[TowerTalk] Re: VHF antenna orientation

[Healy, Rus]

Jeff Singer wrote:

Hi all,

Here's an easy one. I am about to install a 10-ft vertical antenna for
2-meters. If I were to install it at the top of my tower, it would
interfere with the lowest rotating antenna only two feel above. My best
friend insists that it can be installed upside-down without any negative
consequences, while still giving us the height we desire. I say this is
preposterous. 

Can someone please state the facts? Thanks very much.

73 de Jeff K2KV
k2kv@netusa.net

_________________________________

NJ2L: This isn't as easy as you think. Electrically, your friend is
absolutely correct. However, most gain verticals are designed to be
mounted with the feed point at the bottom. We (Microwave Data Systems)
have had to sell replacement antennas to numerous customers who have
lost 900-MHz gain omnis to water incursion. (Some people don't learn
from this experience, either.) Many similar antennas have drain holes
near the feed point to allow water that leaks or condenses into the
antenna structure to leak out. In the upside-down mode, the failure mode
is obvious. However, if you're willing to build a little shield for the
antenna out of a bleach bottle or some such, and drill a drain hole at
the "top" of the antenna, you'll be fine. Go do it!

--73, Rus

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