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Old 10-30-2017, 2:37 PM
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Default Yagi Antenna Mounting Question

I recently purchased a 700 Mhz yagi for zeroing in on a local P25 simulcast site (scanner monitoring - no transmitting here), but I have a question on mounting. First see this picture:

It seems like the driven element is electrically connected to the antenna beam (this in itself is confusing to me - why?), so a few questions.

First, doesn't it create an issue to mount this on a grounded steel mast (the mast becomes an active part of the antenna?).

Also, even if the antenna was isolated electrically from the mast (lets say by a dozen wraps of electrical tape), doesn't the steel mast itself mess up the pattern for the yagi?

I've seen similar antennas mounted right on steel masts many times, so it would seem the answer to both questions is "no", but why is it "no" (assuming this is the case)?

In a past installation of an 800 Mhz antenna, the yagi was mounted to a short PVC mast so this wasn't an issue, but I'm now looking at putting this antenna on a steel mast, thus the questions.

Also, why isn't the driven element electrically isolated from the beam it is mounted to?

Any input is appreciated.

**I wasn't sure on which section to put this in, but this seemed like a good area to get solid answers, more so than the scanner area...and though I would expect that HAMs would have the answer I didn't want to put in the HAM area.
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Old 10-30-2017, 6:16 PM
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Type of mast will not matter. That's a "Folded Dipole" design. That it is a DC short is normal.
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