Questions tagged [path-loss]
15 questions
27
votes
4 answers
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
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8
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2 answers
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 azimuth.
Given the two angles I can derive 2…
gabriel-shatana
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6
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4 answers
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 1.5dB. At 8W, the power from the radio is 9.03dB.…
KM4NTK
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6
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1 answer
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 it is the equation it is.
Phil Frost - W8II
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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 hit it from there, but I can hear it, which for…
CJ KE4EDD
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3
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4 answers
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 with the airborne receiving height of the…
user5349
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3
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1 answer
2 meter and 70cm OSCAR expected signal attenuation by topocentric elevation angle, chart?
On average, is there a chart, or formula, which shows an expected signal attenuation due to the elevation angle to the satellite's position? I understand that range (distance) is also going to affect the signal path, so in order to simplify the…
always_learning
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3
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1 answer
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 at the 2 meter band, and there are houses and…
Skyler 440
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3
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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 0.6 dB, very few listings actually specified its…
natevw - AF7TB
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2
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3 answers
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 identical and have the same Tx power, shouldn't…
epv
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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 professor asked me to apply the log-distance path loss…
luw
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1
vote
1 answer
How to calculate passive repeater gain?
An active club in my area moved its repeater to a new location behind a big hill, and we can't join the regular social nets anymore. I'm not holding my breath that anyone in the gated HOA at the top of said hill would let me install any sort of…
natevw - AF7TB
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Building a ray tracing path-loss propagation model of LTE for small cells (pRRus)
Phones will receive signal from many pRRus. Should I average the antenna gain and all the path-loss (both line of sight and no-line of sight)? Or should I sum them all together?
Derrick
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1 answer
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.
Scenario 1
TX antenna sealed in a small bottle…
luw
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1
vote
2 answers
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 an antenna w.r.t. the frequency of…
eecs
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