RT3070 wireless adapter adjust tx power??

1. You are probably right about this. Even some channels are blocked, depending upon the country settings.

2. There do exist high power devices. I have an alpha wifi stick that claims to be high power.

It will drain more than the allowed 500mA from your usb port.

Most pc's only care about the total current used on all usb ports, so on a pc this can work.

Wifi communication is bidirectional. It's useless to have a high power stick if the access point is unable to transmit in high power as well.

For some cheap adapters without external antenne, sending more power could extend the usable range a little. High power devices usually will have a good antenna as you don't want the RF radiation to interfer with the surrounding chips.

This topic has sort of gone dead but...

I have found a way that you can stop the Linux OS (using BT5 in a Virtual machine for a start) from limiting tx power...

What I want to know though is:

1.  Is it telling me the truth that you can put 1.1A@ 5 volts into a Kinamax TS-9900 without blowing it up?

     NOTES:

     -  It 'claims' to have a txpower of 5800mW with a 58dBi Antenna.

     Transmission Power: 5800mW @ 38dBm ± 1dBm - http://forum.lowyat.net/topic/2414082/all

2.  What are the signs that it is not copeing with the 1.1A of power?  Fire?  Smoke?  Burning Electronics Smell?  Heat?

These are very ambitious figures.

I doubt its posible to get 58dBi out of that antenna design.

I have a 32km wireless link, that has a 24dBi grid pack antenna on the roof, and the TX power is 29dBm, and we are limited to 2MBps, although it probably will do more.

With 2.4GHz, interference and close objects can cause the biggest loss of performance, despite the power settings.

Mark

Mark,

I have done tests in windows 7:

It can see a network about 2.5 km away in a dense populated area with 20 story buildings

I don't know if that can help work out the max tx power?

(only used one USB port .: 500 mA draw)

I'm pretty sure (from the numbers mentioned) the card has 20dBm power output, and the antenna is 17dBi. This would be how they derived their so-called "equivalent" of 5800mW (which is not true). It means if your antenna radiated outward equally, then yes you'd need 5800mW for the same range, but actually on a lower transmit power the antenna is directional and has a 17dBi gain for the same range but no longer in all directions.

I'm not familiar with many antenna topologies, but from a google search it does look like there is a topology that offers 17dBi.

Then why advertise it has 5800mW 58dBi ???

Why I first looked at the numbers, they don't add up.

Here's another catch though...

It claims range upto 5km.

http://www.moxa.com/newsletter/connection/2008/03/Figure_out_transmission_distance_from_wireless_device_specs.htm

Link above explains range of Wireless.

EDIT: Removed wrong answers.

I built a python script to do all the hard-work

from math import *
while True:
    txpower = input('Enter TX Power in dBm value: ')
    txgain = input('Enter TX Antenna gain in dBi vaule: ')
    rxgain = input('Enter RX Antenna gain in dBi value: ')
    rxsensitivity = 81

    if txpower >= 50:
        txpower_dBm = 10*log(txpower/1, 10)
        txpower_mW = 10**(txpower_dBm/10)
       
    elif txpower <= 50:
        txpower_mW = 10**(txpower/10)
        txpower_dBm = 10*log(txpower_mW/1, 10)

    base = 41.88*2442
    power = (txpower_dBm+txgain+rxgain+rxsensitivity)/20

    top = pow(10, power)

    answer = top/base

    print " Your Range is about: ", answer, " km!"
    print " "

Just put in anything you want to test and it will work it out.  It even converts the txpower to dBm when you put in mW

Here is a summary of new results using script above:

ANSWERs:

1. 100mW / 58dBi = 1097.10366882  km!

2. 500mW / 58dBi = 2453.19838186  km!

3. 5800mW / 58dBi = 8355.29261538  km!

4. 100mW / 17dBi = 9.7779467407  km!

5. 500mW / 17dBi = 21.8641535926  km!

100mW / 11dBi ( This is a different adapter I have) = 4.90058207752  km!

They are assuming that:

  i.  RX antenna has gain of 2dBm

  ii. RX antenna has constant -81 sesitivity

The next set of results are using some facts:

  i.  Most networks I can pickup have a rx sensitity between -53 to -79 dBm.  So lets pick a number in between: -71

  ii.  RX antenna - most corperate networks do not have 2dBm antenna gain  So I will say about 0.5 dBm for internal gain and such.

1. 100mW / 58dBi = 291.909122484  km!

2. 500mW / 58dBi = 652.728641126  km!

3. 5800mW / 58dBi = 2223.11364437  km!

4. 100mW / 17dBi = 2.60164279264  km!

5. 500mW / 17dBi = 5.8174501375  km!

100mW / 11dBi ( This is a different adapter I have) = 1.30391015413  km!

WOW!  Don't those numbers say something  

I can not pick up signals in Cairns, so that rules out the advertised 5800mW 58dBm

I can't see the 'Federal Parliment Free WiFi', so I guess that rules out 500mW 58dBm

I can't see any of the networks from  Wollongong

BUT I can see networks with-in a 2 - 4km radius from my house (which is in an undisclosed location).  So I guess that the accual tx power of this device is exactly what you said: 500mW 17dBi .

I guess one way to test what tx power is going into it will be to cut a USB cable and add a multimeter into the circuit.  I can get around to that later in the week I suppose. 

Thanks for any advice you gave along the way.  I will let you know how my testing goes in due-course.

If it is USB powered, then we know it is extremely unlikely that it really has 5800mW power output.

Given that, if you work backward, there is a 'possibility' that they are implying 'range equivalent to 5800mW but just in one direction'.

With that possibility, this means a 20dBm power output followed by a 17dBi antenna. 17dBi antennas do exist (not that I'm any expert in

antenna technology) for WiFi from a google search, so this seemed to add slightly more weight to the possibility. I seem to remember

while back you already confirmed that the device was set to 20dBm in software.

I could be (very likely) totally wrong, but I imagine you'd need to contact the manufacturer to be really sure.

The fact that they state the digits '58' in both 5800mW and 58dBi sounds like a typo - maybe they meant 38dBi (which is still not the

right way to state things but maybe they were implying a 18dBi antenna which is possibly a rounding up of 17dBi. I'm just playing

with their numbers, which is all anyone can do without further knowledge. It's all speculation, so really you'd need to check with

the manufacturer. Any of their figures could be a typo, leading any conclusion anyone makes to be wrong.

Regarding distance, anything could throw off the real world distances (antenna construction, loss in coax and connector, reflections.

I know that playing with the digits seems like one possiblity of error.  But when I looked at about 10 or so sites, it seemed all of them have it listed as '5800mW 58dBm', which in itself is a contradiction.

I don't know how to contact the manufacturer as they seem to be a ghost company.  Kinamax does not seem to exist unless you want to buy their product from ebay or other store.

The Box I have Specifically states:

5800mW Power and 58dBi antenna

I just looked at the box:  there is a link to a manufacture:  www.antmax.tw

I will look into this site.

I'd take these specs with more than a pinch of salt! First of all they are somewhat optimistic in terms of range, you can get a decent link over about 5km "line of sight", that is with no obstructions across clear space. Start to add buildings or any objects in the path and you won't get that. That's on a good day, if it rains, forget it! Possibly in space maybe.

There is of course the matter of licencing of course, these devices are meant to be licence exempt, but there are limits to both output power and ERP.

Thought we have had our hands on some high powered kit, that is 1W output into a 16dB gain antenna it's been covered by the organisation who's been wanting the link, though here in the UK we've added this to our group licence NoV for this.

5800mW output power is unresonable, there's not a way you'd get that sort of power out of anything off the shelf. As for receiver sensitivity it's not down to background noise levels really, -70dBm would be more realistic. However, there is the point that some access points are set up to ignore weak signals anyway, so your efforts at DX may be in vane.

http://www.element14.com/community/groups/amateur-radio-group/blog/2010/04/25/extreme-wifi

Cian

I think you should be able to work out that the manufacturer is not using english as a first language.

The descriptions are gramatically incorrect for a start.

Your calculations are based on solid reasoning , but the fact still remains that it has to be two way, so even if you were pumping 10kw out, the link wouldn't work.

just a minor note though ..

The next set of results are using some facts:

  i.  Most networks I can pickup have a rx sensitity between -53 to -79 dBm.  So lets pick a number in between: -71

  ii.  RX antenna - most corperate networks do not have 2dBm antenna gain  So I will say about 0.5 dBm for internal gain and such.

i      this is the Received signal strength at YOUR end.

II      See below. 3dBi gain isn't unreasonable. You are mixing terms. (dBm which is a measure of power, and gain which is in dB.)

The NZ Radio Spectrum Services has some info about maximum radiated (that includes antenna gain) at

http://www.rsm.govt.nz/cms/licensees/types-of-licence/general-user-licences/short-range-devices

I'm picking that the Australian equivalent is similar.

If you are interested in getting signal from a site, then you should be able to use a suitable device and directional antenna (Antenna gain is compared to a dipole radiating 360deg, and while you can get some gain from the design, its generally because its directional).

My setup uses a 800mW Ubquiti Bullet

http://www.gowifi.co.nz/wisp-client-radios/ubiquiti-bullet2hp-802.11b/g-800mw-outdoor-ap/bridge.html

24dBi Grid pack antenna

http://www.gowifi.co.nz/antennas/2.4-ghz/directional/2.4-ghz-24-dbi-die-cast-wireless-grid-antenna.html

The range to the site is 32km, and the Rx signal (at this end) is currently -64dBm (but drops to -74 if the hedge grows).

The site survey sees a few others, with a noise floor of -97dBm.

I think -81dBm Rx is a little low, and its quite feasible for the 'site' to use an antenna with 3dB gain. (3dBi)

Obviously with any frequency above about 50MHz its line of site, ie you need to see it.

2.4 GHz and lower will tend to bounce around off hard surfaces, but they don't really follow the earths curvature, so its approx 11mile (17km), unless you have some elevation.

Buildings and other materials will attenuate the signal, so careful placement is important.

regarding the USB.

5v at 500mA gives 2.5 watts.

I note a 500mW (27dBm) devices with 5dBi antenna is available as a USB device.

I think as Shabaz has indicated, that the 5800mW is the eirp (Effective Isotropic Radiated Power) ie the equivalent power required if you had a dipole...

I seem to recall some similar claims about audio power. The marketing department invented this peak power measurement, which of course is a mathmatically anomoly.

It made the speakers and amplifiers look great though.

Mark

So I guess that the end of the story is this:

DO NOT PUT 5800mW into the adapter!!!!  It Will Explode (or therabouts)!!!

Should I try it?  I know how to get rid of the software limits.

So I guess that the end of the story is this:

DO NOT PUT 5800mW into the adapter!!!!  It Will Explode (or therabouts)!!!

Should I try it?  I know how to get rid of the software limits.

Cain

Common myth.

Power is consumed or used, not put in.

Bit like a loaded trailer on a car, it requires x amount of power to move it.

if you stick a 1000Hp car on the front the trailer still requires the same power to move it.

However they derived the figures it doesn't really matter.

Is the device working for you.?

Mark

It works great!  I was just interested in the accual power usage.

Thanks for all help!