them over the years. hehehh...

That is weird how the end connectors could be loose as not to make a connection... oh well....

rainman · #7 (**permalink**) 12-04-2006, 08:22 PM

check and see that your coax has'nt got any weather cracks if so it could allow water intrusion causing it to short out intermittenly.

bobkat · #8 (**permalink**) 12-04-2006, 09:20 PM

Quote:

Originally Posted by lostinthewoods

Another thought might be "rodents", I have had occasion in such spaces to find they like to eat plastic!

Oh yeah, I forgot about the rodents. I have replaced lots of coax due to raccoons chewing it all up for some reason - guess its tasty...

kat

wejones · #9 (**permalink**) 12-05-2006, 10:17 AM

Lots of interesting sub topics here. :-)

First, I have heard RF experts on both sides of the issue of whether a kinked or coiled coax will reduce signal level. In general it won't make any difference, but you should try to keep it straight, if for no other reason, to make sure that you don't compress the dielectric between center conductor and shield. However, I don't think a kinked coax would cause intermittant reception as is seen here.

Re the "rodent" thing. Boy can I verify this. Not only will they eat the plastic insulation, but they actually chew up wires. I leave my boat outside in the winter, and the mice and chipmunks have chewed completely through several wires in the electrical system. However, again, while this could cause a go/no-go situation, I don't see it being intermittant.

Bad connections are also a common problem, but unless there is something there moving the wires at the connection, I again don't see this being intermittant, except out at the dish, where wind might be moving the dish enough to wiggle the wires.

I also don't think that RG-59 vs RG-6 is an issue here, as I'm using about 75' of RG-59 on one of my LNBs and it isn't a big problem, except at the upper end of the IF band perhaps.

My suggestion is that this is probably either a reception problem or an LNBF stability problem. Ie reception wise, perhaps the bolts are a bit loose on the dish or perhaps the pole isn't rigid, and perhaps wind, or a bird sitting on the lnbf, moves the dish just enough to temporarily kill your signal. Or, if your alignment is a bit off, and you are actually picking up two different signals from different sats or polarity, and the receiver occasionally locks onto the weaker signal for some reason.
I have also noticed intermittant lock in the past, on two of my receivers, when the freq/SR parameters are off a bit off. I know one time, there was one signal which was posted on another forum as having a 20,000 SR value, and MANY people, including me, were having problems with it popping in an out of lock as seen here. I used the SW method to determine the SR value, and found that it was actually about 20,010, instead of 20,000, and when the SR value was corrected, it stopped popping in and out of lock. This is strange to me now, because I have seen many examples of being able to lock signals which are WAY off freq on the SR value, and still lock fine, however I think that this depends on the receiver. Different receivers also have different capabilities with respect to being able to tune a signal that is off frequency. This is particularly important on narrow (low SR) signals, because many of these cheap LNBFs can drift several MHz, and if the receiver isn't capable of following the drift, you might see the signal go in and out of lock when the LNBF drifts. I know that the LNBF I bought from Sadoun is 2 MHz low on the average, and drifts up to another MHz or 2 around that, so I sometimes have problems with narrow signals locking. On my FTA receiver, I just set my LO freq to 10752 to compensate, but on my DCII receiver I can't do that, so that LNBF sometimes makes it difficult for me to lock narrow DCII signals.
Anyway, just a couple other possibilities. You might try to change the FREQ/SR values a couple MHz higher or lower when you're having this problem, just to see if it helps.

be236 · #10 (**permalink**) 12-06-2006, 01:00 AM

I still think it's a cable issue... I will know more for sure when I measure connectivity on both ends using an ohmmeter...

Also, I have seen store sell RG6 vs RG59 F-connectors... Can I use an RG6 connector with an RG59 cable and vice versa? The size difference seems so small...

wejones · #11 (**permalink**) 12-06-2006, 08:40 AM

Quote:

Originally Posted by be236

I still think it's a cable issue... I will know more for sure when I measure connectivity on both ends using an ohmmeter...

Also, I have seen store sell RG6 vs RG59 F-connectors... Can I use an RG6 connector with an RG59 cable and vice versa? The size difference seems so small...

There seem to be many different versions of both RG59 and RG6, and I always seem to have problems with the connectors not being quite the right size. Recently, I've been using a spool of RG6 that I got at Sadoun with the RG6 connectors available at RS. They don't crimp down watertight, but they make a pretty secure connection if you slip the inner tube of the connector between the shield and the insulation. I usually leave just about 1/8" of the shield/dielectric exposed, and slip the connector on so that the exposed shield just slightly pops through the hole inside the threaded nut, then I crimp it down. This doesn't seem to be the recommended way, but it works well for me, and is very quick. I'm not sure if it helps, but I've also been smearing a bit of that tar like coax seal stuff over the insulation before slipping on the connector, in hopes that it might help keep water out. I also use this on outside connections, but I'm trying to come up with an alternative way of sealing the outside connectors that might be easier to get apart in cold weather.
If you don't get the connectors that match the cable, then the inside tube isn't the right size to do what I described, and I've had to do strange things to attach the connections, like peal back the shield over the insulation, and other similar things, which make the connection ugly. I've also found that the fairly heavy duty crimping tool available at RS isn't quite the right size, and it helps if you wrap a few layers of aluminum foil around the fitting before crimping, which makes it crimp it a bit tighter.
I've been making coax connections of all kinds for decades, and have multiple tools for making it easier, and I've NEVER made a good looking connection, which is embarrassing.

bobkat · #12 (**permalink**) 12-07-2006, 03:01 PM

Actually, rainman brought up a good point in one of the above posts but I'm too lazy to go look for it to 'quote' it; but he said watch for a small cut in the cable jacket that would allow water to enter and possibly short out the center conductor to ground -- I've had this happen and it drives you nuts trying to troubleshoot it, because it usually is intermittent.

kat

rainman · #13 (**permalink**) 12-07-2006, 03:03 PM

yeah had this problem with my old c band cable kat a few years back so i just replaced it all.

pictureon · #14 (**permalink**) 12-09-2006, 12:24 AM

Why don't you change the cable. It's the best way to find out. Why spending money on tools and take too much time to test this and that? Just buy the RG6 cable and change the RG59 . It would cost less.

glen4cindy · #15 (**permalink**) 12-15-2006, 07:38 PM

Quote:

Originally Posted by wejones

I've been making coax connections of all kinds for decades, and have multiple tools for making it easier, and I've NEVER made a good looking connection, which is embarrassing.

The best connectors I've found is what I used to use at the CATV co. where I worked. We used quad shield RG-6 and Snap-N-Seal connectors with a little blue ring. The blue ring had an o-ring that sealed everything up at the connector end and it always came out looking clean and neat.