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Troubleshooting your RV's TV Coax Cabling.



Perhaps the best way to check out the coax in your RV is to do a DC Continuity test. While this won't detect every problem, it will at least provide you with a basic Go-No Go indication, and will identify perhaps 90% of wiring problems. There is usually no need to use expensive and exotic Time Domain Reflectometers (TDR) to determine if the wiring is good or not. Simple tools will work... and in fact, even though I did this task in my RV, you can do the same thing in your home or residence.



The traditional method of checking coax is with an ohm meter and a shorting wire. You typically test for an open by shorting the wire between the center pin and shield at the distant end, then check for a short by removing the shorting wire at the distant end.

A product such as the Klein "Coax Explorer" makes this task easier, and if you buy the multi-coax tester, you can quickly check (and identify) several cables. However, for RV use, the single tester is sufficient. This is a really inexpensive device, and one should find it's way into your toolbox.

Hint, put the tester and load into a little box with a couple of spare f-conn barrel connectors.





Another almost indespensible item when you are troubleshooting is to use a f-conn wrench. While this won't help in determining the fault areas, it surely helps lower your frustration - which indirectly helps in your troubleshooting skills. This is an almost essential item. There are a couple of types of these wrenches; one having a scredriver type handle, and the other just a larger diameter disk that allows easier installatin and removal. I like the second type the best as you can get behind areas easier with it.


Dynamic/RF Testing


If DC continuity testing does not work, then a signal strength meter is an asset. This meter will give you the received signal strength coming from the antenna. Obvously the closer you are to the proximity of a TV broadcast antenna, the stronger signal you will receive. However, the signal strength is not as important as the change in signal along various points in your system. Of course, this assumes you have a moderate signal to begin with.

Essentially, you would start at the antenna's output, check the signal strength, then move on down the line - checking each cable connector from the antenna to TV. If you find an appreciable loss in signal from one point to the other - then the malady is likely what is causing the loss in signal - whether it be a coax cable, RF switch, or other device.




In the above graphic, the example shows a piece of coax that was crushed within the walls of a RV when it was constructed. It did not cut through the coax, and the coax shows good in the DC Continuity test. However, it has a severe problem and will not pass the full signal.

This can only be determined by a Dynamic/RF test, either by use of a signal strength meter, Time Domain Reflectometer, or similar device.

The signal strength meter will work in most cases, but if you really want a TDR, they cost between $500 and $5,000 for a good one.

Time Domain Reflectometers.


Believe it or not, the coax to the right was a "splice" made by a previous owner of a boat I used to own. While this example is a boat, the lesson learned is the same. The signal through this splice was marginal at best. The DC Continuity was OK with this splice, but the RF performance was lacking.

In that regard, the simple ohm meter or Klein Coax Explorer test would have not discovered this problem - but the signal strength meter test would have. I did not have a signal strength meter at the time, so I was even lucky to find this splice. This is the kind of thing that can really be frustrating if you don't have an easy means to troubleshoot the problem.

By the way, the only acceptable way to splice coax is with a barrel connector intended for that specific purpose.


Installation Practices

Incredible as it seems, a common reason for faulty coax is a poor installation - either at the factory or dealership. So if you are having problems with your TV system, do not discount installation problems.

Common installation problems include staples through the coax, excessive bend radius, or even crushing of the coax. If the coax is deformed in anyway, this could lead to problems. Cable manufacturers typically recommend that a coax cable should not be bent in a radius tighter than 5 times it's diameter. That means for a 3/8" diameter coax, a the bend should not be sharper than around 2" radius.

To put that into perspective, a DVD or CD disk is around 4" in Diameter, which of course has a 2" radius. So, no coax in your RV should have a bend sharper than the edge of a DVD. In fact, as haphazard as some installation practices are, you might even have a hard time finding a coax in your RV that meets this criteria.

Will a coax work that is bent sharper? Yes, most likely it will. However, sharp bends can introduce signal performance issues, especially at the higher frequencies (such as satellite TV). Since these effects are cumulative, a TV signal migrating thru several sections of bad coax is asking for trouble.


Testing Coax Video.


Using the King SL1000 Signal Strength Meter.


If you use a signal strength meter such as the King Controls SL1000, you can also permanently attach it to your RV's antenna coax system. This will allow you to fine tune the antenna's direction for the strongest signal.


Using the Klein VDV512-058 Coax Explorer .


Thie Klein Coax Explorer is useful if you have a bunch of coax wires going all over the place. It allows you to identify each coax cable easily. I had to do this on a RV as the actual wiring was nowhere near what the manual said it was (pretty much normal for the RV industry).