Too many Unlabeled Antennas

abross · #1 (**permalink**) 10-06-2009, 08:44 PM

So I'm having a slight problem. At my EMS station, I'm helping our chief out with our EOC (Emergency Operations Center); mainly the radios. Well there a couple dozen antennas on the roof of all different categories, and the genius who installed them didn't label any of them. So now I need a way of figuring out which antenna is connected to which cable way down in the radio room in the basement. Are there any simple ways of doing this? I'm hoping to do this without unscrewing the cables from any of the antennas. I did find one by wrapping a coil of wire around the antenna and hooking the wire up to a voltmeter. I then transmitted and figured out which one gave the most voltage. I wanted to know if there is any other way. Thanks. I'll post some pictures sometime soon.

n5ims · #2 (**permalink**) 10-06-2009, 09:14 PM

You could use a telephone line tracing set such as this --> Tone Generator, Triplett 3399 FOX 2 and HOUND 3 KIT which your phone or IT folks probably have. You'll need to unplug one side for the trace (to insert the tones), but the other side can be left connected since it's picked up inductivly.

abross · #3 (**permalink**) 10-06-2009, 09:27 PM

I have seen things like this before, but I don't currently have access to one. I was looking for a possible solution I can use without any fancy tools. Something I can do with various things I may have laying around.

gewecke · #4 (**permalink**) 10-06-2009, 09:35 PM

Try using a MFJ 269b antenna analyzer? Many radio gurus have them. They will allow you to determine where each antenna is resonant without transmitting.
N9ZAS

TheJerk · #5 (**permalink**) 10-06-2009, 09:41 PM

Why not just jumper across the center conductor and shield and then use an ohm meter to determine which one you "shorted"?

abross · #6 (**permalink**) 10-06-2009, 09:43 PM

Not really what I need. I need a way to identify which antenna is connected to which cable. All without disconnecting the cable from the antenna. And I want to be able to do this without spending any money. Just using things around the house.

gewecke · #7 (**permalink**) 10-06-2009, 10:10 PM

I am surprised that your EMS agency doesn't have a reputable service system in place to maintain your company communications hardware?
N9ZAS

abross · #8 (**permalink**) 10-06-2009, 10:21 PM

True. I mean, this isn't something that has to be done, but when it comes time to start moving radios or antennas, it would be nice to know what's hooked up to what.

DPD1 · #9 (**permalink**) 10-07-2009, 12:54 AM

This would probably work using the outer shield and connector housings.

Gardner Bender Wire Tracker Wire Tracer GET-4110K - eBay (item 330337753529 end time Oct-12-09 18:42:00 PDT)

Other than that, if it's not too long a run, you could maybe use a $5 continuity tester with extra wire and run it up to the roof. But if it's too far, it might not have enough juice to light the bulb. Plus, you probably still want to disconnect the radio.

code3cowboy · #10 (**permalink**) 10-07-2009, 01:33 AM

Short a piece of coax, then check all of them on the roof. The antenna you put back on is the antenna connected to whichever radio you plug back in.

TheJerk · #11 (**permalink**) 10-07-2009, 09:25 AM

Quote:

Originally Posted by code3cowboy

Short a piece of coax, then check all of them on the roof. The antenna you put back on is the antenna connected to whichever radio you plug back in.

This is more/less what I told him to do, and he didn't want to hear it...

abross · #12 (**permalink**) 10-07-2009, 09:28 AM

TheJerk, I read what you said, and I had already considered that as a possibility, but the chief doesn't want me to disconnect the cable from any antenna. I wasn't ignoring you, I just can't do it. I just wanted to know if there was a way of accomplishing the same thing another way other than my coil of wire and voltmeter method.

N_Jay · #13 (**permalink**) 10-07-2009, 09:51 AM

First check each line at the radio end for DC open or short with an ohmmeter.

For each open line apply a DC voltage current limited.
a 12 V supply running through a 12V flashlight bulb or small automotive market bulb works well.

Go up and find the antenna that has DC on the elements measured to the shield.

For those that show a short it is a bit harder (but now you have fewer to worry about).

Apply a very low power RF signal. Maybe use the guts from a kids tow walky talky as a source.
Go up on the roof with a receiver with almost no antenna and you shoul easily tell which is which.

P.S you can just do the second, but why not rule out a few the DC way first.

Have fun.

Thayne · #14 (**permalink**) 10-07-2009, 01:46 PM

Two other guys & me, Just spent 2 days doing it the old fashioned way, following the hard lines out of the equipment, thru the racks, thru the bulkhead, up the tower, to the antennas. Put tags at both ends and at the bulkhead. (on the polyphasers) Took pictures, documented everything including antenna type. Found and confiscated 3 unauthorized repeaters.

A real pain in the ass, but the company that bought the site paid us really well.

Also found out I can't climb worth a crap anymore.

DPD1 · #15 (**permalink**) 10-07-2009, 02:25 PM

Better yet, how about just getting the guy who did it all to come back and figure it out.

abross · #16 (**permalink**) 10-07-2009, 02:54 PM

N_Jay, thanks. That was what I needed. Simple yet effective.

Quote:

Originally Posted by DPD1

Better yet, how about just getting the guy who did it all to come back and figure it out.

Unfortunately, the guy who did all this in the beginning, who I still have yet to meet, won't ever come in to do the jobs we asked him to do. Granted, he is a volly, just like me, so he's not obligated, but it would be nice if he would come and help. I've only heard stories about him and have learned the hard way that I should never mention his name around like half the department.

Thanks everyone for all your input.

rvictor · #17 (**permalink**) 10-08-2009, 12:00 AM

The toner and probe suggested in a prior post seem like the only really efficient way to do this. I'd see if I could borrow one from a phone, cable, burglar alarm, etc. installer. I'll bet someone in your organization knows someone that's got one and would loan it out for a good cause for the day.

They might even have them at places that rent tools to do your own home improvement projects given the number of people that are running their own wiring for everything from burglar alarms to home theater.

Dick

abross · #18 (**permalink**) 10-08-2009, 05:52 PM

True. Thanks for the advice.

Don_Burke · #19 (**permalink**) 10-08-2009, 06:44 PM

I would mark everything as it sits with each cable ending up with a tag identifying what it is supposed to be connected to.

Since the chief does not want any antenna disconnected, you can wait until you can hand-over-hand the cables, take advantage of any time a cable has to be disconnected for other reasons or go with the low signal method.

A wireless thermometer puts out a pretty low signal and you might be able to borrow one of those.

abross · #20 (**permalink**) 10-08-2009, 07:23 PM

I do have a frequency generator. I could disconnect a cable from one of the radios and connect the generator to the cable then go on the roof with a walky talky and see which antenna causes the radio to recieve. Thanks.