How Close can I install my Greyline Vertical Antenna or Flagpole Antenna to buildings, trees, etc.?

Greetings, Fellow Ham Radio Enthusiasts.

Have you ever wondered how close you can install your antenna to trees, your home, or nearby buildings? We've enlisted the expertise of antenna designer and engineer, John Portune, to explore this question. John conducted a comprehensive worst-case scenario experiment, focusing on an OCF Flagpole antenna near metal siding.

Prepare to be encouraged by John's findings. Read on to discover the valuable insights he gained from his experiment and share your thoughts with us too!

Thank you and 73.

Does it matter where you mount the Flagpole Antenna?

By John Portune (October 29, 2018)

My existing 20 ft. flagpole antenna (4+16 ft. 2 in. aluminum, 1 ft. fiberglass base insulator and 4 in. fiberglass feed point insulator spacing) sits roughly 18 inches from my metal-skinned mobile home. I added a new mount 15 ft. away from the house.

In both locations, I used my VNA to measure the impedance and SWR's at the input of the 5 ft. 450 Ohm ladder line from the base to the feedpoint in three situations.

(1) near the house with a flag,
(2) away from the house with flag and
(3) away from the house without a flag.

The graph below shows the SWR vs. frequency.

Clearly, the flag has no effect. The two curves illustrate with and without a flag, both totally overlap. From 40m and up, the house has only a little effect. On 80m the house increases the SWR. (Greyline: That's okay but let's look closer.)

I also measured the impedances but did not plot them on this chart. The R is very much the same for all bands. The reactance (X) follows the SWR. These are not surprising.

I think these measurements show that the user does not need to pay much attention to where he/she mounts the pole. My metal-skin house is a worst-case scenario. However, very close to a large metal building may make it difficult for an auto-tuner to tune on 80m or 160m. 

Summary:

"Does it matter where you mount the pole?" This was the question at the heart of John Portune's antenna experiment, conducted on October 29, 2018. Using his existing 20 ft. flagpole setup, John positioned it close to his metal-skinned mobile home and further away to measure impedance and SWR.

Surprisingly, John's findings revealed that the presence of a nearby house or the flag itself had minimal impact on the antenna's performance, except for slight SWR changes on 80m near the house. The results indicate that the choice of mounting location isn't critical for most users.

However, for those with conductive metal siding on their homes, it's advisable to keep the antenna at least 18 inches away. If your home is made of non-conductive materials like stucco or wood, positioning the antenna within 15 feet and more than 18 inches from the house yields optimal results.

John's experiment offers valuable insights and confidence for getting back on the air. So, if you're looking to maximize your antenna's performance, stay tuned for more from the Greyline Performance Team.

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