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120° vs 90° vs Omni

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120° vs 90° vs Omni

In order to get coverage over 360°, is it better to use 3 120°, 4 90° or an omni? I need to get out 1 mile and am thinking rocket 5g.

K5DLQ's picture
MUCH, MUCH, MUCH better to

MUCH, MUCH, MUCH better to use use 3 120° sectors with Rockets on 3 different frequencies.

K6AH's picture
1 mile isn't far...

if it were me, I'd use the Omni.  1 mile just isn't far enough to justify the expense of sectors which could cost 3 times as much.  If the requirement was 5 or 10 miles I would agree completely with my esteemed colleague.


K5DLQ's picture
ah yes.  I missed that detail

ah yes.  I missed that detail of only 1 mile.

Thanks for that info.

Thanks for that info.
How far out do you think an omni would be good for?

couple miles

depends on what your clients are using..   I've had good luck for a couple of miles with both ends using a gain vertical.

if your client is using a dish, probably double that distance.

Richard    ke7xo

K5DLQ's picture
I have omni's that are

I have omni's that are linking 25 miles.  one is at 450', one at 200', one at 200'

K7OPA's picture
When you say linking at 25

When you say linking at 25 miles can you tell us at what bandwidth and truput?


K5DLQ's picture

channel -2

TxMbs ranges between 3Mbs and 5Mbs

N0KMO's picture


If you open the bandwidth to 10 MHz what does that do to the mileage?



K5DLQ's picture
As bandwidth increases,

As bandwidth increases, distance normally decreases (standard RF stuff).

ke6bxt's picture
120° vs 90° vs Omni

Q: When does 120 + 120 + 120 not = 360 (or when does (90 + 90 + 90 + 90 not = 360)?
A: When you are looking at coverage area and localizing traffic.

Look at the radiating pattern for the sectors here:

With four 90 degree sectors you have kind of a four leaf clover radiating pattern.  With three 120 degree sectors you have more of a three leaf clover radiating pattern.  You need to take into account where your nulls will fall and try to have them where your users are not located.

Also with the three or four sector antennas it is much more important to have RF shielding (sometimes called RF armor) on each antenna to keep the RF from one antenna from getting into and de-sensing the other two or three antennas at the same site.

So, you might ask, "With the additional cost of three (or four) antennas and radios (and cat5e STP, and POEs...) why go with sectors rather than one omni?"
The answer is to isolate local traffic. If most of the users on the North side of your site talk primarily with other users on the North side of your site, and similarly for users on the West, South, and East sides of your site, then the traffic will go in one antenna and come out the same antenna with no impact to users on the other two or three served areas.
And, for the traffic that comes in on one antenna and goes out on another antenna, you can use frequency diversity so that traffic can be received and transmitted simultaneously.

One more thing to consider... When mounting sector antennas, they are mounted facing away from the tower.  When mounting an omni antenna, your radiating pattern is going to be affected by the tower. Depending on the spacing from the tower leg the radiating pattern can be changed dramatically from the perfect circle we think of an omni antenna having.

One final point is down tilt.  This document shows the beam width and down tilt of the Ubiquiti omni antennas.
If your node is significantly higher than than your users you may be shooting over the heads of your users when using an omni.  With sector antennas it is much easier to adjust the amount of downtilt/uptilt to cover the desired target area.


wa2ise's picture
I'm lucky if I can get more

I'm lucky if I can get more than a mile in the tree infested region of NNJ I live in... sad

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