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11 votes
Accepted

Difference between antennas for Wi-Fi vs. ham repeaters

In order to use the same antenna design at different frequencies, "all you need to do" is scale all elements of the antenna proportionally to the difference in wavelength. For example, if you take a ...
Kevin Reid AG6YO's user avatar
  • 24.7k
6 votes
Accepted

Yagi vs Parabolic Dish for 2.4GHz Campus Wifi from 1,800ft away?

You can make a first order approximation by using typical WiFi ranges in combination with two free space path loss calculations. 802.11b/g has a typical indoor range of 150 feet. By calculating the ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes

Yagi vs Parabolic Dish for 2.4GHz Campus Wifi from 1,800ft away?

Depends on the particular Yagi or dish. Look for a published gain. Beware of low-quality manufacturers that publish erroneous data. Higher gain will correlate with higher probability of working. Point-...
Phil Frost - W8II's user avatar
6 votes

Where can I find a very long distance Wifi antenna with a range of 50-100 km? Or is it a DIY project?

As the comments on the question suggest, there are regulatory concerns that may be relevant. But those are dependent on jurisdiction, so let's not get into that. A separate question, tagged with your ...
Phil Frost - W8II's user avatar
5 votes

Beamwidth of omni-directional antenna with gain

According to Kraus$^1$, the directivity of an antenna with a given beamwidth can be approximated by: $$D\approx\frac{4\pi}{\theta_{HP} \phi_{HP}}$$ where $\theta_{HP}$ and $\phi_{HP}$ are the half-...
Brian K1LI's user avatar
  • 7,878
5 votes
Accepted

Is there a practical way for hams to participate in cellular-related technology advances?

Are there any cellular bands that are close enough to amateur allocation for off-the-shelf cellular modems/filters/antennas to work? Yep, thanks to the fact that what is a GSM band in Europe is the ...
Marcus Müller's user avatar
5 votes

Measuring energy density of 2.4 GHz and 5.0 GHz signals

I'm a math and computer science student, starting to mess around with using amplifiers and antennas to build long-range wifi hardware in my spare time. You're potentially breaking the law. In fact, I'...
Marcus Müller's user avatar
5 votes
Accepted

Transmission power of Apple Wi-Fi antennas (EMF and health)

Maximum permissible power output for Part 15 operation is 1W; Apple devices are known to use up to that limit. e.g. https://fccid.io/BCGA2589/Test-Report/WLAN-OFDMA-Test-Report-1-5691887.pdf The above ...
nhw76's user avatar
  • 166
5 votes

How does tuning in 2.4 GHz Wifi radios work?

Nobody can tell you how your specific 2.4 GHz Wifi chip works, as we don't know it, let alone its internals. However, reasonable assumptions can be made: WLAN of the IEEE802.11a variant has been ...
Marcus Müller's user avatar
4 votes

How does Wi-Fi antenna work?

The antenna in photo below is the 1st antenna of the question. It is supposed to be 1/2λ long (radiator+sleeve). However its length is 2x25 mm instead of 2x30 mm. The antenna will still work even if ...
abcd567's user avatar
  • 389
4 votes

How does Wi-Fi antenna work?

This is the 2nd antenna of the question (screenshot from video linked in the question). Below are simulation results of an antenna similar to the one above. Although simulated antenna is not for ...
abcd567's user avatar
  • 389
4 votes

How does Wi-Fi antenna work?

Between lengths of infinitesimal and one wavelength, the lobes in the radiation pattern become narrower. Here's a picture from antenna-theory.com: Notice how for the 1-wavelength antenna, the lobes ...
Phil Frost - W8II's user avatar
4 votes

What is the optimal antenna for a high altitude weather balloon?

I've never launched a balloon, but I'd guess gravity would keep the antenna oriented vertically so circular polarization is unnecessary weight. If you did want circular polarization, put it on the ...
Phil Frost - W8II's user avatar
4 votes

What is the optimal antenna for a high altitude weather balloon?

2.4 GHz is most definitely not the way to go, unless you very much know what you're doing. The free-space path loss over a fixed distance increases with the square of your frequency. Whilst one ...
Marcus Müller's user avatar
4 votes

4G extension cable and antenna height?

If you elevate the antenna, you will absolutely increase your range, provided that the feedline loss is low enough. The coax should be mostly vertical, or the coax loss could offset the height gain. ...
Mike Waters's user avatar
  • 8,071
4 votes

Is there an 802.11 Wi-Fi module that allows direct access to the PHY layer

"Wi-Fi" is a trademark referring to the 802.11 family and has layer2 definitionally baked in. If you want to roll your own layer2, you specifically do NOT want WiFi or 802.11 family chips. ...
webmarc's user avatar
  • 4,241
4 votes

miniature parabolic antenna

From this equation, for a passive antenna of 15 x 20 cm, you would expect a gain of under 14 dBi. $$ A_e = 0.15 * 0.2 = {G\lambda^2\over{4\pi}}$$ I don't recommend trying to make a reflector antenna ...
tomnexus's user avatar
  • 11.4k
3 votes
Accepted

Amateur Radio Long Distance Data Communication

The most accessible way to get digital communication at that speed is WiFi. You could use unmodified consumer equipment, or getting a ham license would allow you to use frequencies not usually ...
Phil Frost - W8II's user avatar
3 votes

My radio in the garage is temporarily shutting down the wifi when I key up

Sounds like the router is getting front end overload. Either your OCF dipole is too close to the router, or you are getting common mode current on the coax and it is radiating along the coax. A balun ...
user10489's user avatar
  • 6,485
3 votes

Making WiFi access point range shorter on purpose

For a device to register with the access point, it must receive a transmit signal from the access point (AP). This largely consists of the AP transmitting its SSID so that it can be detected by the ...
Glenn W9IQ's user avatar
  • 18.6k
3 votes

Will very close proximity to electrical wires affect radio signals?

Will the electrical wires seriously affect wireless signal performance? Yes, electrical conductors within the near field of an antenna will actually become part of the antenna and change its ...
Marcus Müller's user avatar
3 votes

Wifi inside a rocket

The biggest issue between stages is that wifi doesn't penetrate metal well. Engine bells and plumbing are generally metal, even if tanks and exterior airframe skin aren't. Since cables are highly ...
Zeiss Ikon's user avatar
  • 4,107
3 votes

Is it possible to boost WIFI signal?

It Is quite possibly illegal. Actually amplifying your router or extender wireless signal to extend its reach runs the risk of being illegal in many countries. Any wireless device sold in a country ...
Gil's user avatar
  • 283
3 votes

Antenna reciprocity how does an antenna increase receiving range?

So to start off: I (an electrical engineer who had to take classes on that stuff) regularly get sad when I read the packaging of Wifi equipment, because the marketing speech on that is so wrong it ...
Marcus Müller's user avatar
3 votes
Accepted

SMA Connector Impedance

Lots of questions here, let me try to cover them point by point. A monopole is half of an antenna. A real antenna is a dipole. The monopole needs a "ground plane" to replace the missing ...
user10489's user avatar
  • 6,485
3 votes
Accepted

Long Distance antenna feedline for UHF/2.5GHz signal

If you can incorporate a strong, thin coax into the tow cable, you could use it to connect directly from radio to radio. Wifi radios expect up to 80 dB of path loss, even 100 dB at lower speeds (+20 ...
tomnexus's user avatar
  • 11.4k
2 votes

Can I build a mini passive repeater to improve my WIFI reception at home?

While passive repeaters do exist, I don't think building one for your apartment would be feasible or useful. As you can see in that article, they are usually quite large. Moreover, a signal of -65 ...
Phil Frost - W8II's user avatar
2 votes

2,4GHz Spectrum Analyzer with wireless card

Probably not. Most radio equipment of this sort only gives access to the demodulated-and-decoded signal. The requirements for being an (uncalibrated) spectrum analyzer of this sort are essentially ...
Kevin Reid AG6YO's user avatar
  • 24.7k
2 votes

Acquiring specs on anntenas so as to mathematically model level curves in their transmission feilds

Most antenna manufacturers will supply you with measurement data of how much power is radiated in which direction. That is a perfectly normal thing to do, and it's much more likely you'll get one of ...
Marcus Müller's user avatar
2 votes

My radio in the garage is temporarily shutting down the wifi when I key up

I agree with user10489's answer but would like to expand a bit on what to do about it. A signal of some sort appears to be interfering with something associated with the router and there does not seem ...
Chris K8NVH's user avatar
  • 1,042

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