AP Comparison for site survey

Answered Question
May 21st, 2009

Hi Guys,

Not sure if this is a repost, havent seen my old post go up yet..

I am due to do a site survey in the coming months, and just wondering is there any difference in doing the survey with a different AP that what is to be installed.When i say different, its not going to be a too different AP!

The customer is going with 1242's once the survey is complete, but I only have 1231's and 1130's to use for the survey.

I have looked at data sheets and havent seen too much difference between the 3 models, when using the standard aerials, which they will be using in the end.

Would this be acceptable?

Thanks in advance

Mike

Correct Answer by scottmac about 7 years 9 months ago

For a simple field measurement, it all boils down to three things; the antenna, the transmitter output, and the receiver's sensitivity and selectivity.

Of the three, the most likely to be variant is the receiver ... mostly because radio components may vary and be better (yay technology!) or worse (f'n beancounters making things being built cheaper).

Improved sensitivity without improving selectivity would be a Bad Thing (like having a wide-open amplifier ... noise gets amplified too). Selectivity is the ability of a receiver to discriminate the desired signal from the spectrum that also includes other transmitters and noise-type interferers.

As long as those three basic characteristics are substantially similar, the site survey findings will be substantially similar.

Even if the characteristics are not the same, if you know what they are, you can calculate the compensation, adjust the hardware, or add additional "fudge factor."

IMO, given the state of today's hardware, if the antenna(s) are the same (type and substantially similar Smith charts -- the radiation patterns), you'll get a valid survey.

Good Luck

Scott

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Scott Fella Thu, 05/21/2009 - 03:42

Well you already know that using the same ap the client will install is best practice, but since you don't have a 1242, I would probobly use the 1131 as long as you don't plan on installing any other antenna besides the standard dipole.

Review this doc and verify the max power for the channels you with to deploy, since some max power will vary between ap's.

Robert Rowland III Sun, 05/24/2009 - 05:28

I know nothing about their type of environment or possible AP quantity but have they thought about using the newer 1142 units instead ?

They can cost roughly the same as 1242 with some external antennas and are future feature enabled plus provide MIMO.

It seems the benefit of the 1200 series is the ability to use external antennas which wouldn't be omni. If you are going to use omnis and just do B/G why buy a 1242 and antennas - just get 1100s for half the price. If you are also going to use A skip the 1242 and go to something that supports N and also gives you the multiple antennas from MIMO.

Correct Answer
scottmac Mon, 05/25/2009 - 05:19

For a simple field measurement, it all boils down to three things; the antenna, the transmitter output, and the receiver's sensitivity and selectivity.

Of the three, the most likely to be variant is the receiver ... mostly because radio components may vary and be better (yay technology!) or worse (f'n beancounters making things being built cheaper).

Improved sensitivity without improving selectivity would be a Bad Thing (like having a wide-open amplifier ... noise gets amplified too). Selectivity is the ability of a receiver to discriminate the desired signal from the spectrum that also includes other transmitters and noise-type interferers.

As long as those three basic characteristics are substantially similar, the site survey findings will be substantially similar.

Even if the characteristics are not the same, if you know what they are, you can calculate the compensation, adjust the hardware, or add additional "fudge factor."

IMO, given the state of today's hardware, if the antenna(s) are the same (type and substantially similar Smith charts -- the radiation patterns), you'll get a valid survey.

Good Luck

Scott

miomalle Mon, 05/25/2009 - 23:32

Hi Guys,

Thanks for your help - in the end we have managed to get a 1242 to perform the survey.

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