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I have a detached garage that is approximately 15 feet high. The garage is approximately 20 feet from my home I will be using a Kenwood D-710GA radio, a Grandmaster SWR Meter and a 6 foot comet GP-3 antenna.

I’m thinking of using a 2” pipe as a mast. The pipe will be driven 4 feet into the ground and mounted to the concrete side of the garage. I’d appreciate your thoughts on the following: I’ve read an antenna mast should extend 3 foot above the antenna. Is this necessary? I was thinking of terminating the pipe 3 foot higher than the garage and attaching the antenna to this part. The antenna would be 6 foot above the roof of the garage (a three foot overlap of the pipe/antenna). Will this work and be safe? Or, do I have to extend the pipe 9 foot above the roof (6 foot for the antenna and 3 additional feet).

In addition to the pipe being driven into the ground and attaching it to grounding rods is there anything else I can do to make sure the antenna is properly grounded? One last question. For safety reasons I plan to disconnect the coax from the radio when there is a chance of rain. Is there anything else I can do to reduce the possibility of my equipment being damaged or someone being hurt if the antenna is hit by lightning? Thank you for your help Jeff

Can you use 1 antenna mast (pole) for 2 different radio antennas? I understand there should be a 3-foot separation between antennas. However, I am limited to the amount of space I can use.

Here's what I'm thinking. Attaching 2 antennae to opposite sides of the 2" pipe I will be using as an antenna mast. The pole/mast will be anchored to the concrete wall on my garage. Once they antenna are mounted I thought of using multiple tennis balls on each antenna to prevent one from touching the other.

Thank you for your thought on this

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Regarding the overlap of the mast to the antenna, there should be about 1 foot of overlap as shown in this picture:

enter image description here

The top of the pipe must stay below the decoupling radials in order for the antenna to function properly. This puts the top clamp within an inch or so of the top of the pipe.

Keep in mind that on VHF and UHF FM, line of site is key to reliable communications. The higher you can place your antenna, the better.

Regarding other things to think about, here are a few ideas:

  1. Use high quality coax like RG-213 or LMR-400 to reduce losses
  2. Use a VHF/UHF lighting arrestor on the coax at the base of your mast
  3. Bond your ground rods to your house electric service ground
  4. Seal the top of the pipe to reduce water ingress that promotes rusting/freezing
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I would say the mast must extend only high enough to provide appropriate mechanical support. Glenn W9IQ provides a great illustration.

Having the mast extend above the antenna might provide some degree of lightning protection since the mast, rather than the antenna will take most of the strike current. But I'd regard this as a "nice to have" rather than a requirement. In the case of installing a vertical on the mast you'd need to get the antenna horizontally away from the mast. Sometimes you see this on towers, like this one on the KA1RCI repeater network:

enter image description here

However, given you have just a small mast rather than a huge tower, I'd say this is just unnecessary complexity and cost with very little benefit. Instead, I'd recommend following good lightning protection practices.

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