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Cable tracing through a building
We have a piece of RG6 Quad in one area of a building and we can't seem to find the other end of it. I thought that I knew where it went as I installed all these cables, but it's just not there. I have a small tone generator and an inductive probe that work well on unshielded wire, but attempts at using this on shielded cable have always been a problem. I've been thinking of trying to set my old HP200CD audio oscillator to 1KHZ and really crank it up and feed it into the cable. The 200CD will output a respectable signal across 600 ohms, (naturally I'd be using it unterminated here), and I wonder if I'd be able to pick it up through the cable then?
The only other thing I can think of,(and this is probably not very practical) is to inject a high enough RF frequency into the cable at a level where it would egress. Perhaps I might be able to see this on my spectrum analyzer. Of course I realize that the superior shielding of the quad cable is working against me here too. I know that there must be equipment designed to do this, but I'm not really in a position to make a purchase like that. Does anyone have any suggestions for finding this cable? Thanks, Lenny |
Cable tracing through a building
John Robertson sendte dette med sin computer:
On 11/19/2013 11:00 AM, wrote: I know that there must be equipment designed to do this, but I'm not really in a position to make a purchase like that. Does anyone have any suggestions for finding this cable? Thanks, Lenny Use a spark generator tied to the shield and an AM pocket radio...if you have an old Model T Ford ignition coil (OK, my junk box, what's in yours?) that makes a great noise generator. The AM radio will happily track the wire antenna... I guess he wants to use the cable again, without having the insulation burnt by sparks But I'm using the same trick when finding breaks in the loop for my automatic lawnmower. I can usually hear the spark even if it is underground. I'm using an electric cattle fence generator, around 6kW. Leif -- Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske beslutning at undlade det. |
Cable tracing through a building
On Tue, 19 Nov 2013 11:00:38 -0800 (PST),
wrote: We have a piece of RG6 Quad in one area of a building and we can't seem to find the other end of it. You need to use a higher frequency in order to get any kind of range. I suggest you find a function generator that covers the AM broadcast band. Make sure it's modulated so you can hear the signal on an AM portable radio. Connect the RG-6u to the generator with the coax connections BACKWARDS as in generator ground to the coax center, and generator hot to the coax shield. That turns your RG6/u shield into an antenna. You may have some problems if the other end of the coax is grounded, but that just means cram in more signal. Then, fumble around with the portable radio until you get signal. Also, it might be useful to check if there's any DC on the coax, just in case it's connected to a DBS receiver. One problem with this method is that you can easily end up with too much range. I used this method once to locate some RG-6/u in a large house. I thought I had the signal in one room, only to find that the cable was really going through the wall in the adjacent room. Play with the signal levels. There are other frequencies that will work, but the BCB seems to be the easiest. If your portable radio has a loopstick, you can play direction finder. I've had marginal success with DF, but it might be worth a try. If all else fails, just apply 117VAC to the coax. Whatever device explodes is the other end of the coax. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Cable tracing through a building
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Cable tracing through a building
On 11/19/2013 1:58 PM, Jeff Liebermann wrote:
On Tue, 19 Nov 2013 11:00:38 -0800 (PST), wrote: We have a piece of RG6 Quad in one area of a building and we can't seem to find the other end of it. You need to use a higher frequency in order to get any kind of range. I suggest you find a function generator that covers the AM broadcast band. Make sure it's modulated so you can hear the signal on an AM portable radio. Connect the RG-6u to the generator with the coax connections BACKWARDS as in generator ground to the coax center, and generator hot to the coax shield. That turns your RG6/u shield into an antenna. You may have some problems if the other end of the coax is grounded, but that just means cram in more signal. Then, fumble around with the portable radio until you get signal. Also, it might be useful to check if there's any DC on the coax, just in case it's connected to a DBS receiver. One problem with this method is that you can easily end up with too much range. I used this method once to locate some RG-6/u in a large house. I thought I had the signal in one room, only to find that the cable was really going through the wall in the adjacent room. Play with the signal levels. There are other frequencies that will work, but the BCB seems to be the easiest. If your portable radio has a loopstick, you can play direction finder. I've had marginal success with DF, but it might be worth a try. If all else fails, just apply 117VAC to the coax. Whatever device explodes is the other end of the coax. This won't help the OP, but it is a technique I have used to find buried coax several times and it has worked every time. With a portable AM radio, position the radio on it's backside and rotate it until you find a null in the audio. This is how you want to lay it on the ground, now as you move it over a coax in the ground the radio signal will be disturbed and the null will be lost and audio will appear. I have followed 40ft of coax with this method. I love it, saw it somewhere on the net. Mikek Tune a portable AM radio to a *station that when you rotate and find the null, (all audio disappears) |
Cable tracing through a building
I really like the AM radio idea in conjunction with a noise source, and while I don't have a Ford coil around I'm sure that I could come up with a coil and some type of interrupter to do the spark. However as was mentioned in the thread, using 15KV I don't want to blow a hole through the cable either. That might make a few nice unwanted notch filters for God only knows what frequencies...
The EM door buzzer sounds like a pretty non destructive idea, but how would I connect it to the cable? I just noticed Jeff's idea of using an RF frequency, modulated it seems with some sort of waveform on the AM band. I especially like that idea and in fact was just considering throwing it out there when you posted it Jeff, but with one exception. I have a function generator, but I don't know if it will cover this band. I also have an AM signal generator that unlike my boat anchor Marconi, is portable. I can internally modulate it at 400HZ. I understand the procedure you've outlined reversing the shield, levels, etc, so why couldn't I use a standard AM signal generator? The answer to the other suggestion posted about using two shields is also interesting, however the term "quad" does not describe four cables but rather a description of the shield on one cable. Lenny |
Cable tracing through a building
"Leif Neland" wrote in message ...
I'm using an electric cattle fence generator, around 6kW. Did you mean 6kV? You aren't trying to grill the beef on-the-hoof! |
Cable tracing through a building
Is the destination end "dangling" -- that is, exposed and not connected to
anything? If so, just stick a battery on the other end and start measuring. |
Cable tracing through a building
On 11/19/2013 12:48 PM, wrote:
I really like the AM radio idea in conjunction with a noise source, and while I don't have a Ford coil around I'm sure that I could come up with a coil and some type of interrupter to do the spark. However as was mentioned in the thread, using 15KV I don't want to blow a hole through the cable either. That might make a few nice unwanted notch filters for God only knows what frequencies... The EM door buzzer sounds like a pretty non destructive idea, but how would I connect it to the cable? I'm not certain, but I suspect that if you simply connect one end of the cable to a lead near the noisy contacts that the wire would then act as an antenna. Also, the 15KV would only puncture the insulation if it formed a path, so if you connect all the conductors/sheilds to the same point source and that risk vanishes, and don't ground the other side of the coil - it is simply a spark gap transmitter at this point. Now I haven't tried any of these ideas, just recall them from old electronics and wiring books I've read over the years. YMMV John :-#)# I just noticed Jeff's idea of using an RF frequency, modulated it seems with some sort of waveform on the AM band. I especially like that idea and in fact was just considering throwing it out there when you posted it Jeff, but with one exception. I have a function generator, but I don't know if it will cover this band. I also have an AM signal generator that unlike my boat anchor Marconi, is portable. I can internally modulate it at 400HZ. I understand the procedure you've outlined reversing the shield, levels, etc, so why couldn't I use a standard AM signal generator? The answer to the other suggestion posted about using two shields is also interesting, however the term "quad" does not describe four cables but rather a description of the shield on one cable. Lenny -- (Please post followups or tech inquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
Cable tracing through a building
On Tue, 19 Nov 2013 12:48:55 -0800 (PST),
wrote: I really like the AM radio idea in conjunction with a noise source, and while I don't have a Ford coil around I'm sure that I could come up with a coil and some type of interrupter to do the spark. Ummm, I said function generator or maybe RF generator. In case you haven't heard, spark transmissions are banned by the FCC. However as was mentioned in the thread, using 15KV I don't want to blow a hole through the cable either. That might make a few nice unwanted notch filters for God only knows what frequencies... It would melt the insulation and cause a short as the center conductor migrates towards the shield on corners. The EM door buzzer sounds like a pretty non destructive idea, but how would I connect it to the cable? Clip leads. I have a function generator, but I don't know if it will cover this band. Most function generators will go to 1MHz. I also have an AM signal generator that unlike my boat anchor Marconi, is portable. I can internally modulate it at 400HZ. Good enough. I understand the procedure you've outlined reversing the shield, levels, etc, so why couldn't I use a standard AM signal generator? I didn't know you had an RF generator. Whatever you have. Just don't use a 100 watt HF transceiver. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Cable tracing through a building
On Tue, 19 Nov 2013 14:18:37 -0600, Jon Elson
wrote: wrote: We have a piece of RG6 Quad Quad means 4 coaxes in a jacket? Quad means quad shielded or 4 shields. The idea is to reduce cable TV leakage and ingress. Quad shielded is usually used on the poles for CATV. The in-building distribution stuff is usually double shielded (foil+braid). They will be labeled RG-6A/U for double and RG-6A/UQ for quad. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Cable tracing through a building
I have gotten a lot of great ideas guys. I'll give it a shot. Thanks for all the help. Lenny
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Cable tracing through a building
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Cable tracing through a building
wrote:
wrote: We have a piece of RG6 Quad in one area of a building and we can't seem to find the other end of it. I thought that I knew where it went as I installed all these cables, but it's just not there. Don't discount the possibility that somebody cut it short and shoved the end back into the wall, or up above the suspended ceiling, or whatever. If they shoved it back in the wall and that wall has since been painted or otherwise remodeled, there might not even be a hole in the wall anymore. I have a small tone generator and an inductive probe that work well on unshielded wire, but attempts at using this on shielded cable have always been a problem. Try putting the -/black lead of the tone generator to earth ground (like powerline ground at an outlet) and the +/red lead to the *shield* of the RG6. Then use the inductive probe like normal. I might be a good idea to test for continuity to ground at the unknown end before some of the suggested tests to find out it somethink is connected to it. |
Cable tracing through a building
On Wed, 20 Nov 2013 07:47:41 -0700, Bob F wrote:
...snip... I might be a good idea to test for continuity to ground at the unknown end before some of the suggested tests to find out it somethink is connected to it. some usually gets through even if 'grounded' However, better if possible to inductively couple to the shield, less load for your source. Or, just tap into the shield about a foot away from the grounding. |
Cable tracing through a building
William Sommerwerck wrote:
"Leif Neland" wrote in message ... I'm using an electric cattle fence generator, around 6kW. Did you mean 6kV? You aren't trying to grill the beef on-the-hoof! http://www.coalcanal.org/other/images/Cattle.jpg -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
Cable tracing through a building
I'm using an electric cattle-fence generator, around 6kW.
Did you mean 6kV? You aren't trying to grill the beef on-the-hoof! http://www.coalcanal.org/other/images/Cattle.jpg That looks more like "spontaneous bovine combustion". |
Cable tracing through a building
Lenny, please be sure to tell us what you end up doing and if you are successful.
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Cable tracing through a building
On 11/19/2013 01:10 PM, William Sommerwerck wrote:
Is the destination end "dangling" -- that is, exposed and not connected to anything? If so, just stick a battery on the other end and start measuring. http://www.ebay.com/sch/i.html?_fspt...t+fox&_rdc= 1 At least get the receiver part. Use a sweeping or warbling tone for fast positive ID. |
Cable tracing through a building
"dave" wrote in message
m... On 11/19/2013 01:10 PM, William Sommerwerck wrote: Is the destination end "dangling" -- that is, exposed and not connected to anything? If so, just stick a battery on the other end and start measuring. http://www.ebay.com/sch/i.html?_fspt...t+fox&_rdc= 1 At least get the receiver part. Use a sweeping or warbling tone for fast positive ID. My point in suggesting DC is that there's no inductive coupling to confuse identification. |
Cable tracing through a building
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