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Questions tagged [path-loss]

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5
votes
1answer
61 views

Why does adding 50-ohm BNC Ethernet terminator(s) in parallel to my 4-element yagi improve my radio's reception? (70cm)

I have this radio, with a rubber duck antenna, and a repeater twenty miles away to my north-northwest. If I set my radio on the top of a cabinet in my bathroom, I receive the repeater fine. I can't ...
3
votes
1answer
62 views

Is there a technical reason to sell an LNA without advertising its gain?

I recently bought a couple SPF5189 low-noise amplifier boards via an online marketplace. One thing that struck me is that while nearly all the listings highlighted the LNA as having a noise figure of ...
1
vote
1answer
38 views

Measuring S21 against TX-RX distance (a.k.a path loss modelling) with a network analyzer didn't give expected results

Task: Path loss modelling Target frequency: 433 MHz; Laboratory environment: in a basement where there were other equipment and metal shelves. A few acoustic absorbers were placed around the setup. ...
7
votes
2answers
111 views

How to derive antenna gain from radiation pattern

I need to calculate the antenna gain in both dimensions: azimuth and elevation. The datasheet of the antennas I am using has two different radiation patterns, one for the elevation and one for the ...
1
vote
2answers
90 views

True near field distance for a short monopole antenna?

Antenna properties: Height x Diameter = 3.3 inches x 1.4 inches Test Frequency: 900 MHz (Wavelength = 33 cm or 13 inches) I see some conflicting formulas to calculate the near field distance for ...
1
vote
1answer
36 views

Is it correct to apply the log-distance path loss model for an in-body radio propagation?

The application is an implanted sensor and I am asked to characterize the transmission channel. I did measurements with bio-equivalent liquid and got a plot of the path loss over distance. The ...
2
votes
3answers
282 views

RSSI on both ends of UHF Point to Point network do not match

My understanding of an RSSI reading is that it should equal Tx power - Tx feed loss + Tx antenna gain - pathloss + Rx antenna gain - Rx feed loss. If this is the case, if the radios at either end are ...
5
votes
3answers
685 views

What is the minimum signal strength I need to receive?

Let's say a transmitting station is using a 8W radio with a J pole antenna. The cable connecting the radio to the antenna is RG-58A/U and is 25ft long. At 144.075MHz, the attenuation of the cable is ...
3
votes
4answers
636 views

Why link losses are more as the antenna height decreases in ground to air communication, in v/UHF bands?

Theoretically free space loss is independent of the height of the transmitting and receiving antenna. However when link loss is calculated in ground to air v/UHF communication, the link loss varies ...
3
votes
1answer
99 views

Estimate Path Loss

I am wanting to setup a simplex path that is 7KM from base to base in relatively flat ground. How can I estimate the path loss, and what do the numbers mean when I find them? I am wanting to do it ...
4
votes
1answer
2k views

What does the Friis transmission equation represent and how is it derived?

I've read that the Friis transmission equation can be applied to calculate path loss in ideal space. However, I'd like to better understand the factors that define it and what it represents, and why ...
22
votes
4answers
2k 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?