1 vote
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.
• 123
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?
• 4,878
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 ...
• 51.7k
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 ...
• 191
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 ...
1 vote
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 ...
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 (...
• 7,590
1 vote
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 ...
1 vote
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 ...
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?
• 225
1 vote
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 ...
• 375
1 vote
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 ...
• 145
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). ...
• 21
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 ...