Ham radio antenna relocation

[dstevens]

Just curious. When you talk about the A pillar location are you referring to where I mounted mine or actually mounting the antenna to the pillar itself?

At the top.

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[Captain Skip]

Do you think where your mount has more metal so you get a little get a better ground plane?

Not really, there's not all that much metal on the mount. I think getting the coil and the part of the antenna that was alongside the fender and raising it above the hood helped. Now the whole top of the hood is available for the ground plane.

 

[4a4c55]

Average signal by antenna. Highest signal is best (ie least negative).

Great write up! I'm wondering how you made the signal strength measurements--particularly the polar radiation measurements.

 

[dstevens]

Great write up! I'm wondering how you made the signal strength measurements--particularly the polar radiation measurements.

Hand held spectrum analyzer. Marked circle. A lot of walking.

 

[SOTA]

Remember than 6 db is double or half the range.

Great data but double the signal strength does not necessarily equate to double the range.

On HF I can communicate half way around the world with 10 Watts and a dipole or with 1.5 kW and my multi element beam. The signal strengths are orders of magnitude different but once there is enough signal to noise it doesn’t matter.

Propagation, nulls and peaks in the direction of interest, near field vs far field etc etc all play a role so it’s not just a linear relationship.

 

[Captain Skip]

And with VHF/UHF radios simply moving 10 feet can make a difference.

 

[4a4c55]

Hand held spectrum analyzer. Marked circle. A lot of walking.

Does that work? Aren't you in the near-field effect radius of the antenna? (I know near-field exists, but that's about it. I'll go see if I can find the math to find the field radius given the antenna characteristics ...) But even if not, isn't the presence of your own body an issue?

 

[dstevens]

Yes, all of that is

Does that work? Aren't you in the near-field effect radius of the antenna? (I know near-field exists, but that's about it. I'll go see if I can find the math to find the field radius given the antenna characteristics ...) But even if not, isn't the presence of your own body an issue?

For 2m I believe I was outside the near field distance.

All I could do is keep the distance as constant as possible; the SA antenna was held up in the same way each time, and acknowledge that there were lots of factors I could not control.

But the signal varied nicely with distance from the Jeep and the signal also matched what I would have predicted with antenna location, so I felt that it was an attempt to gather some data on the antenna placement that was more accurate than just a yes/no for hitting a repeater.

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