Cable Installation in Metal Conduit

[DownEastNC]

I'm considering getting a sectional mast system, actually a flag pole, and running the coax inside the pole and mounting the antenna at the top. Is there anything inherently wrong with this approach? It's an 11 gauge 6005 aluminum. Here's a link to the mast system; https://oldgloryflagpole.com/sale-page1

Edited October 4, 2021 by DownEastNC
addl info

[mbrun]

I'm considering getting a sectional mast system, actually a flag pole, and running the coax inside the pole and mounting the antenna at the top. Is there anything inherently wrong with this approach? It's an 11 gauge 6005 aluminum. Here's a link to the mast system; https://oldgloryflagpole.com/sale-page1

There is nothing inherently wrong with running the coax inside the pole, be it a metal or fiberglass mast. It is really no different than running the feed line in conduit. It could make for a nice looking installation.

Be aware that if the mast is collapsible you must have provisions at the bottom to evacuate excess feed-line when mast is collapsing. Different considerations are necessary if it is a tilt over.


Michael
WRHS965
KE8PLM

[DownEastNC]

Thanks Michael,

I didn't know if there were going to be any signal radiation / degradation problems by running the coax in a metal pipe. So it sounds like a go and yes the appearance will be much better with the wires hidden, which is why I want to do this in the first place. I'm going to come up with some sort of system to be able to fold the mast over and re-erect it with a means to prevent the coax from getting stressed. I'll have to get the mast system in front of me before I can engineer that option. I'm looking forward to this as I desperately need to get an antenna up in the air.

I have a follow up question; If I were to run another coax, say for an off the air TV antenna in that conduit, do you think there would be any crossover problems, the radio interfering with the TV and so on? I would mount the OTA antenna at a different vertical elevation of course.

Thanks

Mike / WRNV336

[wqpn591]

How will you feed the coax into the center at the bottom without drilling a hole in the side of the mast? Assuming this goes into the ground a bit for stability, the coax would need to be direct burial if its in the ground.

[DownEastNC]

31 minutes ago, wqpn591 said:

How will you feed the coax into the center at the bottom without drilling a hole in the side of the mast? Assuming this goes into the ground a bit for stability, the coax would need to be direct burial if its in the ground.

Short term the mast will be attached to my storage shed and the bottom of the mast will be elevated off the ground. I'll use flat bar brackets and right angle pipe clamps for that. Long term I'll set a utility pole in the yard and mount the mast on top of that with some sort of gin pole contraption to be able to fold and stand up the mast from the ground.

Edit: For those that want to set the mast on a concrete footing, you could stub a piece of PVC electrical conduit and a 90  degree fitting beneath the concrete into the mast ground sleeve. Of course you would have to come up with a way to have some slack in the coax if you wanted to disassemble the mast. It's your option if you want to continue the conduit to its destination or just direct bury it. I personally would opt for the conduit to avoid having to dig up wire if there were a need to replace / upgrade it.

[mbrun]

Thanks Michael,
I didn't know if there were going to be any signal radiation / degradation problems by running the coax in a metal pipe. So it sounds like a go and yes the appearance will be much better with the wires hidden, which is why I want to do this in the first place. I'm going to come up with some sort of system to be able to fold the mast over and re-erect it with a means to prevent the coax from getting stressed. I'll have to get the mast system in front of me before I can engineer that option. I'm looking forward to this as I desperately need to get an antenna up in the air.
I have a follow up question; If I were to run another coax, say for an off the air TV antenna in that conduit, do you think there would be any crossover problems, the radio interfering with the TV and so on? I would mount the OTA antenna at a different vertical elevation of course.
Thanks
Mike / WRNV336

If the cables are poorly shielded, yes, the potential exists that when transmitting you could get some leakage into your over-the-air antenna coax. I would suggest RG-6 or RG-11 quad-shielded coax for your TV coax, the same high-grade stuff that the cable TV utility should be using as drop cable to your home.

The bigger issue you may have to contend with if you are thinking of putting both antennas on the same mast, is actually over-the-air leakage from your GMRS transmitter getting into your antenna. If a family member is not watching TV and/or you are not DVRing a show it may not be an issue. I have been known to mess up a recording or two while talking on the radio at my place.


Michael
WRHS965
KE8PLM

[AdmiralCochrane]

I run my coax to my triband antenna exactly as DowneastNC suggests.  My UHF element is resonant enough to give OK SWR on GMRS.  I think it was actually 1.11:1 on 440 and 2.10 on GMRS.  I recently upgraded the coax to LMR600, but I should actually bump it up another 5 ft; right now its about 40 ft up. 

[nekpop]

I mounted my gmrs base antenna atop a 30 foot flagpole and have coax fed down inside pole. I cut an exit hole in the pole and installed a grommet to protect the coax. It works great.

[SteveShannon]

1 hour ago, nekpop said:

I mounted my gmrs base antenna atop a 30 foot flagpole and have coax fed down inside pole. I cut an exit hole in the pole and installed a grommet to protect the coax. It works great.

That’s pretty nice!  I’ve been considering getting a flagpole anyway.

One thing though, that RG-8x attenuates a lot of signal at GMRS frequencies. You might want to consider upgrading to LMR400 at some point.

[LeeBo]

2 hours ago, nekpop said:

I mounted my gmrs base antenna atop a 30 foot flagpole and have coax fed down inside pole. I cut an exit hole in the pole and installed a grommet to protect the coax. It works great.

Very nice.  I wonder if this could be used as a "work around" for HOA's.  

[WRXB215]

@LeeBo I've heard of people doing exactly that.

[nekpop]

On 9/13/2024 at 10:57 AM, SteveShannon said:

That’s pretty nice!  I’ve been considering getting a flagpole anyway.

One thing though, that RG-8x attenuates a lot of signal at GMRS frequencies. You might want to consider upgrading to LMR400 at some point.

That’s true but what makes HMR 400 better when it comes to attenuation is double shielding. Routing the coax inside the metal flagpole accomplishes the same thing. I have a 40 ft run but 30 ft of that is inside the metal pole. Loss is minimal and I have a lot less weight hanging on the connector to my an antenna. I have been pleased with the performance.

[nekpop]

33 minutes ago, nekpop said:

That’s true but what makes HMR 400 better when it comes to attenuation is double shielding. Routing the coax inside the metal flagpole accomplishes the same thing. I have a 40 ft run but 30 ft of that is inside the metal pole. Loss is minimal and I have a lot less weight hanging on the connector to my an antenna. I have been pleased with the performance.

I meant LMR400….don’t know where the “H”came from.