I have several antennas on a tower that have coax ran into the building. What would be the best way to trace the coax to figure out which antenna it goes too without climbing the tower? Any suggestions are appreciated thanks.
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Coax Cable Tracing
- Thread starter pepper33
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If they're all at the same height and frequency then not sure how you're going to do that.
If they're at different heights, than a DTF measurement should give you an idea or if they're different bands, a sweep should help.
If they're at different heights, than a DTF measurement should give you an idea or if they're different bands, a sweep should help.
S
They are all different heights. Some are UHF 400mhz, some VHF 150mhz and ive got a couple 700-800mhz Yagis as well.
An antenna analyzer used inside the building should tell you what band the antenna is by showing a low VSWR within its operating band.
K4EET
Chaplain
A good antenna analyzer will also tell you the feedline length. So if you have two VHF antennas, you should also be able to figure out which is which if you know how much coax is used in the shelter up to the base of the tower.
As said hook up a analyzer and run return loss and DTF. That will at least give you a starting point. Sometimes it will come down to a climber or a drone to verify the model number but you can learn alot with sweeps.
ka3aaa
Member
climb the tower and mark the coax with electrical tape or paint every few feet as you go, that way you can inspect the coax and re attach it to the tower if needed, also make a map of the tower while your there. what antenna, freq, and coax type.
I think the OP stated how to without climbing the tower.
QUOTE="ka3aaa, post: 3747115, member: 149038"]
climb the tower and mark the coax with electrical tape or paint every few feet as you go, that way you can inspect the coax and re attach it to the tower if needed, also make a map of the tower while your there. what antenna, freq, and coax type.
[/QUOTE]
QUOTE="ka3aaa, post: 3747115, member: 149038"]
climb the tower and mark the coax with electrical tape or paint every few feet as you go, that way you can inspect the coax and re attach it to the tower if needed, also make a map of the tower while your there. what antenna, freq, and coax type.
[/QUOTE]
There are some tone generators/probes (a la the Telco industry) that can be used with coax. You'd have to take the antennas/coax out of service to test. Also you'd have to start at the base of the coax (no splitters, combiners, etc) The type of antenna connected to the tower end of the coax would likely affect how well this methods works though. The analyzer would be the better bet.
mmckenna
I ♥ Ø
A toner would work, however the OP didn't want to climb the tower.
TDR/or the NanoVNA and check the resonance of the antenna is the easy way to do this without climbing the tower.
Perfect world would be a tower map with the coax cables "phase taped" and identified after install.
If by by chance his antennas were 1/4w GP / with no matching circuitry he might be able to get by without a tower climb. I forget we were in the industrial forum so these are more likely to be cellular sector antennas or something similar.
"Danger Will Robinson" Brain Fart!!!!!! I was thinking that if the was no antenna loading down the toner, there might be just enough bleed through on the skin to detect a signal. (Yes, even though it coax) But again, we're in the industrial antenna forum so hardline is very possible and bleed through is less likely. Even if it did work, it would get the OP any further than he could reach. Well, let the tongue lashing begin.
Couple that with a DTF sweep and you should be able to ID the antennas and feedlines with reasonable accuracy.
Without climbing the tower and measuring the length of each cable, how would you know the antenna from a DTE sweep?
And don’t forget to set the velocity factor, lest your distances will not be what you expect.
The Antennas are currently not being used but will be put in service in an EOC. Antennas are commercial grade most are fiberglass Telewave i think. Any recommendations on an analyzer?
mmckenna
I ♥ Ø
What is your budget?
A good spectrum analyzer with tracking generator is a handy tool to have. Question is, how much do you want to spend?
Easy to blow $10K to $20K on one.
Or, get a NanoVNA off Amazon for less than a hundred bones if you don't expect to use one often. They fall into the "good enough" and "hobbyist" area of quality/cost/usefulness.
I would recommend this for your task at hand. It covers 137MHz to 2.7GHz and should easily identify any VHF/UHF/800/WiFi antenna at the other end of the coax. I've used just about every meter ever made and own quite a few and this one is very easy to use in the graph display mode. You can set it to sweep 137 to about 950MHz and the antenna in question will show what band it covers quickly on the display. You can then narrow the span like 440-470MHz if you find a UHF antenna and it will give more details about the antenna and how it might perform within the amateur bands.
Meters without a graphical display will have you turning knobs and trying to interpret what's going on where this one will just give you an instant answer of where the antenna works. There are other models that cover down to 1MHz but I don't see one advertised at the moment. There are also other sellers that are cheaper but this one has better feedback.
BTW, I have three of these in different frequency ranges, the same 137-2.7GHz model which was their first model, then I got a lower freq version that has two ports and can sweep filters, etc, then I bought a later model that covers everything and sweeps filters, etc. I've been very happy with all of them and most of my other meters now sit on the shelf.
Meters without a graphical display will have you turning knobs and trying to interpret what's going on where this one will just give you an instant answer of where the antenna works. There are other models that cover down to 1MHz but I don't see one advertised at the moment. There are also other sellers that are cheaper but this one has better feedback.
BTW, I have three of these in different frequency ranges, the same 137-2.7GHz model which was their first model, then I got a lower freq version that has two ports and can sweep filters, etc, then I bought a later model that covers everything and sweeps filters, etc. I've been very happy with all of them and most of my other meters now sit on the shelf.
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mastr
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IF this application is an actual "EOC" (actual in this case meaning operated by a first responding agency) my recommendation is to spend the money and time to have a qualified person inspect the tower and identify what is on it.
Above post a good idea. If that's not the case here are a couple screen shots of my little analyzer. First is a wide 135-950MHz sweep to identify where the antenna on my tower might resonate, which is in the 450-470MHz range. The antenna is actually a Scala 450-470MHz Yagi on the tower. The second picture is zeroing in more on the frequency range so see what the useable band width might be.
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