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Inside antenna and grounding

Jul 24th 2012, 21:14


Joined: May 24th 2012, 23:18
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I want to at times use an antenna made from ladder wire for GMRS frequencies inside of my home. It will be used with a 120VAC plug in power supply connected to a 13.8 VDC radio with the antenna hanging in the highest part of the living room.
Will this still need grounding?

I'm leary of near by lightning hits putting high voltage into the antenna (even inside my home) and of course there is always static electricity that may damage my equipment.

I don't know if the grounded plug on the power supply with the radio chassis connected to the chassis of the power supply will be enough or if it might put my electrical system in the home and radio equipment at risk.

I will of course take the antenna down and un plug it during electrical storms, just want to be safe and not ruin my equipment either, the issue of static electricity picked up by the antenna is a worry as to hurting the electronics.
I may have answered my own question (ground it), but want opinions from others.

Thanks, John K
Jul 25th 2012, 17:16


Joined: Apr 4th 1998, 00:00
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In most instances no additional grounding would be necessary for an inside antenna. I'm not clear on your use of ladder line for GMRS frequencies. GMRS frequencies would be in the 460 Mhz range. I would guess the radio would be an amateur UHF or possibly commercial UHF radio that would commonly have an SO239 antenna connector on the back of the radio. What are you using to adapt the ladder line to the SO239 connector on the radio?

A lightning surge to your homes electrical system can cause damage to any device that is "plugged in". Many people install surge suppressor devices to protect their equipment. In some areas the Power Company offers to install these devices to your electrical system for a small monthly fee. Connecting an indoor antenna to your radio does not increase (or decrease) the possibility of a surge to your electrical system.

ARRL Technical Coordinator - Kansas Section
Jul 27th 2012, 04:03


Joined: May 24th 2012, 23:18
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The antenna, made from 300 ohm twin line is one being manufactured by and it has a "N" connector on the end that will be connected to a commercial radio with a SO239-SO259 on the other end using a short run of LMR 240 for inside of the home use. It is being cut to the input frquency of a local GMRS repeater. Thank You for the answer.
I was more worried about induced electricity by near by lightning strikes inducing an electrical charge into my inside the home antenna through the walls, I understand the problem with power coming into the electrical system from commercial power. A surge protector will be used for the commercial power radio equipment and it will be unplugged during storms whenever possible. An outside antenna is in the works and will be properly grounded and fed with LMR 400, the inside twin lead antenna is temp and will also be used for ECOMS.
The UHF is made from the 300 OHM twin lead, the VHF he is making from 450 OHM ladderline for matching purposes. I have not tried out these antennas yet, but for the price it should be a great roll up antenna for GMRS for my go box to go along with the 2M/440 equipment and antennas.

My Best, John

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