Tomato Missing Channels 1-4

18 posts / 0 new
Last post
twt
twt's picture
Tomato Missing Channels 1-4

I have a WNR3500L I bought to replace an aging WRT54GL. I've been using the Netgear stock firmware since last fall with no serious problems. However today I had some network trouble and I was more annoyed than usual at my lack of local DNS and other niceties so I bit the bullet and installed Tomato Firmware v1.28.7475 MIPSR2-Toastman-RT K26 Std. (I used the recommended DD-WRT image for the first flash.)

With Tomato I have had some really strange trouble getting QOS to work right (our two VoIP ATAs are the most important traffic for family harmony). I also have noticed the default wireless signal is MUCH worse than the stock signal. It looks like if I crank the Advanced --> Wireless transmit power up to about 175 I get close to the original signal level. From my reading here and elsewhere it sounds like I shouldn't need to set the power that high.

But the most noticeable weirdness is that when I look at the Basic --> Network settings, the channel numbers start at 5 so I cannot choose or scan channels 1-4. WHY? 

I did the 30-30-30 reset before and after the firmware upgrades, and I have backed up the config and reflashed and reset the nvram then restored the config... no change.

Should I try different firmware next?

twt
twt's picture
a small update -- I believe I

a small update -- I believe I have QOS working as expected now; I set the bandwidth control for VOIP to "none" and that fixed the latency and dropout problems. However I have NOT figured out why the wireless signal is so weak compared to the stock firmware, or why channels 1-4 are missing.

Mercury Joe
Mercury Joe's picture
Under Advanced --> Wireless,

Under Advanced --> Wireless, what is your country setting?

Different countries only allow some channels. I have access to channels 1-11 and I am set to United States. Some countries allow access up to channel 13 I believe.

As for cranking up the power, Toastman has posted a chart that shows above 60 or so mw, you get no increase in signal strength. All you are doing is overheating your equipment at 175mw

twt
twt's picture
I did think of that, and I am

I did think of that, and I am set for United States, too. I tried United States Minor Outlying Islands and it didn't help.

As for the power, I have read in other places that the "mW" indication is apparently not ACTUAL "mW" from the transmitter chip and the transmitter isn't going to overheat anyway. I don't know who to trust on this one. HOWEVER I know the "default" setting in Tomato (12 or whatever it was) only reaches a tiny fraction of the distance around the house and yard that the stock firmware did. I have tried some different settings and even though the signal is not as strong as before I can get acceptable results with numbers less than 100...

I don't know how or why but it sounds like something is screwy with this image so maybe I need to 30-30-30 reset, flash DD-WRT, wave a dead chicken, and re-flash Toastman, or Tomato Jellyman or whatever it takes.

twt
twt's picture
I found the answer! (Well,

I found the answer! (Well, about the channels, anyway.)

Go to Basic --> Network

Wireless section: the Channel Width setting was 40Mhz (instead of 20). When the channel width is 20, you get all the channels starting at 1. When it is set to 40, they start at 5.

I don't know exactly what the "width" means -- my new Panasonic blu-ray player's wireless settings suggested it could use 40Mhz width and maybe that's why I changed it without thinking. Maybe the 40Mhz width doesn't travel as well so I will try it at 20Mhz and see what happens.

To recap: I installed a bigger version of DD-WRT then flashed Tomato again, this time using Tomato Firmware v1.28.7475 MIPSR2-Toastman-RT K26 USB Ext. We will see how it works. I restored my config file from the "smaller" version of Tomato to save having to reenter my DNS and QOS settings and I can wipe everything and try again if need be.

Toastman
Toastman's picture
Simply put, if you chose

Simply put, if you chose 40MHz setting and were on channel 1, then the signal would transmit outside the wifi band! Channel 5 is the lowest channel that permits 40MHz. You can also change sideband lower/upper which will change things somewhat, the channels displayed are simply the ones that are safe / permitted to use.

http://www.dd-wrt.com/wiki/index.php/Wireless-N_Configuration

Singapore is a good country to choose when doing experiments because it allows channels 1-13 at full power.

Turn off all unnecessary options in Advanced/Wireless - especially Interference Mitigation, which is responsible for a lot of connection and signal strength problems. Experiment with it on (WLAN AUTO) and off to see any difference.

You can't overheat anything using the txpower settings, don't worry about it. The maximum setting on RT-N16 with Tomato is around 60. Above that simply has no effect on strength. I believe the E series routers are the same (the E3000 is).

A good tool to see what these settings are doing is InSSider - it's free and very very useful, it displays channel graphs and also measures signal strength using your wireless card.

This will save you a lot of hassle restoring settings between builds and routers:

http://www.linksysinfo.org/forums/showpost.php?p=362345&postcount=221

There have been many posts on here and on Linksysinfo.org related to these topics. Reading through them would be a good idea.

As far as I know, all current versions of Tomato use the same base (Tomato-RT) by Teddy Bear, and the wireless driver version i.e. the behavior is the same on all of them.

How well does it work? Well, I can see and connect to both RT-N16 and E3000 in my apartment, at similar strengths, -72dBm, from around 30-40 meters away through several concrete walls. That's approximately the same strength as the WRT54GL running at a setting of 150. That is much bigger than the average house. You should be able to achieve something similar.

There are a lot of useful links here:

http://www.linksysinfo.org/forums/showthread.php?t=63486

twt
twt's picture
Thank you, Toastman! I really

Thank you, Toastman! I really appreciate it.

I found the wireless penetration to be poor at the 40Mhz and back closer to "normal" at 20Mhz so I am going to avoid that until I understand it better. Thank you for the resources for testing.

I only alluded to it above, but my bigger concern is the QOS has been terrible -- just about anything I do destroys the latency. I got the VoIP "fixed" by setting its class to "NONE." If I had ANYTHING else set for it, when the router was under heavier load the VoIP latency would frequently go up to (what sounded like) 1000-1500ms -- really terrible delay for phone conversations.

So far I have been unable to find any acceptable setting for Media that works while downloading movies to my media player...

I just noticed the router's home page says the CPU is running at 133Mhz. Since this is a Netgear WNR3500L/U/v2 I presume it should be running much faster, and that could explain the terrible latency. I will try adjusting the CPU Frequency and rebooting...

twt
twt's picture
@kt_haddock ... I tried a few

@kt_haddock ... I tried a few things and channels 1-4 never appeared when I was on 40Mhz, HOWEVER in my neighborhood there are fewer folks above ch 9, so it was not a problem. For now I am going to ignore the 40Mhz width; maybe my blu-ray player is the only device that knows how to do the double-width signals anyway, and if its range is diminished using it I will just avoid it for now.

@Toastman I am using a great free tool on my Android cell phone called WiFi Analyzer that displays a graph similar to the screenshots for the inSSIDer tool. It has the "overlapping humps" chart plus several different ways to read absolute signal strengths, and it rates various channels to help you choose the best one. It just told me channel 11 is the best, followed by channel 1.

Using Wifi Analyzer just now I discovered, for example, that if my blu-ray player were about four inches higher (behind the TV?) the signal would be 20db better. Maybe I can find another spot in the room that works reliably. Ultimately I will run an Ethernet cable and stop using wireless in that room; I've just been lazy.

twt
twt's picture
Another update -- the QOS

Another update -- the QOS seems to be running properly now that I have the CPU set at 453 Mhz instead of 133 Mhz (the default setting under Tomato). My understanding is that the "453,226" setting is the "normal" speed for this hardware.

twt
twt's picture
So far everything is working

So far everything is working very well, and I read the article about Wireless N to figure out how to use 40Mhz bandwidth. I set the channel, bandwidth and security properly and was able to use it. But I probably won't continue. To summarize:

It's NORMAL to only see channels 5-11 when you have the channel width at 40Mhz.

However, unless you have a good reason you probably want to stick with 20Mhz as many devices can't use it AND the additional signal will stomp on more of your neighbors' access points.

OH and for whatever reason, on my hardware I needed to manually set the CPU frequency to 453,226 in order for the WNR3500L to operate at normal speed. It couldn't handle QOS rules at a quarter speed.

Thanks for all the help!

Toastman
Toastman's picture
I think you're there now.

I think you're there now. Just one thing to remember is that WiFi Analyzer can only identify other data transmissions, so it won't be able to identify other interference. Channel 11 is quite subject to interference from Microwave cookers, which tend to hover around at the top of the band.

twt
twt's picture
@Toastman Thanks for the tip!

@Toastman Thanks for the tip!

Strangely enough, in the same way I discovered the signal varied greatly from inch to inch within the room, it also turns out a neighbor across the street has TWO access points on ch. 11. His signals don't make it to the room with the media player, but they do come through to my office in the garage. SO even though the s/n ratio was acceptable I picked yet another channel to avoid trouble.

For now!

(All this underscores that I really ought to run Ethernet to the fixed items instead of depending on wireless! A nearer neighbor could install a media player and the throughput to mine could go way down again.)

Mercury Joe
Mercury Joe's picture
Sorry to have missed the

Sorry to have missed the discussion, I was on vacation. Great info.

The normal CPU frequency for a WNR3500l is 480MHZ. This is listed on the data sheet at the product support web page. Look under "Learn More" and it is on the PDF.

twt
twt's picture
@Mercury Joe: Thanks for the

@Mercury Joe: Thanks for the information. I just bumped it up to 480,240 and rebooted. Of course it seems to be running fine.

I am curious that this router, even at 480 Mhz, takes a good minute and half to reboot. I assume that's normal... I believe the stock firmware took a similar amount of time. My main basis of comparison is my WRT54Gs -- they take about half a minute to boot. I have some D-Links that boot even faster.

No big deal, though, since I almost never reboot it (not even a scheduled reboot).

Mercury Joe
Mercury Joe's picture
The WRT54g typically used a 2

The WRT54g typically used a 2.4 linux kernel and it was stripped of features. The boot was very simple process.

TomatoUSB for a WNR3500l uses a 2.6 kernel, which is much more complex in and of itself. You also have to initialize additional things like the USB ports and the IPv6 stacks that are not compiled into the WRT firmware.

Toastman
Toastman's picture
Yes, this is curious. I

Yes, this is curious. I noticed some of people who flash the E3000 are having problems because after 2 minutes or so they assume the flash has failed and abort the process - then of course they often find their router is "bricked". For some reason the E3000 just takes a very long time to flash and reboot even compared to the RT-N16 - despite having similar hardware. I have one here and I have known it take 3 minutes+

So different routers do behave differently.

Mercury Joe
Mercury Joe's picture
Toastman, I do belive he was

Toastman, I do belive he was talking about a reboot cyle, not a flash.

Could you enlighten us as to why the TomatoUSB takes so long on the faster newer routers than Tomato on the older routers.

Toastman
Toastman's picture
True, but I was counting the

True, but I was counting the reboot cycle into the flash time. Today's builds are bigger so longer times are understandable. But both flash and reboot appears to be slower on the E3000 than on the RT-N16. I have no idea why this should be.