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Author Topic: 110 Circuit in the same under ground PVC as Coax to tower  (Read 524 times)

NT6U

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110 Circuit in the same under ground PVC as Coax to tower
« on: October 23, 2021, 05:51:27 PM »

Will I experience RFI / Noise / or problems,  by installing a 110 circuit inside the same schedule 40 PVC run that will have the two runs of LMR 600 and Rotator cable to tower I am installing?  PVC run will be roughly +/- 90 feet long & 12" underground x 2-1/2" PVC.  Tower is 70 foot motorized retraceable tower, so power to the tower is needed.
Thanks Gents.
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K6AER

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #1 on: October 23, 2021, 06:23:16 PM »

Providing there are no common mode currents on the coax...no.

LMR series coax has a minimum 90 dB of isolation to the outside world.

We have not had 110 volt AC delivery for over 70 years. Today's single phase voltages are a minimum of 120 or 240 VAC from the power companies.
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N2SR

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #2 on: October 24, 2021, 02:55:29 AM »

You may want to find out what the code is for electrical wiring before you do that. 

Many municipalities require a separate conduit for AC wiring. 


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Elect a clown.  Expect a circus.

K1VCT

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #3 on: October 24, 2021, 06:30:08 AM »

I can some old school thinking.... with 110v terminology.  Most of us have 120v-125v, even me out in the sticks ;)

Some thoughts that cross my mind....

Seems like 2-1/2 inch PVC is a bit overkill for LMR-600.  Maybe, in the same trench, something more like 1-1/2 for the LMR-600, and 3/4 for the wiring. 

For that matter, you didn't specify the frequency ranges you'll be using, and for HF LMR-600 is just not needed for the length you're using.  For UHF, there's only 1dB difference at 100' between LMR-400 and LMR-600 at 450mHz.

I'm curious if you'll be transitioning to more flexible cable for the tower itself.  LMR-600, even the UltraFlex is pretty stout and doesn't bend all that easily.  And of course, watch you're bend radii on the runs and transitions.

No affiliation, but I strongly suggest the use of the Times "EZ" connectors for that LMR-600, and also using Type-N instead of PL-259/SO-239 "UHF" connectors, just for the weather sealing of the connector if nothing else (price is the same for either type by the way).

Although the conduit is "supposed" to be dry inside... it usually isn't.  You might want to consider the "DB" variety.  For that matter type UF for the 120v power.
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WA1UIL

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #4 on: October 24, 2021, 07:12:19 AM »

Whats the voltage rating on the coax and rotor control wires? That'
s where the problem will be.
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K6AER

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #5 on: October 24, 2021, 07:38:32 AM »

If you are not going through the Electrical Code route, then just put a plug on the AC feed point. Then your electrical feed to the tower base is just an extension cord.
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NT6U

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #6 on: October 24, 2021, 08:34:49 AM »

We have not had 110 volt AC delivery for over 70 years.
I will measure my voltage before I post again.  You are 100% correct !!!
Thank you
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G4AON

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #7 on: October 24, 2021, 08:38:47 AM »

Here in the UK, 12 Volt vehicle winches are popular with telescopic tower owners. See:
https://www.davidbowyer.co.uk/rad-winch.html

73 Dave
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NT6U

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #8 on: October 24, 2021, 09:20:23 AM »

Thanks for all's interest & reply's.  I intend to follow all NEC code without question as my project is permitted through Mohave County AZ.  I am installing a LMR 470 tower, the motor to crank up is 110 AC +/-
The Rotator is a new YAESU G-2800DXA.
The tower is nearly 70 feet from house.  The run of coax & rotator cable is about 100 feet from house to tower base.  I have 3, KF7P entrance panels with rotator and Morgan arrestors.  2 panels at house 1 panel at the tower.  Due to 7/8" hardline availability I did best I could and am running two permanent LMR 600 runs buried in ground from House entrance panel to the tower entrance panel.  I'll run LMR 400 or 213 from tower panel up to antenna. (open to suggestions). 
The house entrance panel is right against new station hence I built and designed the house with this in mind.
New Base from Carl @ Tashijian Towers is now set in concrete rebar and framing, & concrete done by me.  So far so good !!! I'm an retired Union Carpenter having a blast on this project yet I need help on stuff I don't know.
Thanks for all CONSTRUCTIVE feedback


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WA1UIL

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #9 on: October 24, 2021, 09:38:09 AM »

A GFCI would be a nice touch, or just stand in a plastic pail when touching the tower :)
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W7CXC

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #10 on: October 24, 2021, 09:39:46 AM »

Really? 110, 115,120,.....121.739 VAC. Didn't we all understand the question?

IMHO go with separate  conduit or better yet just use direct bury coax.  Unless there are weep holes in the conduit it well eventually get standing water  depending on your climate ect.

M&P Airborne 10 coax has about 115db isolation as i recall 73's
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W9IQ

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #11 on: October 24, 2021, 10:11:01 AM »

In the end, it isn't what NEC says, it is what your local inspector says. So before you start construction of the mains run, check with your local inspector about co-locating the UF-B with other cables. You will likely need to have conduit on the UF-B where it enters and exits the ground in any case - typically 18 inches into the ground.

Don't forget that you will also need to bond the tower ground to the house ground. Plan the ground cable in the same trench. A few ground rods along the way in the trench would be a good idea. Use exothermic bonding for these rods. While tying grounds together, plan a ground connection for your shack common equipment ground.

Plan your lightning arrestors at the tower end tied to the tower ground system. If you wish to be extra cautious, you could install additional lightning arrestors at the house end before the coax enters the house. If you plan on using any remote antenna switches or remote antenna tuners that rely on voltage injectors, make certain to use compatible (non DC blocking) lightning arrestors.

Do consider that any noise on the UF-B cable may be induced into and on the coax cable regardless of the dB of isolation of the coax cable. Placing common mode chokes on the coax as it enters and exits the ground may help on the HF bands. Under extreme circumstances, a UL listed common and differential mode filter may need to be installed on the mains run as it leaves the main panel.

Good luck with the project.

- Glenn W9IQ



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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

N9EYL

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #12 on: October 24, 2021, 10:36:36 AM »

I'll just chime in to say more or less what the last poster said.  NEC doesn't allow for buried power to be mixed with signal like coax or CAT5.  The idea being that AC could get shorted through water or a nick in the cables.  And since workers don't expect there to be any dangerous AC on a signal cable they could get shocked.

Cable in conduit should be of the waterproof variety; thWn not thhn.  You should always assume that buried conduit will be water filled.

It's always up to the locality and the inspector of the day.  This varies so widely it's flat out laughable. If you could get by with it, mixing signal and power saves a lot of work and digging.

Many localities allow burial grade 110V Romex without conduit.  The grey stuff.  You should never bury the yellow stuff with the paper in it or even put it in underground conduit.  I personally hate the grey stuff without conduit because it kinks and is hard to work with and works it way up over time.  But it can be legal.

Also, and I know you know this. But, no connectors in the underground run because of the water.

Me personally, I would run a fat pipe.  I've NEVER regretted running a pipe that was too big.  But, I have run conduit that was the "right" size at the time only to later regret it.

Also, unless you just hate your future self, run a nylon cable for future pulls.  You know you are going to pull something in the future right? 

Good Luck!
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NT6U

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #13 on: October 24, 2021, 12:02:46 PM »


Also, unless you just hate your future self, run a nylon cable for future pulls.   
That is a brilliant thought !! 
I will try to post a few pics on QRZ of the mess I'm making. 
I really appreciate the feedback to date from all.
Thanks
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AA4PB

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Re: 110 Circuit in the same under ground PVC as Coax to tower
« Reply #14 on: October 24, 2021, 01:34:05 PM »

The NEC (which most inspectors follow) does not permit the mixing of low voltage and high voltage cables in the same conduit. However, if you run the coax in PVC conduit then you could put UF (underground feeder) electrical cable outside of the conduit but in the same trench, provided it is deep enough (24-inches).

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Bob  AA4PB
Garrisonville, VA
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