Coax testing - How should I test the connection

[jonwestuk]

Hi,

I have finished installing all of my cabling in the house which includes a number of runs of coax cable. Before I close all my walls I want to ensure that both the wire and terminations are properly functioning so as to be sure that everything will work when it is plugged in. For my Cat6 I used a network tester which proved really useful, but I cannot find anything similar for Coax.

What do you all use? I guess I could use a multimeter to check for shorts, and if I were to then short the wire at one end and do a continuity test on the other, however that seems like a bit of a pain in the rear! Do any of you have any good tricks or cheap tools for this?

Thx,

Jon

 

[DetlefSchmitz]

I'd put a resistor across one end, and measure it from the other end.

 

[3DGuy]

I picked up one of these for our 6 Coax cable runs for our full house re-wire. I ran the Cat 5e's and the Coax runs then we used this to test each end. Beeps if there is a loop. Nice and simple.

http://www.ebay.co.uk/itm/Pocket-si...?pt=UK_Sound_Vision_Other&hash=item25776ee946

 

[winston1]

I'd put a resistor across one end, and measure it from the other end.

That will test for continuity or short circuits at DC but is pretty useless for its performance at UHF or satellite IF. Sharp bends or kinks can have drastic effects. Put an aerial or sat dish on one and and a TV or sat box on the other end to test in the absence of test gear.

 

[jonwestuk]

I'd put a resistor across one end, and measure it from the other end.

That will test for continuity or short circuits at DC but is pretty useless for its performance at UHF or satellite IF. Sharp bends or kinks can have drastic effects. Put an aerial or sat dish on one and and a TV or sat box on the other end to test in the absence of test gear.

the only TVs I have are 42 inches and above. with 9 coax runs I dont fancy moving it around that much

 

[jonwestuk]

I picked up one of these for our 6 Coax cable runs for our full house re-wire. I ran the Cat 5e's and the Coax runs then we used this to test each end. Beeps if there is a loop. Nice and simple.

http://www.ebay.co.uk/itm/Pocket-si...ound_Vision_Other&hash=item25776ee946[/QUOTE]

That will do. Thanks for your help.

 

[AlanE]

Hi,

I have finished installing all of my cabling in the house which includes a number of runs of coax cable. Before I close all my walls I want to ensure that both the wire and terminations are properly functioning so as to be sure that everything will work when it is plugged in. For my Cat6 I used a network tester which proved really useful, but I cannot find anything similar for Coax.

What do you all use? I guess I could use a multimeter to check for shorts, and if I were to then short the wire at one end and do a continuity test on the other, however that seems like a bit of a pain in the rear! Do any of you have any good tricks or cheap tools for this?

Thx,

Jon

A lot of network testers have facility to test coax cable also. You might have to obtain a coax socket to BNC adapter but they are easy to find.

Another alternative is to wire a network plug to a coax plug or socket. Use same network pair at each end and your current network tester should work a treat.

 

[winston1]

I picked up one of these for our 6 Coax cable runs for our full house re-wire. I ran the Cat 5e's and the Coax runs then we used this to test each end. Beeps if there is a loop. Nice and simple.

http://www.ebay.co.uk/itm/Pocket-si...ound_Vision_Other&hash=item25776ee946[/QUOTE]

That will do. Thanks for your help.

No it won't. That will only test the continuity which as I said previously will have no relation to its performance at RF.

 

[AlanE]

My suggestion above will also only test continuity, not performance.

 

[DetlefSchmitz]

I guess winston1 is suggesting you buy a TDR meter.

I would say that you either use a resistor and multimeter (£10) and you probably already have the meter so resistor and coax plug (50p). This will also give you more information than the ebay jobbie - however cool it may seem to have one.

Or you buy a reflectometer (several hundred quid).

It depends how much risk you place on whether you damaged the coax by bending it sharply.

 

[Greenie9657]

Hi

Ive worked with co-ax for years on aircraft and in the home and there are 2 tests I use to check out a new length of co-ax.

1st one is to just connect the dam thing up and see if it works.

2nd one is I use a multi-meter and con check the centre pin to the outer socket/connector. Make sure both ends are disconnected though otherwise the aerial will through up a short. Do centre pin to outer shell on both ends then to make sure I do centre pin to other end outer shell and vise-versa.

Other people may have different methods but this has never failed me if Ive only had a multi-meter to hand. Just 1 strand of outer coax on the centre pin will through up continuity and will cause interference if it works at all. Give the ends a wiggle while checking them just to check integrity.

Hope this helps

 

[DaftPunk]

I picked up one of these for our 6 Coax cable runs for our full house re-wire. I ran the Cat 5e's and the Coax runs then we used this to test each end. Beeps if there is a loop. Nice and simple.

http://www.ebay.co.uk/itm/Pocket-si...ound_Vision_Other&hash=item25776ee946[/QUOTE]

That will do. Thanks for your help.

No it won't. That will only test the continuity which as I said previously will have no relation to its performance at RF.

It's a telly aerial ffs hardly rocket science. It'll either work or it won't.

 

[Greenie9657]

I picked up one of these for our 6 Coax cable runs for our full house re-wire. I ran the Cat 5e's and the Coax runs then we used this to test each end. Beeps if there is a loop. Nice and simple.

http://www.ebay.co.uk/itm/Pocket-si...ound_Vision_Other&hash=item25776ee946[/QUOTE]

That will do. Thanks for your help.

No it won't. That will only test the continuity which as I said previously will have no relation to its performance at RF.

Exactly what he said!!!

It's a telly aerial ffs hardly rocket science. It'll either work or it won't.

 

[plugwash]

It's a telly aerial ffs hardly rocket science. It'll either work or it won't.

I wish.

With modern compressed, error corrected digital transmissions what tends to happen when the signal is marginal is it works most of the time but from time to time the signal breaks up in a REALLY annoying manner (most of the annoyance comes from the time it takes to resync, analog TV suffered from interference spikes too but it recovered much quicker) as the bit error rate crosses from "correctable" to "uncorrectable".

 

[STEVEROG]

Gents,

The standard measurements (if you have the kit to do them) are to measure the insertion loss of the coaxial cable, and the return loss (or VSWR). The former measurement tells you what the dB loss is of your run of cable. You can then compare this to the specification of the cable. Note that your cable loss may be exactly as per the specification but if you've designed in coax that has too much loss you're in trouble even though the installation is ok.
Next, the return loss or VSWR measurement tells you how much of the signal from the antenna will flow into the coax and how much gets reflected. Ideally you want none of the signal reflected. If the coax is kinked, damaged, has moisture ingress etc you may have problems. The bigger issue however is generally the connections which for non professional kit can be really dire and cause quite bad points of mismatch. That's how things should be done but unfortunately the kit to do these measurements isnt cheap. Ideally a vector network analyser. Alternatively if you have good electronics knowledge you could build a return loss bridge and other useful RF engineering items and do your own tests.

The much more simple alternative is to install your equipment and then have a look at the signal levels during set up. If you can do a comparison of power levels with the kit connected directly to the antenna versus with the kit on the end of your installed coax you can then add in a section of the same length of coax and see if the signal levels are about the same. If the levels are significantly different then you know you've damaged the coax....easy.