Finding Cable TV coax routing

[frankdamp]

We tried to use CG cable TV a couple of times on our recent trip and got absolutely horrible reception. These were the first attempts to use it since we bought this RV.

Back at home, I did some trouble shooting using a VCR as an input device. Got a good picture with the VCR signal going into the distribution box on both TV sets, whether going into the "cable", "aux" or "antenna" input sockets.

With the VCR sig going into the cable input in the power bay, the horrible picture/sound was repeated on all distribution box circuits. Ergo, there's a problem with the coax between the power bay and the cabinets above the windshield where the distbution box is located.

I have two options, I think. One is to put completely new "Cable" wiring in from the forward-most cargo bay on the LH side up inside the windsheil post trim and into the overhead cabinets. The other is to track down the existing coax to try and find the problem.

Has anyone tried gerting one of those utility finder companies to trace wiring in an RV or is there some gadget out there that will let me inject a singal into the coax and then go through the living area with a receiver to track where the wiring goes?

Option 1 looks like the simplest at this point.

Note that we're not over-the-air TV fanatics (we still have 4:3 CRT sets at home, no HD, no DVR, Comcast basic cable) but it can be handy to get local weather forecasts on the TV when were on the road.

Comments?

BTW, I ran a search, but didn't find anything.

[UFO Pilot]

You could try something like this: Cable Wire Coax Telephone Toner Tracer Tracker

I know it works on telephone wires.

[RickO]

I would think that you should be able to trace the wire yourself just by following it from the outside connection but if that doesn't look possible, I would probably agree with you that option one sounds pretty good.

Rick

[Alan_Hepburn]

Quote:

Originally Posted by wthomas1 You could try something like this: Cable Wire Coax Telephone Toner Tracer Tracker I know it works on telephone wires.

That unit looks like you are supposed to pierce the wire to determine continuity. That works well with telephone wires but not with cable. When you pierce the cable you'll short the shield to the conductor, rendering the test useless. I would suspect that the cable is in behind the wall, floor, and/or ceiling panels, held in place with wire ties and/or staples. Often the lackey running the stapler ends up putting a staple or two through the cable, causing problems such as the OP is reporting. The best solution is to run a fresh cable and try to hide it as much as possible.

[traveldawg]

You have a few options.....
1. Purchase a coax cable checker such as this.... COAX TESTER
> With this you can confirm exactly which cable inside the coach goes to the input at the outside of your coax.
> You will want to disconnect cables one by one inside (at your switch box) one by one to determine which cable goes from the outside port to inside.

2. Run the output of your VCR into the outside coax input and plug the the most likely end of that cable inside your coach directly into a TV.
> Most likely you will at least confirm which cable comes from the outside; and you are likely to find whether you have a good signal or not.

Assuming you can find the right cable from outside your coach running it directly to your TV you can eliminate problems like bad switch boxes, faulty switches/antenna amps, bad patch cables, etc.

My guess (very educated guess - I do this stuff daily) is your coax is fine. You problem is either in your switch box or the antenna amp device (assuming you have one of those).

Good luck.

[frankdamp]

Traveldawg:

I have actually done what you suggested. With the VCR signal going into any of the inputs (AUX, ANT, VCR, Cable) in the distribution box in the front overhead, I get excellent pictures on both the front and bedroom TVs. With the VCR connected to the cable input in the power bay down the back, the picture and sound are very poor. Switching the "Cable" coax to the other channels doesn't help. With the VCR in the cable circuit, there are no signals on the ANT, AUX or VCR cables at the distribution box, so I'm sure I've got the right one. The only thing I haven't tracked down is whether there's an in-line splice connector somewhere up front that may be giving a high impedance or a corrosion short between shield and conductor.

I think a new cable run would be easier than trying to find where there might be a problem, as I'm not sure I could pull a new cable through by attaching to the present one. I may try pulling a high-strength line through from the power bay with the existing cable, then pull a new coax through with the line.

A new run would go from the baggage bay just aft of the driver's side front wheel into the cabin just forward of the living room slide, then up behind the dash and into the windshield trim, into the driver's side overhead cabinet and across to the passenger's side where the distribution box is.

[traveldawg]

Quote:

Originally Posted by frankdamp Traveldawg: I have actually done what you suggested. With the VCR signal going into any of the inputs (AUX, ANT, VCR, Cable) in the distribution box in the front overhead, I get excellent pictures on both the front and bedroom TVs. With the VCR connected to the cable input in the power bay down the back, the picture and sound are very poor. Switching the "Cable" coax to the other channels doesn't help. With the VCR in the cable circuit, there are no signals on the ANT, AUX or VCR cables at the distribution box, so I'm sure I've got the right one. The only thing I haven't tracked down is whether there's an in-line splice connector somewhere up front that may be giving a high impedance or a corrosion short between shield and conductor. I think a new cable run would be easier than trying to find where there might be a problem, as I'm not sure I could pull a new cable through by attaching to the present one. I may try pulling a high-strength line through from the power bay with the existing cable, then pull a new coax through with the line. A new run would go from the baggage bay just aft of the driver's side front wheel into the cabin just forward of the living room slide, then up behind the dash and into the windshield trim, into the driver's side overhead cabinet and across to the passenger's side where the distribution box is.

Frank,
See if your cable run from the outside to the inside runs through one of those antenna/cable/amplifier devices (the one that is the size of a wall plate and usually has a 12V DC outlet, coax connector and switch for the antenna amplifier. If it does route through there try bypassing it.

I find this kind of wiring situation quite bothersome and in almost all cases it degrades the coax signal. I usually end up putting in a small A/B switch (Walmart; about $5) to select cable without going through that amp or antenna with the antenna signal going through that amp.

Like you said: if all else fails, run it directly from the bay to inside as you described.

Good luck.

[HD4Mark]

The phone toner will work fine by just connecting one alligator clip to the shield and the other the core wire at one end. You can't hear it through much of a wall though. The coax tester is a nice piece of test equipment but way more than you need.

To test for a short get a $5 VOM from Harbor Freight or somewhere. Remove any equipment from the ends and test between the shield and wire for a short with the VOM set to ohms. Touch the test leads together to see what a short looks like on the meter if you have never used one. If you want to see what coax you have you can wire together the shield and wire then start looking at the other ends for the shorted one.

I find most of the time the connector is the culprit on these so I give them all a tug to see if one comes apart.

Good luck these things can be frustrating.

[noeldale]

The phone toner works great. I've used it to wire total manufacturiing plants before wireless systems were being used. Just be sure to have any power amplifiers turned off.

[Tincup]

I've been a ham radio operator for 45 years and have never seen a coax cable go bad. Now having said that, I have seen signal degradation caused by moisture entering the cable, puncturing the cable accidentally, etc. There has always be an outside influences of some kind to cause the loss of signal. In an RV the cable is not exposed to the elements, except a couple of feet at each end. If you have always had a problem with this cable it's possible it was pinched during manufacture of the RV, if it just started to go south, I would check the connectors at each end first, even if they look good I'd replace them, much easier and cheaper, than running new cable.

Good luck in your search for the culprit.

[frankdamp]

As far as I can determine, the "cable" wiring is just a simple coax run from the power bay just forward of the rear wheels to the front overhead cabinet on the passenger's side. I don't believe there are any amplifiers in that run.

The distribution box is a non-powered switching device that routes various inputs to the VCR for recording, to the front TV and to the bedroom TV.

Since we haven't gone for an over-the-air converter (yet?), I haven't even tried the Winegard antenna, so its amplifier isn't in the loop I'm having problems with.

I will check for any indication of a short or high-resistance path between the conductor and the shield, but if I detect one, there's no way of figuring out where it is. The wall plate in the power bay looked a bit dodgy, so I replaced it, without any improvement.

FYI, I've been in the airplane electronics and flight simulator business during my 28 years at Boeing, so I do know my way around these things. The more I investigate, the more sure I become that there's some damage to the coax somewhere and the chances of finding it are infinitesimal. A new installation seems the most sensible solution. It'll make a nice off-season project!

[UFO Pilot]

When I was having TV reception problems (still under warranty) one of the things the shop did was to run a cable from the source directly to the TV, bypassing the factory coax completely. After verifying they had good reception, they moved the coax from the TV to the Winegard distribution box. They isolated my problem to the Winegard problem.

[HD4Mark]

Quote:

Originally Posted by frankdamp FYI, I've been in the airplane electronics and flight simulator business during my 28 years at Boeing, so I do know my way around these things.

Frank,
Hope I didn't sound like I was talking down to anyone. I was in telecommunications for 32 years and met my wife at work. She always told me I explain things like the other person already knows it but in this case it is obvious you do.

Mark

[frankdamp]

No problem, Mark. I guess I hadn't fully explained at the start that I had run several tests and had narrowed the problem down quite a bit.

I do plan to find a used over-the-air converter box during the off season so we can also use the antenna.

We aren't TV "junkies" - it was our fourth trip after buying the rig before we tried to use the cable hook-up. At home, because we live in an RF "black hole", we have no option except cable or Dish. DW insists on being able to get CBUT-Vancouver, which none of the satellite outfits carry, so we're on Comcast cable. Both home TVs are 4:3 CRT analog types, as are those in the RV, but with Comcast's own digitization, we finished up with their set-top boxes.

Even though there's quite a weight saving, I don't see going to 16:9 LCD in the motorhome before the stick house, so there will be a converter in our future!