Can anyone direct me to an inexpensive coax/video tester. I'm looking to cut into an existing coax in an attic with a splitter and don't know which end will be the feed. Hate to carry a TV up there with me.

TIA,

Joe

can you ring it out with a ohm meter?

If possible open up the coax at a connector before the attic & clip the shield and center connector together. Once you are in the attic, you can find determine which end of the cut cable of shorted with a ohm meter.

Home Depot sells a relatively inexpensive tone/trace unit for about $50.00 that is made by Ideal. It's not very sophisticated, but is generally intended for just the kind of simple stuff you are looking to do.

A 1.5V penlite cell and an LED would do the same thing.

As a cable technician, I recommend/request the following: DO NOT PUT THE SPLITTER IN THE ATTIC!!!!!!!!!! Run the new line back to the existing splitter, and either use an unused port on that splitter, or add another splitter to the existing one.

With my dad being a cable guy, I gotta agree. Run it to the source, don't tap off.

Ian A.

these are like 15.00

I did an analysis of the CATV system in my home when I first got HDTV, and was astonished to discover I was splitting my signal down to about 2% of the original signal at the box. All the splits really add up...

5-way splitter at the drop- 4 ea to 4 TVs in the old house, 5th to another 4-way splitter in the addition. And then that goes to a 2-way splitter to feed the DVR and TV inputs. The DVR then has an internal 2-way splitter for the dual tuners.

20% x 25% x 50% x 50% = 1.25% per tuner in the DVR, both of which had crappy signals and a horrible picture that would constantly break up on several channels and never work at all on a few others. What it DID have, though, was an excellent signal meter! I added a 15dB amp, which increased signal strength, but didn't solve the problem, which was never signal strength (despite the losses), but signal-to-noise ratio- and the noise remained. I troubleshot all the connections and other lines, but the difference was negligible. (Even when disconnected from cable, I was getting a clear picture of several channels on my one TV- there was just that much EMI bouncing around.) The additional grounding point the amp offered is what finally fixed my TV- Grounded the amp, and BAM, every analog TV in the house cleared up considerably, and errors dropped to 0 at the DVR. Problem solved! My analog TV pictures are still quite lousy, though. I blame my neighbors, gotta be their fault, probably using a coat hanger instead of RG6 or something.

So... ah... don't mind the haters, just use a splitter in the attic

So what is it and where do I get one?

Sorry, I'll try and do that next time, job's already drywalled and can't fish down now.

http://www.hollandelectronics.com/newproducts.html

http://cgi.ebay.com/POCKET-TONER-RI...803QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Wow! A little off topic but I just saw this in that last link. About time they came out with something like this. http://www.hollandelectronics.com/catalog/catalog.php?product_id=Dark-Meter-System

I would recommend it to all of you guys who install coax. No need to wait for the cable or sat company to provide service and uncover your mistakes. Check each cable run or an entire system and know that your work is good before the house is sold.

-Hal

I know most people reading the thread are probably aware of this, but just in case anyone isn't.....

When it comes to clipping center and shield together to trace a cable with an ohmmeter or other simple continuity tester, remember that cables which run to an antenna may show a DC short under normal conditions anyway. A folded dipole on a regular Yagi array, for example, will do so. It might look like a dead short to DC, but it isn't at RF!

And a little off-topic I know, but when it comes to simple DC continuity tests, I wonder how many other U.K. readers still have one of the old dark green Hosiden Besson "Bleeptest" units, as were standard GPO issue for many years?

On that note keep in mind that most splitter ports are a dead short to DC. Also a staple through a cable is going to be a short also.

The OP asked about an easy way to identify the feed when cutting a cable to insert a splitter. Many times it is difficult to determine where the other end of a cable is so it is not always possible to disconnect the far end to put a tester on it or even know what it is connected to. The only way to handle this is to look for the end with signal on it then you know it's the feed. Only way to do that is with a signal level meter or a TV. There is no cheap tester that will tell you if you have signal.

-Hal

You could take a small portable TV with you, and touch the antenna to the center conductor. The active one should provide a nice strong signal on any VHF channel when you contact it.

I'm sad my little 1.5" LCD TV will be worthless come next year when all broadcast goes HD On the bright side, HDTV is awesome...

Instead of putting a dead short on the cable, one could use a resistor. Then you could identify between an open cable, a shorted cable, or a cable that has the correct resistance on it and is therefore intact and the one you want.

You could use a 75-ohm terminating resistor for this. It's already packaged in an F connector, so you could just use an F81 splice barrel and connect it straight to the cable you want to test.

In a lot of cable systems, you don't really even need a TV. Just use an FM radio (not a digital one, just a cheap analog tuning model with an antenna). Even if the cable system isn't rebroadcasting any FM stations (most aren't anymore), there are several cable TV channels with their audio in the FM band:

95 has it's audio at 95.75MHz
96 has it's audio at 101.75MHz
97 has it's audio at 107.75MHz

You could also use a radio scanner. I've used a scanner to identify cable signal leaks...just tune it to an audio carrier in the range that the radio can tune and then bring it's antenna near your cables. Should you start hearing the TV audio, you have a signal leak.

Here is a list of all the cable channel frequencies. Note that you must add 4.5MHz to the visual carrier to get the audio carrier:

http://www.jneuhaus.com/fccindex/cablech.html

Another way to check for signal, the cheapest way I can think of:

Since the video carriers are AM one could build a simple crystal-set style detector circuit in conjunction with a high-impedance amplifier or earphone. I expect this will emit a strong 60Hz tone (the vertical sync) when connected to an active cable line. This can be done with nothing more than a diode.

Several years ago when I used a cassette-tape adapter to feed my car stereo the input from my mp3 player, it did a fine job of picking up the video carrier's vertical sync and blasting the 60Hz tone through my car stereo speakers anytime I drove by a TV transmitter tower.

So I believe a simple detector circuit will work just fine for the purposes of checking for signal on a cable TV line.

Instead of putting a dead short on the cable, one could use a resistor.

At one time a long time ago we used to use a 9 volt battery and a DC voltmeter. Then we got smart and used a toner and probe.

As to your other methods to look for signal, remember that analog is either gone or soon will be gone on most cable systems. The actual channels are in groups within several digital carriers.

-Hal

That's true, but the data carriers make a distinctive sound when tuned with an AM tuner, so you could still use a scanner that is capable of picking up AM to check for signal. (Many scanners can, because the aircraft band is AM).

Why do you want to do things the right way, an electricans first pirority is figure how cheap and fast it can be done!

A splitter in the attic is not such a big deal to me as long as it's close enough to the hatch that I can get to it without going into the attic (or there are pull-down attic stairs and a floor).

Why do you want to do things the right way, an electricans first pirority is figure how cheap and fast it can be done!

I certainly hope you are trying to be funny.

-Hal

There are often many ways to do it "right." The best solution is always going to be a compromise between cost, practicality and efficiency. Safety should never be compromised. (At least, up to a point... I mean, we don't need #10 on 15A AFCI/GFCI breakers, dedicated to each receptacle in a house. Which, I guess, means we do compromise safety?)

Besides, cheaper install means less to mark up! Twice the cost=twice the profit! What kind of electrician are you, trying to save the customer money??

I'm hoping the same thing.

Ian A.

I sometimes use my little Darkstar D230 CATV tester for that type of situation. It can only determine if it is connected to an active CATV line, 50 Ohm terminated, shorted, or open line. It doesn’t offer any actual signal quality [SAM] measurements. Unfortunately, I just did a Google search and found that it is no longer in production. Maybe you can still find a good used one on ebay. I think it was only around $69.00 new, about six years ago.

Another unit I have that I know is still available, but is not as simple and straightforward to use, is the Progressive Electronics/Tempo CATV 402K tone test set. It looks like an ordinary toner/tracer, but can send signal through splitters, terminators, ground blocks, traps, etc, and can be direct coupled to an f-fitting. You can see if the line is open, shorted, or live by looking at the color change of the LED indicator. This kit is kind of expensive at about $175.00, but you can get double duty out of it by also using it for your regular toning and tracing.

For years, I’ve seen those little L-shaped Go-No-Go testers that another poster mentioned, but never managed to get around to trying one. That could be the most inexpensive solution. I think Specialized Products carries something similar.

I probably shouldn’t even mention this, but just in case some old Cable Dog tells you about it on the down low, I wouldn’t recommend using the idiotic and infamous “Taste Test”, that a few bone heads I used to work with a long time showed me. I can only describe it as like sticking a 9V battery in your mouth. Not to bright of an idea. If there is a problem with the neutral or grounding at the building, or a voltage spike somewhere in the system, it may be the last thing you ever taste.

It’s been quite a while since I’ve done it, but now that I’m thinking about it, I believe the second method I mentioned concerning use of the 402K kit, only works if there is a cable box connected and powered up for the line being tested. As I recall, the 402K indicated the active line from the DC voltage of the cable box output.

Don't you guys think in terms of db loss/gain when working with RF systems?

...the 402K kit, only works if there is a cable box connected and powered up for the line being tested. As I recall, the 402K indicated the active line from the DC voltage of the cable box output.

That's completely wrong. The 402K is simply a toner and probe. The CATV version toner has a cable and "F" connector. Like many toners it can also be used as a continuity and voltage tester. It has LEDs that will indicate when it is connected to a short, DC voltage or line voltage. No way can it tell you if there is a signal on the cable.

By the way, a cable box does not have any kind of voltage on it's output (or input for that matter). It's probably a dead short to DC as are most splitters. That's probably what your 402 toner is showing- a short. If the toner is connected into a splitter that presents a short it is unlikely that you will be able to pick up it's tone with the probe on any cable coming off of it. It's the same situation as trying to tone any shorted cable.

Trumpy, the original question was only how to identify which end of a cut cable is the feed. You are right, there is lots more that comes into play and if that was understood they wouldn't be cutting into a cable to install a splitter to begin with.

-Hal

Hal,
Then how would you explain this?
When I did CATV installs and post wiring of MDU’s back in the early 1990’s, although it was potentially dangerous, a very common way for some techs to locate a disconnected drop was to connect the cable box at the premises, then find the drop in the pedestal or lockbox by “tasting” the cable ends on the tip of their tongue one at a time. The DC would tingle on your tongue similar to a 9-volt battery. This “test” was only possible with a CATV box connected to the line and powered up, It would work for single family residences or even apartment buildings where the lockbox was located many floors below in the parking garage. I hate to admit it, but I did this my self when time was a factor.

AC leakage from the hot or neutral of the line cord to the box housing or chassis for sure. There are always at least caps from both sides of the line cord to the chassis ground. The chassis of course holds the "F" connectors so it is connected to the shields. I'm not sure if there is also a difference of potential between the shield and center conductor or he was picking up a tingle because he was standing on soil or concrete, but that is the cause.

-Hal

Hal,
As I said, it’s been a long time since and I don’t think I have even held a CATV box for many years, so things could be quite a bit different now.

Anyway, my point was though, regardless of the source, there was a distinct voltage or difference in potential that existed on the line only when a CATV box was installed. True, this in no way verifies that signal is present, but it can be used to locate a cable end.
I don’t think the OP was really interested so much in actually testing for the presence or quality of signal as he was in just identifying the line-in and getting the correct cable connections at the splitter in the attic to avoid having to make several trips up there.

Yes, we do And VSWR and impedance matching cabling and connectors to waveguide, though I didn't get into that with my home CATV. All my calcs were in dB, I just did a quick conversion to % for that post, though. Sounds more dramatic to say each jack gets 1% than to talk about a -20dB loss, ya know?

Hmm, every Motorola/GI cable-box we've had has had about 5VDC to from shield to center, and we're talking 10 boxes here. Hmm, maybe that's why they all quit working...

I can't wait until Cisco (who owns Scientific Atlanta) to buy out Motorola's cable-box/modem division, so I can finally get a box that works, that doesn't need unplugged everyday. (Or dropped out a second story window.)

Ian A.

Will that cure the buggy software issues that some motorola boxes have. Or will that be 3rd party software with cisco too.
We sure have a lot of issues with the firmware upgrades on the HD satellite boxes here.

1. You could carry a cable modem up there and watch the receive led.

2. You could cut the cable, put on your ends, then put in a barrel and a 50 foot length of cable on one end at a time, and take it down to a TV.

1. You could carry a cable modem up there and watch the receive led. 2. You could cut the cable, put on your ends, then put in a barrel and a 50 foot length of cable on one end at a time, and take it down to a TV.

Come on now! You have a 50-50 chance of getting it right the first time you try it. If you are going to go through all of that trouble isn't it going to make more sense to just climb down and see if it works then go back and swap the connections if it doesn't?

-Hal

Ian, Cisco has their feet in every industry now since the computer geeks like them so much. They are doing a very good job of practically destroying the telecommunications industry and making billions in the process. They might make good network hardware (I don't disagree), but the rest of their products are cheap Chinese-made junk.

Wow, a simple question about an inexpensive COAX tester went into four pages? Are we putting too much effort in side-tracking the original question?

Well you gotta figure, Cisco owns SA, SA technically makes the equipment (which I believe is made in Mexico.) What I heard is they want to merge the lines, which could go either way, SA-branded Motorola cable boxes that work, or Motorola-branded SAs that are junk. And in case anyone's wondering, I'm comparing my family's current and past Motorola/GI boxes to my cable-engineer-uncle's current 4 SA boxes, which are all "experimentals" from Comcast. His boxes always work fine, while ours get swapped about every two years.

Just my 2¢
Ian A.

No. What will actually happen is that the box will continue to crash even with Cisco's name on it. Some poor slob at the cable company will open a TAC case with some guy who can barely speak english, and after 5 hours of that guy going through every troubleshooting flowchart Cisco has, they will finally determine that it's a firmware problem and a month later they'll release new firmware that hasn't been fully tested, so the customer can beta-test it for them on a production network.

Like I said, all I know is that all the SA (Cisco) boxes I've seen have worked fine for years and continue to work fine, while the Motorolas we have here are complete junk and last six months at best.

Ian A.

Those SA boxes were designed long before Cisco got their grubby hands on SA.

Cisco has their own issues. I'm sick of dealing with them. If I never have to open another TAC case I'll be happy.

Hmm, one of them was a new model, but that was a year ago.


Ian A.