On 9/17/2013 9:10 PM, K8TB wrote:
The main disadvantage of a 4 bay omni is lthat you will pick up any
QRN located anywhere. But a 4 bay absolutely has gain on the horizon.
A 4 bay would have the proverbial 6 Db of gain, minus
splitter/feedline and connector losses. What the 4 bay does is squash
the donut flatter, and out. My day job depends on this (radio
broadcast engineer with 5 FM transmitter sites).
I plan to put up a 4 bay omni for six at my remote base site. Then
I switch over to the very quiet Innovative beam.
We all should look at more of these antennas, but, to obtain the full
3 Db gain per doubling, you need to space the bays a full wave length,
which is 20 feet. So the 4 bay would be 60 feet, bay 1 to bay 4. You
can get by with half-wave spacing, with less gain.
Tom Bosscher K8TB
I have never considered a 4-bay for 6, Tom...I know they're way too
big...but on 2-meters it is a reasonable structure.
As to QRN susceptibility, I believe the predominant component of power
line noise is vertically polarized, which gives the horizontal loop some
immunity. I recognize that, as John, AA5FC, pointed out, there is no
front-to-back or front-to-side rejection to help minimize QRN but the
loop stack at least allows one to have modest gain in all directions to
enhance the probability of actually hearing someone otherwise inaudible
in the nulls of even a smaller yagi.
I usually figure on 2.5db gain per doubling, which is probably a bit
conservative.
I am a retired radio/TV Chief Engineer with responsibility for an 8-bay
Class C FM station or two over the years. That was "back in the day"
when stations actually hired full-time engineers. :>)
73,
--
Jack, W6NF/VE4
Shelley, K7MKL/VE4
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