DD-WRT vs Alchemy (WRT54GS clients miles to AP)

Discussion in 'DD-WRT Firmware' started by tlj, Jun 7, 2005.

  1. tlj

    tlj Network Guru Member

    I am in the process of getting ready to install 1,000 Linksys WRT54GS wireless routers as clients. I was testing the Sveasoft Alchemy firmware but found I could not establish a connection to my mountian tower access point. I re-flashed to DD-WRT firmware and I can now connect.

    So, as a note to anybody trying to bring up a WRT54GS in client mode - The Sveasoft Alchemy firmware does not make a connection to my AP miles away - but the DD-WRT firmware works great.

    I tested this on a dozen Linksys WRT54GS routers at every possible power level using the RooTenna 14 & 19 db antennas. Bottom line - at this time the DD-WRT firmware works as a client if your are miles away from the AP. The Sveasoft Alchemy does not connect to my AP which is miles away.
  2. windsurfer

    windsurfer Network Guru Member

    I spent a couple of months testing different versions of software over a 3/4 of a mile link and DD-WRT was the only one that would connect correctly in client mode using a WRT54G Version 3.

    Some of the others would allow the radio to connect but it would not route to the Lan ports correctly. Others seemed to route correctly but the radio would not connect.

    DD-WRT is the best for my application.

  3. tlj

    tlj Network Guru Member

    Update on distance - I am getting over 10 miles with DD-WRT

    Just wanted to post an update

    I have many Linksys WRT54GS (DD-WRT V22) clients connected to 19 db rootennas well over 10 miles from my AP.
  4. xrattiracer

    xrattiracer Network Guru Member

    thats some very interesting information. I work at a wisp and have often wondered how well a wrt would work as a customer premeses equipment. as it is we use a rather expensive commercial solutuion thats good for a max of about 12 miles (using 24 db parabolic antennas, 200mw power).
    one of the things i am concerned with is robustness of the hardware itself (temps swing from the occasional -20 to +110 deg f throughout the year).
  5. tlj

    tlj Network Guru Member


    The Linksys WRT54G(S) radios in the Rootenna 19 db antenna work great.

    One thing nice is you are not working with coax - just ethernet.

    Re temps, I am in North Idaho and have temps like yours - had no problems during my testing last year and winter.

    The only thing I have found is there is no need to push avove 125 milla watts on the client side (it could be because my base stations have very very good ears).
  6. xrattiracer

    xrattiracer Network Guru Member

    thats very interesting, the temps are similar because im very close to you :) I live in north idaho and work in ne washington.
    sounds like some very encouraging results out of a package that costs a fraction of a "traditional" setup like ours.
  7. tlj

    tlj Network Guru Member

    n idaho


    Hmmm - let's seee.... you live in cda area and work in spokane area

    Wonder if I know you....

    Tom Jones
    Currently - Broadband Operations Manager for CDA Tribe
    Past - engineer at dmi.net in cda (first ISP in n idaho)
  8. t4thfavor

    t4thfavor Network Guru Member

    theese routers work great over long distances because there is an ack tweak built in to dd-wrt.

    what i mean is the router can listen longer for a packet before retrying because it takes longer for the packet to go 10 miles. the alchemy firmware besides being "sucky", does not have this.

    if you want to do this implementation you better get buying. the wrt54g(S) are all going to be gone soon. and you will have to use v5 which wont work.

    if you are concerned about heat build in a fan. I did and so have many others. there are also hacks that allow thermal control of fans and remote on/off switching. It just depends how ambitious you are.
  9. xrattiracer

    xrattiracer Network Guru Member

    Tom, i doubt that you know me, i havent been in the industry long. I am just a systems tech at a spokane wireless isp (which considering the way management is around here and the fact that i am kinda looking for other means of employment, should remain anonymous).
    t4thfavor: fans arent a solution that would do any good here. the antennas are completely sealed enclosures that have no provision for airflow, nor should they since they are outdoor units completely exposed to the elements. nor do i think that the routers generate enough heat (even at high power levels) to require cooling. I am concerned with the potential effects of solar heating of the enclosure.
  10. ronin99

    ronin99 Network Guru Member

    Interesting...using WRT54g over long distances. Where would the best place to start reading up on how to do this?

    Questions I initially have are:
    Do you need a completely clear unobstructed view, direct line of sight between the units?
    What's the best antennas to do this?

    Any info would be appreciated.


  11. t4thfavor

    t4thfavor Network Guru Member

    measure the temperature of the box with the unit off then turn it on at high power. In a completely open area my wrt gets warm to the touch and hot if you touch the processor. there is enough going on to create a significant amount of heat.

    you should allow for ventilation even through a baffled system or some other controlled way. it will make your life easier.
  12. xrattiracer

    xrattiracer Network Guru Member

    hot being... what temperature? most electronics can and will operate just fine at a temperature that would give you a mild burn when you touch it, so dont think that just because it feels hot to the touch that it is in any way "overheating".
    ronin: yes, you need a clear line of sight, microwave radiations is absorbed by water (and trees contain alot of water). the best antennas depend on the type of link (point to point, point to many, etc) and distance of the link. places like www.pacwireless.com have a large selection of 2.4 ghz antennas that are designed for wifi links.
  13. t4thfavor

    t4thfavor Network Guru Member

    excess heat is never good for an electronic component.
    and yes they can survive this heat, but how long. search this forum for people who have burnt up there routers with excessive power output.(which causes heat)
  14. tlj

    tlj Network Guru Member

    wrt54g(S) are all going to be gone soon

    t4thfavor, (re your post: 2006-03-03, 07:15:35)
    "...wrt54g(S) are all going to be gone soon..."

    Yup, was a tad bit worried about client radios changing on me. So, I have 800 Linksys WRT54GS radios in my inventory right now.

    You get a pretty good price when you order 800 Linksys WRT54GS radios, 800 Rootennas, 800 power injectors and 800 masts in one order.

    Guess the cats our of the bag now that I am really serious about delivering wireless broadband in North Idaho.
  15. t4thfavor

    t4thfavor Network Guru Member

    Re: wrt54g(S) are all going to be gone soon

    thats funny.

    i am also wrong. i have heard that there is a wrt54gL with L denoting Linux version retailing for $70 and having the 4.0 hardware revision.
  16. Kulai

    Kulai Network Guru Member

    Hi tlj,

    What type of AP you are using at your mountain tower? What is the "official" range this AP supposed to be able to reach and what is the AP power? I am trying to have a point-to-point connection for a 1.5 mile distance. I have a 15dbi omni antenna at my AP and a 20dbi Yagi antenna at my client. I have a constraint on placing my device near the antenna because of lightning. My area is very lightning prompt. To have line-of-sight, my client antenna is more than 70 feets high and I am using LMR-600 cable. LMR-600 will have insertion loss of 3.5dB over 75 ft. My AP end also have about same length of LMR-600 cable. I think my high gain antennas is able to compensate some signal losses. If you can reach 10 miles away, do you think I should be able to reach just 1.5 mile even with this long antenna cable?
  17. tlj

    tlj Network Guru Member


    The AP I am using is a Vivato VP2210. It is a great AP but the company just closed.

    Re: What is the "official" range
    Answer - a hell of a long ways. I have many clients over 10 miles.

    Re: what is the AP power?
    41 dBm typical @ 802.11b rates, 21dBi antenna
    (12,589 Milli-Watts EIRP)

    37 dBm typical @ 802.11g rates, 21dBi antenna
    (5,011 Milli-Watts EIRP)

    Re: I have a constraint on placing my device near the antenna because of lightning.
    Answer - I don't use coax for anything except the 1/2 foot to reach a radio. I do use lightning protection on everything.

    Re: do you think I should be able to reach just 1.5 mile even with this long antenna cable?
    Answer: Yea, I think it should be able to connect just fine.
  18. Kulai

    Kulai Network Guru Member

    Thank you tlj for your respond.

    Seems like Zeus like to play around my area more often than other places. My home had direct hit by lightning before. No lightning surge protector can stop a direct lightning strike. With electrical energy flowing near the high antenna will attract lightning.

    Unlike the high power AP you have, I am only using the consumer based products. I have a pair of WAP54G with 1 as AP and 1 as Client. I didn't know about 3rd party firmware until about 10 days ago. Had I knew this earlier I would have bought a pair of WRT54G because there isn't much 3rd party firmware for WAP54G. I even have a pair of 500mW amplifier but they didn't help much.

    Will try with a pair of WRT54G this weekend with DD-WRT V23 and report back.
  19. cdaga

    cdaga Network Guru Member

    Hi tlj

    I am intrested in how you are setingup the links at distance of 10 miles plus, I may be required to setup a 23 mile link, clear line of sight,

    do you only use ddwrt ?
    how do you set up client mode
    what is the thruput that you achieve?
    do you make changes to RTS and fragmentation ? if so what and how?

    I have often heard people talk about timing issues .. how do you get around them.

    btw .. I will be using WRT54GSv4 with 27dB antennas,


  20. tlj

    tlj Network Guru Member


    Are you in the North Idaho CDA area?

    Business wireless links . . .

    (note - I am pulling these numbers out from memory - it is up to you to verify my numbers)

    First rule for any business links (close and long distance). You need 20 db for overhead. If you can't get a connection with 20 db more signal strength than needed, then don't do it.

    Example, lets say brand X radio looses any connection at -86 db. I would install brand X radio at 66 db and better only.

    For any business, you need the extra 20 db signal strength to maintain 24x7 hours of operations under all conditions.

    So, for your question about a 23 mile link - - - (I assume business you want 24x7 connection)

    First things to calculate on this kind of a distance (802.11b/g)
    - You are going to loose 132 dB in your wireless links
    - You need an ACK timing of support of about 80,000 (round trip and overhead)
    - Using a 27 dB antenna and accounting for connector/cable loss - I guess you can legally use a radio with a power transmit setting at 50 mw.

    I estimate that 50 mw into a 27 dB antenna will get you to 23 miles with a -88 signal strength. You might connect and you might not. Even if it connects, you have no overhead for bad weather conditions. (If you are not worried about FCC rules, you might try using a xmit power of 1/2 watt up to 1 watt using amps).

    So, If you are going to try a 23 mile link, you have some base information.

    If it were my link, I would not build it using Linksys stock hardware at both ends of the link... I also would consider trying to locate a 6 foot dish (very high db gain)

    Now reguarding your question about my links, I use base station radios that can receive at almost -100 db signal strength.
  21. tlj

    tlj Network Guru Member

    Almost forgot...

    Things can go wrong at anytime. To avoid having to roll out at 2:30 AM to fix a down wireless network . . . consider installing two parallel wireless links to any location which must be connected 24x7. I use dual connection links and Cisco spanning-tree on my dual links. If I loose a radio link, the fall-back link kicks in.
  22. cdaga

    cdaga Network Guru Member

    Thanks for the reply

    Nope not in Idaho in fact not in the same country :)

    Located half way across the world in India,

    132 db is what i had calculated , Have 2 nos of 31db antennas (they are huge), Have to put up a 20 foot tower at one end to make sure that i get a line of sight, also plan to use the antennas in horizontal polorization.

    and yes I am planning a redundant link if the first link works out.

    Have to look at getting better ap's now (maybe will try with the linksys to see if it is possible to do)


  23. cdaga

    cdaga Network Guru Member

    btw .. how do you calculate the ack timing ?

    i have a clue on how to calculate the rts.


  24. tlj

    tlj Network Guru Member

    calculating the ACK value

    Try adding this for a starting ACK setting:
    1) Round trip distance in meters (plus 10%)
    2) Add additional 1000

    This should get you close for starters. My findings are it is better to be a little higher than to use a ACK value which is to low and gets you into problems.

    After the link is up and running, place the link under a heavy load and then start playing around with the (AP and client) ACK settings to fine tune what works best. The AP and client should both have the same ACK settings for this point-to-point network.
  25. cdaga

    cdaga Network Guru Member

    i got a test link running using 2 wrt54gl's , 31dBi dish antennas, now waiting for the client to ok purchase of better equipment
  26. foq99

    foq99 Network Guru Member

    Damn, this almost makes me want to vacation in NoID to check out these setups. Just wanted to quickly say something about the temperature issues. If you get a Peltier unit or something inside the sealed boxes, it might help to cool and heat the electronics. I don't really know how those things work, but I know that a simple power flow reversal would flip it from cooling to heating. I also know that those things run cool enough to frost up pretty quickly. The only issue would be making sure that your heatsink was big enough to handle the heat these things put out. But if you hook one side to the external (metal?) housing, that shouldn't be a problem.

    I'd guess you're running on solar power out there, so the hotter it gets, the better you can cool down the box. Just hook up a thermal regulator so you can tell it when to turn on and when to flip from heating to cooling. I'm not sure if you'd need a peltier or anything this extreme, but it'd be a cool project :)
  27. vincentfox

    vincentfox Network Guru Member

    A simple passive neatsink is about all you need, elaborate fans and peltier rigs are not needed for devices in the 3-8 Watts range and in fact would be adding another point of failure.
  28. tlj

    tlj Network Guru Member

    solar power

    solar power ?

    Solar Power is for the way out back country.

    Here, It only cost me about $130,000.00 to get electricity to the tower. (The one shown in the picture)

    Re- vacation in north idaho. It is a vacation every time I have to go work. Have to watch out for the deer, elk and turkeys. They can jump out at you when you are driving.

    While driving my argo 8x8 to the towers, I have encountered hundreds of deer, moose, elk and run into a few bears.


    My argo is like the one in the URL. It is the only way to get to the towers in the winter.
  29. cdaga

    cdaga Network Guru Member

    been some time since i posted in the forums but just wanted you to know
    i setup the link and has been running with out problems since april this year.

    did use wrt54gl's and tested the link.
    currenly have two links in place for redundancy using the wrt54gl's

    thruput achived 2.5 Mbps -

    will have some snaps up at my blog soon and will post link to them here


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