[grc] [Stubblefield] Mounting and spacing of 2 bay OMB MP 1 antennas?

[Michael D. Brown]

The size of mounting pole is partially dependant on how much unsupported
pipe we are talking about.
In most cases, we're talking about 1.5 to 2" schedule-40 galvanized pipe,
which has actual ODs of about 1.9 and 2.375" respectively.
 
In the middle of the FM band, 1 wavelength is almost exactly 10 feet.
We often specify 0.75 and 0.5 wave spacings.  They tend to work well, for
all the reasons you state, and more.  Gains for two bays are about 0.95 and
0.7 respectively.  In most cases, 0.75 to 0.78 spacing has the best
gain-per-foot.
 
 
mb
 

Michael D. Brown
Brown Broadcast Services, Inc.
3740 SW Comus St. ● Portland OR 97219-7418 USA   
 <mailto:mike at brownbroadcast.com> mike at brownbroadcast.com  ●
<http://www.brownbroadcast.com/> www.brownbroadcast.com
offc 503-245-6065 ● cell 503-703-3202 ● fax 503-245-5773 


 

 


  _____  

From: Stubblefield [mailto:stubblefield-bounces at lists.prometheusradio.org]
On Behalf Of Danny
Sent: Thursday, August 11, 2016 3:19 PM
To: grc at maillist.peak.org; stubblefield at lists.prometheusradio.org
Subject: [Stubblefield] Mounting and spacing of 2 bay OMB MP 1 antennas?



We’re working with a property owner that is very concerned about the visual
impact of us putting a 2 bay OMB MP 1 antenna system on their roof cupola.
Wind and icing aren’t serious concerns, so how skinny a mounting pole can we
use and how far apart do we need to space the bays and how far above the
cupola roof? The latter is stone tiles with metal trim.

 

I read elsewhere that as the spacing changes, so will the gain of the
antenna system. That running it full wave, we will get higher gain (unity,
or close to it) , but that most of that energy is going "up" rather than
horizontally. And if we decrease the antenna spacing, the pattern "squashes"
towards the horizon, resulting in less energy going straight up toward space
and more toward the horizon. Which is more desirable, obviously. The down
side is the efficiency decreases, so you need more transmitter power to make
your assigned ERP. Does this make sense?

 

Lastly, where does the power splitter go?

 

Much thanks!

Danny

WSPJ-LP Syracuse NY

 

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