I've been disconnected from the Wi-Fi world for a while. I am looking for an access point model to buy off-the-shelf with the following requirements:
- External antennas with SMA easy to connect to a RF conducted test environment.
- Configurable TX output power
- Configurable Wi-Fi channel (2.4 GHz, no need to test on 5 GHz)
- Configurable PHY data rate (not really important though)
Thanks a lot and kind regards,
An AP with a native SMA connector will be almost impossible to find. One with RP (reverse polarity)-SMA will be much easier. Many Cisco AP's use RP-TNC - both connectors can be connected through conversion adapters. (usually available at Frys Electronics, or try Pasternack).
BTW, good quality BNC connectors/adapters are more than adequate for 2.4 GHz.
You choice of Coax cable will be one of your limiting factors - double shielded is the best.
Just about any older /b/g AP will let you adjust the power levels - albeit rather coarsely. Ham Radio Swap Meets are a good source. Great a/b/g Cisco 1130 AP's can be had for $5-$10. Just be sure to get the correct voltage/current/polarity power supply for it.
If you can find a decent Step Attennuator that works in 2.4 GHz you may be able to make-up, somewhat, for not having the finest RF power control you'd like.
Remember, that for all intents and purposes, AP and client manufacturers lie/exaggerate about the radio's performance. Power levels may be off up to plus or minus 2 dB. It's very unlikely that power levels will be exactly flat across the channels, and "secret-sauce" ingredients may affect any testing you do. The most honest manufacturer in my experience, when it comes to power output, is Cisco.
Don't forget that real AP's will need an external Router to supply IP addresses, etc. - as opposed to a home Wi-Fi Router.
I was lucky. I had several $50k+ Anritsu WLAN test sets to play with, and multiple RF enclosures when I was testing a/b/g/n/ac radios. You can still do a lot if you can find, or make, a quiet RF test space.
Also get yourself some kind of tool that shows RF levels by channel - the more sensitive the better. Even a phone App or PC utility can come in useful.
Thanks a lot for the detailed response Howard, appreciated it.
I got my hands on a Cisco AP1262N that was getting dust in a cupboard and I am in the process of getting a channalyzer tool (unless I find a suitable alternative) for RF characterization. The idea is to setup a small RF conducted environment and play a bit with a packet generator (iPerf will do). I am not sure though which RF combiner should I get (only interested on 2.4 GHz), and I am wondering how multiple spatial streams will perform on a conducted environment.
I have not tested MIMO (multi-stream) transmissions over conducted paths, but have tested them over radiated links. The R&S and/or Anritsu LAB gear necessary for multi-stream testing is well over $100k. But those test many more parameters than you were probably planning to test. I'm just guessing, but phase stability might turn out to be an issue depending on how sophisticated your tests get.
However, I have extensively tested many AP's and client radios that had (spatial) diversity antennas in radiated tests. The splitter/combiner that I used at my last job for these was made by Trilithic. It was, I think, a model xwpd-528-6-sma-r. It worked beautifully up into the 5 GHz band. New, it was several hundred dollars. Hopefully you can find something cheaper. Maybe Mini-Circuits has something.
Cables AND connectors are going to be VERY important. I used RG-142 cables (double shielded, etc) with professionally installed BNC and SMA connectors without any problems. Be sure to correctly and consistently tighten any RF connectors.
You will need some very good attenuators that work up to at least 3 GHz - you don't want to blow any of your radios (or Channalyzer) ! Even at the lowest AP power settings you'll need quite a few dB attenuation. The Anritsu gear I used had all those built-in, for both input and output.
I suggest you have the complete Cisco configuration manual for the 1262. The GUI controls may be a little lacking, and you may have to use the CLI interface.
Make a backup copy of its firmware before you start. TFTP works well for backup/restores and you can install/enable it on Windows systems.
Good luck. Let me know how it goes.