Linked Questions

1 vote
0 answers
62 views

Interpreting the Friis transmission equation [duplicate]

In the Friis transmission equation, can you please explain the significance of the factor $$\left(\frac{\lambda}{4\pi R}\right)$$ and what it helps us achieve? Specifically in terms of path loss.
Max's user avatar
  • 123
27 votes
4 answers
5k views

What is a link budget, and how do I make one?

Like the question title says, what is a radio link budget? For what is it useful, and how do I make one?
user's user avatar
  • 4,878
9 votes
6 answers
8k views

Why is antenna aperture a function of wavelength?

Wikipedia says: It can be shown that the aperture of a lossless isotropic antenna, which by definition has unity gain, is: $$ A_{\mathit{eff}} = \frac {\lambda^2}{4 \pi}$$ We also see this emerge as ...
Phil Frost - W8II's user avatar
8 votes
5 answers
13k views

Wifi passive repeater (antenna to antenna connection)

I have two buildings. Building A has wifi (2.4GHz) infrastructure, Building B doesn't. One side of building B can pick up the wifi signal from building A. I want to passively extend the signal through ...
askvictor's user avatar
  • 191
9 votes
2 answers
1k views

Moon->Earth 433MHz link achievable digital bandwidth

Let's assume we have the following situation: Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz. Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
BarsMonster - R2AYN's user avatar
1 vote
1 answer
2k views

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

I'd like to increase personal security by receiving Wifi connections 50-100 km away from physical device location, with high decibel to milliwatts (dbm) reading to overcome path attenuation by foliage ...
user avatar
2 votes
2 answers
3k views

Field Strength calculations with known antennas

I can receive a calibrated decibel milliwatt signal level from the output of any antenna at a given frequency. With a given antenna gain (dbi) in the direction I want to receive the signal (...
Skyler 440's user avatar
  • 7,590
1 vote
2 answers
463 views

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

I was thinking of creating a 2.4 GHz WiFi wireless link with a directional, circular polarized antenna but I am not sure if that would work for such a long distance. The antenna cant weigh more than 1 ...
user avatar
1 vote
5 answers
385 views

How to learn about the physics behind propagation?

What are good sources for information about the propagation of RF that details the equations behind the curtain? I've been able to find some simple stuff on wikipedia but nothing fancy that I'm sure ...
Joshua Katz's user avatar
4 votes
1 answer
446 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
user40713's user avatar
  • 225
1 vote
2 answers
360 views

How to plot transmitter coverage area?

As an Extra class licensee, I should probably know this... I am working on a web application for repeater owners. I would like to include an estimated coverage area, provided they have entered all of ...
Joshua's user avatar
  • 375
1 vote
1 answer
336 views

building a relay for 5.8Ghz?

I'm interested in building a relay for analog video sent from an R/C aircaft. The idea is to get around obstacles like hills and increase distance a bit. Rather than just applying more power, I ...
kbyrd's user avatar
  • 145
2 votes
3 answers
341 views

Is 2.4Ghz good for an UAV?

I'm designing a drone(UAV) as a hobbyist, and radio communications is not my strong point. I will be transmitting waypoints from a portable control station and receiving video(a low frame rate is ok). ...
Aaron's user avatar
  • 21
2 votes
3 answers
151 views

Wireless signal strength explanation needed

Could you kindly explain me or advise following please... I have a TP-link WiFi router. When I measure signal strength just in the vicinity of the router- literally I touch my smartphone (with WiFi ...
mariolucas's user avatar
3 votes
1 answer
256 views

How much RF power should I expect to receive from a satellite?

I am trying to receive beacon from the analog satellites and observe its power on signal analyzer.I am using a 15dB gain and LNA with a 40dB gain. I am trying satellites like Ho-68(-81.64 dB at 56 deg ...
Girish's user avatar
  • 31

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