Re: [smartBridges] Omni Antenna's

[Kevin Proctor]

Perhaps a tad bit of info on radiation patterns is in order here.  A unity gain antenna in free space will radiate a globe of radio energy.  To obtain gain, the radiation pattern must be "squished" into more of a toroid or donut pattern.  The higher the gain, the flatter the donut.

Since a 12 dbi omni is nearing the practical limit for gain from an omni, the donut has been squished pretty darn flat.  The shape of the pattern is more like a disk than a donut.  To get signal directed down to cover receivers close to the antenna, you either need a lower gain antenna or an antenna with down tilt built in.  If your antenna has no down tilt built in, you are shooting way over your receiver.  With the antenna at 45 meters above ground, (30 meters is sufficient in most cases) you will find you have good signal out around 2-8+ miles, but poor signal up close.  You are simply overshooting your receiver.

Either lower the antenna on the tower, replace the antenna with an omni with built in down tilt, or jack your receiving antenna up 20 meters or so.

Kevin

Rob Cleminson wrote:

I have just installed my new SB2510 AirPoint Pro Outdoor – I have it attached to a 12dbi Omni via 1 metre of LMR400 and it is hanging off the side of a 45metre Tower. For test purposes I have an AirNIC with a 2.2dbi stubby attached – from 0.5 miles – 1 mile I can only get a signal strength of 30% at ground level from my truck.

 

Should the signal strength be stronger at say 15 metres at the client end or should I still get a good signal at ground level?

 

I am having doubts that the Omni I am using is working correctly? And I do have perfect line of sight.

 

Any Advice?

 

Regards

 

Rob Cleminson

email: [EMAIL PROTECTED]

office:  01277-227130

fax:     01277-227068

mobile:07774-401200

web: http://www.remotebackups.co.uk

 

 

-- 
Kevin B. Proctor
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Electro-Comm Distributing Inc.
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