connectorized SM to non connectorized ap

Can you use a connectorized 900 sm with a yagi antenna to connect to an integrated 900 ap?

also, will putiing an omni directional antenna on an ap give you 360 degrees?

:slight_smile: We use a cushcraft 10 element antenna for our SM. You have to change the mounting bracket to Horizontal Polarization. Cuchcraft makes a 6, 10, 13 element yagi’s.

The 6 is equal to an integrated SM Panel as far as gain and beam width. The 10 Element is what we use on a regular basis.

PC906N (10.65dbi gain)
PC8910N (13.15dbi gain)
PC9013N (15.1dbi gain)

When we do site surveys of our customers to see if we have service at there location, we normally use the 10 element from the ground to see our link test.

The integrated and connectorized are functionally the same. You can mix and match 900 AP’s and SM’s with no problems.

As mentioned, if you use connectorized AP’s and SM’s make sure you orient the antennas horizontally.

I use the 10 and 13 element yagis as well with good results.

be careful that you don’t use more gain than you need, or lower the output power of the radio to what is required for a good link (10db margin).

Jerry Richardson wrote:

be careful that you don't use more gain than you need, or lower the output power of the radio to what is required for a good link (10db margin).

Jerry, can you explain this a little bit more if you have time? :) We have a customer who is using 900 and is only .35 miles from the tower. I lowered his power from 28 to somewhere around 22. His power level is around the 50 dbm range! I could prob. lower it some more.


The specs of the integrated 900SM:

* Carrier to Interference ratio (C/I) ~3dB @ 3 Mbps, ~10dB @ 6 Mbps at -70dBm
* Nominal Receiver Sensitivity (dbm typical) -90 dB
* Antenna Gain (dB) 12.5 dB
* EIRP (dB) 36 dB
* Equivalent Isotropic Radiated Power (EIRP) 4 W

All you need is -70dB to establish a good link.

Anything over 60dB is excessive energy on the RF interface. While this might be fine for the SM, it desensitizes the RF interface on the AP from being able to pick up weaker signals (read that SM’s without LOS, or further away). With a few SM’s you will not notice it as much, but as you add subscribers you will start to compound the problem if you don’t balance your RF levels. Less is more.

Another way to look at it is imagine looking into the beam of a flashlight 10’ away from you, and trying to see the beam of another flashlight 1/4 mile behind and just to the side the first one. All you can see is the one 10 feet away. Turn down the intensity of the closer flashlight and you can start to see the flashlight behind it. Ideally you would want to turn down the intensity of the closer flashlight until it’s intensity is equal to the one that’s further away.

On the other hand, anything under -80dB is cutting into your 10dB margin (the radios nominal receiver sensitivity is -90dB). At these low levels you are really prone to interference.

We try to keep levels between -65 and -75 (but this is easier said than done).

Hope this helps.

Thanks! Much appreciated.

So basically IMO, the customers who have weak signals (80dbm and higher) should suspect problems. We should have never installed them in the first place. Or put up that remote AP I have been wanting to do for a few months now.

Our policy, if they don’t get 100% up and down on the link test. we don’t install it. We shoot for atleast a powerlevel 68 minumum

You can have happy customers with 50% efficiency up. 90% down is really the critical number.

Before adding a remote AP, if you have a customer that is down in the -80s’, try a connectorized SM with a 13dBi Yagi. We get good links out to 15+ miles with that combination. I could easily get out to 20 miles as well.

Don’t worry about too much energy, you can always turn the radio power down.