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Yash007
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Increase Output TX-power

Thu Feb 04, 2021 8:19 pm

Hello Guys,

I want to increase TX-power in my QRT radios to 27dbm than the default. So, what's the process and what mode do we have to use like all rates fixed or card rates ?

I tried card rates it is coming with the error that i can't modify it.
 
Cablenut9
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Re: Increase Output TX-power

Fri Feb 05, 2021 5:51 am

This is a little risky, but you can make the maximum power by doing this:
/interface wireless set antenna-gain=0
which fools the device into thinking it has a 0 dBi antenna which it doesn't. However, you might fry the radio by going that low.
 
mkx
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Re: Increase Output TX-power

Fri Feb 05, 2021 9:30 am

However, you might fry the radio by going that low.
Probably not. According to information from MT staffer, ROS picks lowest number of (card rates, country limit, manual Tx power setting) as Tx power at any rate used. So by setting antenna gain to 0 (and choosing country with most generous Tx power limitations) one effectively lifts the country limit ... the other two are still observed.
BR,
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bpwl
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Re: Increase Output TX-power

Fri Feb 05, 2021 11:39 am

Be careful !

QRT has antenna gain of 24 dBi , with TX power on 27 dBm you have a beam with energy density of 51 dBm , this is a beam with the power density like a 100 Watt omnidirectional transmitter (EIRP).
(Your microwave oven is 57 to 59 dBm omnidirectional inside).

Legal limits are usually around 30 dBm (1 Watt EIRP). ROS will not allow you to set a lower antenna gain parameter than the gain of the built in antenna. If you still can hack it to full radio power , you work illegal, and close to the unit you risk your eyes (Cataract). (It's like playing with a class 3 (or even class 4) 200 mWatt laser pen with invisible light)
 
Yash007
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Re: Increase Output TX-power

Fri Feb 05, 2021 5:38 pm

Be careful !

QRT has antenna gain of 24 dBi , with TX power on 27 dBm you have a beam with energy density of 51 dBm , this is a beam with the power density like a 100 Watt omnidirectional transmitter (EIRP).
(Your microwave oven is 57 to 59 dBm omnidirectional inside).

Legal limits are usually around 30 dBm (1 Watt EIRP). ROS will not allow you to set a lower antenna gain parameter than the gain of the built in antenna. If you still can hack it to full radio power , you work illegal, and close to the unit you risk your eyes (Cataract). (It's like playing with a class 3 (or even class 4) 200 mWatt laser pen with invisible light)
Are you saying it is not a good thing to set up that value ? The reason i am doing is i am using a omnitik 5ac antenna to reach 2 mile distance. Unless it is not at that power level it is not reaching the station radio.
 
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bpwl
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Re: Increase Output TX-power

Fri Feb 05, 2021 7:27 pm

Increasing the TX power so that "TX Power + antenna gain" is above the regulatory domain EIRP level is illegal, or is and should be made impossible.
Wifi communication is bi-directional. (Both directions need to be possible). So the TX power needs to be balanced on both sides.
Good news is that antenna gain is reciprocal. It works for transmission and also for reception.
Because regulatory EIRP limit reduces the TX power with the antenna gain, the emitted energy in a directional antenna in the focal direction is only as strong as an omnidirectional antenna.
The practical gain in a directional antenna comes from the "antenna gain" while receiving the signal.

The Omnitik 5 ac with its 7.5 dBi antenna will have difficulties capturing a far away signal. So boosting the QRT TX-power would improve that, but is illegal.
The QRT will have no problem receiving the Omnitik signal. (Actually the signal of the (legal level) Omnitik is as strong as that of a legal QRT in the focal direction)
The legal step is to replace the Omnitik, or add a directional device to capture the QRT signal. (https://mikrotik.com/products/ptp)
 
Cablenut9
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Re: Increase Output TX-power

Fri Feb 05, 2021 7:52 pm

Increasing the TX power so that "TX Power + antenna gain" is above the regulatory domain EIRP level is illegal
It depends on where you are. In the US with PtP links, the only restriction is that the output power can't be above 200W, which no Mikrotik device even gets close to.
 
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bpwl
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Re: Increase Output TX-power

Fri Feb 05, 2021 9:56 pm

FCC is indeed not my world. (Hard enough to learn and live with ETSI.) So maybe FCC users are free to use 53dBm , so go ahead.
No intention to study the FCC regulations, just reading some vulgarization , like https://www.air802.com/fcc-rules-and-regulations.html , what assigns high power to 2.4 GHz only.

And Omnitik 5 ac is 5 GHz only.
QRT (24dBi) at TX-power 29 dBm , has an EIRP of 53 dBm (200W)
 
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TomjNorthIdaho
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Re: Increase Output TX-power

Fri Feb 05, 2021 11:58 pm

You are almost always better off not changing the transmit output tx power.
Instead , get a better antenna.

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