HyperWRT and "rx antenna" & "tx antanna" settings


Anything from totally mess everything up, to nothing... depending.

Yes, but only one antenna at a time, and only transmit or receive at one time... and on which antenna, again depends.

If you starting to get the idea this *all* depends... It *does!* (And eventually, after all of these comments, I'll try to explain some of it.)



Probably not though. Think about that for a minute. If you crank it all the way up, that's 255 mW of power, or 1/4 of a Watt. If that chip is only 25% efficient, that means it is dissipating 3/4 of a Watt.

So reduce the power all the way down to the default 28 mW, and if that chip is still only 25% efficient, the chip will be using

112 mW of power, 28 wW will be RF output, and 84 mW will be heat. So you've changed the heat dissipation from .750 W to .084 W, or a reduction of 2/3rds of a Watt. 2/3rds of a Watt isn't what's heating up the box... and if you reduce the standard 28 mW, you obviously won't get anything close to any 2/3rds of a Watt reduction.

I have a wrt54g that has a single antenna, and of course both tx and rx are locked to that one (if you do that, use the antenna socket nearest the power socket, as it has a much shorter connection inside the box).

As I'll explain down a ways, you might be better off moving the

1st Floor units to the 2nd floor, and the 3rd Floor units to the 5th floor. Hopefully (you'll have to test and see), each unit can cover one floor above and one floor below. The question is, will it go through the roof, and do you need that unit at all.

Since you are going up and down, horizontal polarization might be better, depending... if there is any location where you can point the two ends of the antenna toward areas that will never be used by a client, it will be better. That is particularly true because you are using one unit in the center of each floor.

An example that does not fit your situation, but which might illustrate the point, would be one large rectangular room with two AP's. If they are located about 1/3rd of the way into the room from each end, perhaps vertical polarization would be best. I they are at the ends of the room, horizontal polarization would be better (especially if a reflector could be added to bounce what would go out the wall back into the room).

Think about the "donut" shaped pattern around an antenna, and see if that makes sense. If it doesn't (for example if the idea of a "donut" shaped pattern doesn't ring a bell), just say so and I'll let Jeff Liebermann try explaining it! :-)

Wow! You've got a *lot* of stuff that this depends on!

First off, lets understand what those antennas are doing and how they are switched, so that you can get a better idea of the effect of any given configuration.

Either the transmitter or the receiver, connects to one or the other of the antennas. When a receiver is connected, it will switch antennas at regular intervals (whether it is receiving a signal or not), looking for the best signal. Hence if you have two very different antennas, it will eventually pick the best one for any given signal.

But the transmit *always* starts with the antenna last used to receive. That assumes it will also be the best signal, but it just ain't necessarily so! Lets say you have two highly directional antennas, one pointed north and one pointed south. If a client to the south transmits, it may take a bit, but the receiver will eventually pick the south antenna and will see the signal. At that point, no signal from the north will be received until at least the interval it takes to test the other antenna, so a second client to the north is going to wait much longer to connect than would another client to the south.

Worse though, is if the receiver is seeing a steady signal from south (somebody doing a big file transfer for example), and a packet of data needs to be sent to a north client. The transmitter will *always* use the last antenna used for receive, which in this case is *always* going to be the south antenna. The north client will *never* see it, until it happens to transmit something itself and cause the north antenna to be switched on for receive.

Which is to say, except for point-to-point links, you may want only antennas that are very nearly the same. If you have only one client, and that client roams widely, then the increase coverage would be fine, and there would be little effect from switching disparate antennas. But if this is an office building or an hotel, and there might be many users connected over this wide coverage, disparate antennas being switched might cause them significant annoyance.

That applies to polarization in ideal situations, but less so in real situations. In your case, the amount of multipath from various reflecting surfaces is almost certain to cause polarization of received signals to be all over the map.

Specifically, since you are getting good coverage, you obviously have a workable configuration! The only thing I'd suggest is checking to see if that rooftop unit really needs to be on the roof. On the roof it probably only provides coverage for one floor below. But if you put it one the top floor, will it then cover the roof, the top floor, and the next one down? If so, you get three floors with one unit, and you might lessen the amount of off premise exposure too. Of course, if the roof is metal, that won't work...

Reply to
Floyd L. Davidson
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For a Linksys wrt54g with stock/factory antenna's, what would messing with these settings do for me?

What situation(s) would setting, say, the left for transmit and the right to receive do for me?

If settings were kept in default "auto" mode for both antenna's, I "assume" that both antenna's do tx/rx correct? If so, would orientating one antenna horizontally and the other vertically help get more area, assuming the above puts the unit in some sort of "diversity" mode?

Would dedicating them to a single function help anything for me using stock antenna's? I do have the 7dBi Linksys antenna's that I am going to put on the wrt54g after my testing is done so I can reduce the power on my wrt54g so, that might help keep the heat down a little.

Anyone using anything other than "auto" ? If so, for what kind of application? More curiosity then anything else.

Environment: I have a 5 story brick building with six unit's/flat's/condo's per floor and have an elevator shaft smack dab in the middle of building. So, what I have so far is:

- 1st floor elevator left side of shaft a wap55ag (ch6) and on the left side a wrt54g (ch1)( both external to the elevator shaft )

- 3rd floor hall a wre54g repeater (ch6) on same side of elevator shaft as wrt54g ( externally of course ) doing WDS with wrt54g

- 6th floor ( roofdeck) a wap55ag (ch11)

wrt54g ver3 running Firmware Version: v3.03.6 - HyperWRT 2.1b1 - not using wan port/router wap55ag ver2 running Firmware Version: 1.1 - factory

Now, scenario above "seems" to get decent coverage all over the building with this setup so far. I have been playing around with the settings on the wrt54g though always trying to get the best coverage I can get by adjusting antenna orientation, etc, AP placement, etc. As of now, I have all of the AP antenna's orientation vertically. Would ( for the wrt54g ) setting one of the antenna's vertical and the other horizontal help me? I have done walk tests with NetStumbler and haven't seen any huge gains with different antenna orientation but, thought I would double check myself with ya'll on what ya'll have seen/experienced. Does my thinking make sense above or am I over/under thinking something?



Reply to
Scott Nelson

-->Uh, no that's OK. Makes sense to me. ;-)

-->This does make more sense to me now. Never occured to try just one Antenna and not use the other one.

-->I would love to move the AP's but where they are is, by the fact of, the

1st floor AP's are there in my place and the 6th floor AP ( roofdeck) is there becuase I found an empty conduit to the roof for a network connection and I needed coverage for the roofdeck anyway. Unfortunatly I have no way to get CAT5 to the 2nd through the 5th floor. I did give it considerable thought though..... Even with PoE I don't have a lot of choice. I did consider "powerline" networking to a wrt54g per floor but, powerline doesn't seem to be getting good reviews.

Thanks a bunch for replying. I really appreciate it! I have some new ideas to try now. :-)


Reply to
Scott Nelson - Wash DC

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