Will a typical motherboard onboard WiFi circuit supply adequate power for a
directional WiFi antenna (13 dB or whatever)?

Is there some limit users should be concerned about?

https://www.amazon.com/gp/product/B015QF7EMK

"Max Input Power: 100W" ???

Thanks.

In article <s96trk$tdb$1@dont-email.me>,
John Doe <always.look@message.header> wrote:
>Will a typical motherboard onboard WiFi circuit supply adequate power for a
>directional WiFi antenna (13 dB or whatever)?

The motherboard (or USB, or PCI) transmitter circuit provides whatever
amount of power it provides.

It will provide the same amount of power into a 13 dBi directional
antenna, as it will into an ordinary "no gain" omnidirectional
antenna, or into an on-the-PC-board antenna (assuming that all of
these antennas have the correct design impedance of 50 ohms).

The directional antenna simply directs the available transmitter power
in a single direction. It'll beam about 20 times as much power in
that direction as an omni would (at the expense of sending far less
power in other directions). You'll get 4-5x (rough guesstimate) the
range with an antenna like this than you would with an omni.

>Is there some limit users should be concerned about?

The FCC places transmitter-power limits on Part 15 devices such as
WiFi transmitters. The limits vary by frequency and usage
mode... typically on the order of a watt to a few watts. If you buy an
illegal high-power WiFi amplifier, and exceed these limits, and somebody
complains about inteference, there's a theoretical possibility that you
might be cited by the FCC for illegal operation of an uncertified radio
transmitter.

The FCC used to require that transmitters (e.g. WiFi cards) and their
antennas must be certified as a single unit, and didn't allow swapping
of antennas. My impression is that this is a rule far more honored in
the breach than in the observance :-)

>https://www.amazon.com/gp/product/B015QF7EMK
>
>"Max Input Power: 100W" ???

That simply tells you that the antenna may be damaged if you try to
feed it more RF than the specified limit. All antennas have internal
losses (the RF turns to heat), and at high power levels the heat
buildup could damage the antenna, or arcing could occur,

Also, at that sort of high power level, you'd be exposing anyone or
anything standing near to the antenna (especially in front of it)
to possibly-dangerous levels of microwave radiation. The FCC has set
limits for acceptable RF exposure, in both controlled environments
("if you're there, you know what you're getting into") and uncontrolled
environments (i.e. if someone in the general public can wander into the
RF zone without knowing it).

You won't damage the antenna (or cause it to misbehave) by connecting
it to a typical less-than-a-watt WiFi card.

On 2021-06-02, John Doe <always.look@message.header> wrote:
> Will a typical motherboard onboard WiFi circuit supply adequate power for a
> directional WiFi antenna (13 dB or whatever)?
>
> Is there some limit users should be concerned about?

losses in the coaxial cable.

> https://www.amazon.com/gp/product/B015QF7EMK
>
> "Max Input Power: 100W" ???

71V into 50 ohms... I wonder if they actually tested that.

> Thanks.

--
Jasen.

dplatt@coop.radagast.org (Dave Platt) wrote:

> It will provide the same amount of power into a 13 dBi directional
> antenna, as it will into an ordinary "no gain" omnidirectional
> antenna, or into an on-the-PC-board antenna (assuming that all of
> these antennas have the correct design impedance of 50 ohms).
>
> The directional antenna simply directs the available transmitter power
> in a single direction. It'll beam about 20 times as much power in
> that direction as an omni would (at the expense of sending far less
> power in other directions). You'll get 4-5x (rough guesstimate) the
> range with an antenna like this than you would with an omni.

I get it. The output has no idea what (antenna) it's connected to.

--

> You won't damage the antenna (or cause it to misbehave) by connecting
> it to a typical less-than-a-watt WiFi card.
>
>

In article <s98vek$d0j$2@dont-email.me>, always.look@message.header
says...
>
> > It will provide the same amount of power into a 13 dBi directional
> > antenna, as it will into an ordinary "no gain" omnidirectional
> > antenna, or into an on-the-PC-board antenna (assuming that all of
> > these antennas have the correct design impedance of 50 ohms).
> >
> > The directional antenna simply directs the available transmitter power
> > in a single direction. It'll beam about 20 times as much power in
> > that direction as an omni would (at the expense of sending far less
> > power in other directions). You'll get 4-5x (rough guesstimate) the
> > range with an antenna like this than you would with an omni.
>
> I get it. The output has no idea what (antenna) it's connected to.
>
>
>
>

Correct.

The power rating of an antenna is the maximum recommended power the
transmitter should supply to it. Any ammount less is fine. So from just
a fraction of a watt to 100 watts is fine for the 100 watt antenna.

There are several reasons for the antenna power ratings. If too much
power is applied the power can cause arc overs or over heating of the
components of the antenna.

On Tuesday, June 1, 2021 at 11:27:55 PM UTC-4, John Doe wrote:
> Will a typical motherboard onboard WiFi circuit supply adequate power for a
> directional WiFi antenna (13 dB or whatever)?
>
> Is there some limit users should be concerned about?
>
> https://www.amazon.com/gp/product/B015QF7EMK
>
> "Max Input Power: 100W" ???

100W= 100.000 mW and 10Log(100,000)=50dbm(illiwatts)

PC WiFi typical outputs 20-30 dBm.

Typical PC WiFi input sensitivity -80 to -70 dBm.

So those are your starting and endpoints. It only gets more complicated from there, much more complicated.

See:
https://www.advantech.com/resources/white-papers/d3088606-77df-4460-878a-634dae19e8ec

You'll have to step through all the losses to answer your question about the power being "enough."

And if you're lucky, the answer will apply most of the time.

Cable losses, at both transmit and receive, can be horrendous at those frequencies, same for path loss. See chart:
https://www.amazon.com/Low-Loss-Coaxial-Extension-Connector-GEMEK/dp/B07TDP7W6C?ref_=ast_slp_dp&th=1&psc=1

>
> Thanks.