Test setup

[Flavorflav]

I'm trying to build a test setup and the router I have has two antennas - as, in fact, do all of the other routers I have examined closely. Am I right in thinking that we are going to leave one of the antenna terminals on the router alone, and hook the testing apparatus up to the other one?

[knightmoves]

Is your router single or dual band? If it's dual band, it will have one or more antenna for 2.4 GHz and one or more for 5 GHz. Make sure you use the right one!

Lots of modern routers have fancy features like beamforming and adaptive power levels. You don't want any of that stuff. If your router has that stuff, make sure you can turn it off.

But you certainly don't want any of the other antennas present. Having them disconnected might be OK. Connecting them to a 50 ohm terminator might be better.

[Flavorflav]

I got the one that was suggested at the Summer Clinic, the ASUS RT-N12. I have looked at all the documentation I could find and it doesn't actually say if it is dual-band, it just says "Two detachable 5dBi antennas for more powerful and wider coverage." I'm guessing that if it were dual-band it would say so. If it is single band, it should not matter which one I connect to the student antenna, correct? And if it were dual-band, don't you think there would be some indication of which antenna is which?

[knightmoves]

I got the one that was suggested at the Summer Clinic, the ASUS RT-N12. I have looked at all the documentation I could find and it doesn't actually say if it is dual-band, it just says "Two detachable 5dBi antennas for more powerful and wider coverage." I'm guessing that if it were dual-band it would say so. If it is single band, it should not matter which one I connect to the student antenna, correct? And if it were dual-band, don't you think there would be some indication of which antenna is which?

It's single band, from a quick google.

My first thought would be that you disconnect both antennas, terminate one, and connect the other to the test apparatus, and it doesn't matter which. Termination might not be necessary - just leaving the other antenna disconnected might be OK.

[knightmoves]

I have a new question about the test setup. There's a square 30cm backplane made out of wood or something like that, with a female SMA connector in the middle. The antenna is supported by the SMA connector (so there's a limit on the weight you're allowed - shoudn't the 300g in rule 3f be an actual rule, rather than a recommendation.

The rules don't say how the SMA connector is mounted to the backplane, or how far it protrudes. Looking at images of SMA connectors and bulkhead jacks, it seems as though different ES could reasonably put together a test setup with a different amount of SMA screw thread protruding from the wood, which means the antenna will have to sit at a different distance from the wood.

I'm assuming we want to have some feet that touch the wood backplane to give the antenna stability, but this uncertainty means that the feet need variable length, which is "interesting" for the "always fit in a 15cm cube" rule.

There don't even seem to be any guarantees that the connector is mounted securely to the wood and emerges perpendicularly from it.

Am I over-thinking this?

[knightmoves]

Hey, Flavorflav:

It looks like I'm going to try and build a test setup too. I found an old WiFi router in my house that wasn't being used. It didn't have external antennas, but does have what looks like a U.FL connector on the circuit board. So I've bought a little U.FL to SMA cable, and hopefully that will work.

I suppose I'm going to have to cut the traces on the circuit board to disable the printed antennas - hopefully just scoring through the traces at the edge by the antennas will work well enough. I suppose I could try just wrapping them in grounded aluminum foil as a sort of Faraday cage instead.

The SMA connector is a standard-looking female bulkhead connector, but it looks like it's designed to be mounted on a thin metal / plastic box rather than the 1/4" (yeah, the rules say ~0.5cm, but if I buy a sheet of MDF or whatever from the hardware store, it'll be 1/4"), and it's not obvious that mounting it in a 1.4" board will leave enough of the connector poking though the hole for a good connection. So maybe I'll have to put a little 3/4" recessed hole on the back a couple of mm deep to give me a bit more connector available.

So far, my plan looks like:

1. Power up WiFi router and check signal level with my phone
2. Unplug, cover antennas in grounded foil, power up and hope to not see a WiFi signal
3. If I still see a signal, start cutting traces.
4. Plug in U.FL to SMA and reference monopole antenna, check signal level again.

And if all that works, I have a viable setup to start doing something with.

Advice and criticism welcome.

[Jomacteacher]

https://www.soinc.org/sites/default/fil ... 171002.pdf

This gives directions for building it, but I am having a hard time getting the SMA male to male cable. There is one listed on Amazon, but it won't get here until November. Any ideas where to get the cable? Can it be swapped out with a normal coax cable if the connectors have adaptors? We know nothing so simple language please. We're learning.

[andrewwski]

Do you mean the RP-SMA male to SMA male cable? If so, you could get an RP-SMA male to SMA female connector + an SMA male to SMA male cable instead. For example:

https://www.amazon.com/DHT-Electronics- ... 025&sr=8-3

https://www.amazon.com/WayinTop-Antenna ... 216&sr=8-5

Plenty of options available on Amazon Prime if you go this route.

[knightmoves]

What are people getting for the reference signal level for the 3.1cm reference paperclip at 3m distance? Mine comes in at about -60 dBm.

[szelazny]

I've read over the instructions and it' not clear to me whether or not the router should be mounted to the back of backplane or just sit on the floor. The picture on the bottom of page four sort of makes it look like the router is on the floor.