Questions tagged [propagation]
Questions about RF propagation including measurements, beacons, modes (ionospheric, tropospheric, ground wave), etc.
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What is the radiation pattern of an ~60 foot end fed wire antenna?
I live in a retirement center. The rule here is “Never do anything anywhere at anytime.” That translates to “No Antennas” which I have been told means I can put out an antenna as long as it is ...
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1answer
114 views
Looking for a book that contained a circuit for receiving (literally) underground amateur radio transmissions
In this comment in Earth Science SE I've said:
This is a really cool question! I remember (a long time ago) reading about electromagnetic waves inside conductive soil that travelled near but below ...
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2answers
195 views
How to determine frequency and launch angle given a target skip distance?
I would like to communicate with someone 1000 miles (1600 km) away. I'm not sure how to target a specific distance.
(image source)
I assume it's an interrelation of the following factors:
Which ...
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1answer
75 views
What gain and power are required for successful DX contacts on 2m/70cm bands in CW?
I would like to practice in CW on 2m/70cm bands when and if there will be a tropospheric or sporadic-E propagation. However I don't have mush space for the antenna. There is a possibility to install 3+...
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54 views
HF propagation prediction using machine learning
Anyone out there know of or developed s/w to predict HF conditions using ML?
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1answer
110 views
Using shortwave communication, how difficult is it to transmit messages from the UK to the US?
Is it possible to transmit a short message across the Atlantic ocean from the UK to the US via shortwave? From what I understand, long-distance shortwave communication has lower bandwidth than other ...
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1answer
85 views
If i transmit on the same frequency using two separate transmitters joined together will they both add up in a reciever to produce a stronger signal? [duplicate]
If i were to use a passive transmit coupler to connect two transmitters of equal power output to the same antenna, and connect one microphone to both transmitters, and then transmit on both at the ...
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2answers
91 views
What causes the light and dark bands (of background noise) in an HF waterfall display?
While monitoring the 40-meter band (among others) throughout a typical day/night as propagation changes I have noticed there are often bands of very low noise (black area) and others with much higher ...
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2answers
83 views
What is really happening during RF ionospheric refraction?
We all know that the ionosphere — when charged — refracts RF energy, but why? In other words, what is actually occurring at a molecular level to cause radio waves to bend back to earth because of ...
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6answers
202 views
Practical limits to maintaining coherence in an HF channel
Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve.
It would be nice if one could simply take any existing modulation and slow it ...
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1answer
107 views
Vertical Antennas
I have just changed from a ground mounted Vertical antenna , to a MFJ-1796 Vertical antenna, due to not having big enough ground to bury as many verticals
as recommended. So far what I have found is ...
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1answer
44 views
Propagation Analysis with WSPR / RBN
I would like to analyze data from the Weak Signal Propagation Reporter (WSPR) and/or the Reverse Beacon Network to understand the propagation mode(s) of the recent welcome spate of CW and SSB contacts ...
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809 views
What is this burst transmission sequence across the entire band?
Fairly regularly on the 40m band I hear a quick blip of a tone, and when I look at the waterfall I see these brief transmissions all across the band that look like little dots. What is causing that?
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Propagation effects of noctilucent clouds
I know auroras are a propagation mode, but I was wondering with the recent outburst of noctilucent clouds (as reported on www.space.com) brings with it any interesting propagation modes, either on HF ...
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2answers
147 views
Restricted line-of-sight communication
Why do line of sight communication links have a restricted range for a given tower height? Is it only because of the Earth's Curvature?
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5answers
612 views
Loop antenna layout and radiation?
I've got, for the near term, limited resources to put up an HF antenna at my home. One of the options I can manage without excessive cost is a loop, which would enclose the house. I need to transmit ...
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3answers
137 views
Given the classical top down view, what does a bottom up view of RF waves look like?
Quote from Wikipedia, Photons: "Nevertheless, all semiclassical theories were refuted definitively in the 1970s and 1980s by photon-correlation experiments. Hence, Einstein's hypothesis that ...
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3answers
141 views
Line of sight from geographic/map data?
I have line of sight issues with repeaters I want/need to use (it's a repeater network my club uses). One of the options that might be available to me is to install a "passive repeater" in a location ...
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2answers
109 views
Is there a trick for reaching a repeater “through” terrain?
I live in a draw, well below local average ground level. There are two repeaters I want to be able to use (because they're in the network my club uses). One is in the 440 band, thirty miles away but ...
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1answer
571 views
How can I be sure I'm actually hitting the repeater?
I'm just starting to use 2m and 70cm bands, which normally use repeaters to extend range beyond a mile or two (limited mostly by line of sight, as I understand it).
When I'm at home, however, I'm not ...
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1answer
85 views
High-resolution GIS datasets of groundwave conductivity of the United States, besides the FCC?
The FCC publishes a map of estimated groundwave conductivity of the United States, but the resolution is quite low:
Are there any GIS datasets that include groundwave conductivity at a higher ...
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1answer
1k views
Where does the year 2019 fall in the sunspot cycle for HF propagation?
I am reposting this question about the year 2016 here. This is 2019.
Are we now at the good or bad portion of the 11 years cycle?
What effect are we seeing now?
How large (strong/deep) is the effect ...
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4answers
310 views
Better explanation for beyond-line-of-sight VHF signal reach than “lower curvature to radio waves”
I am currently studying for the Technician Exam and have come across an answer to a question I think is ridiculous. The question is:
Why do VHF/UHF signals usually travel somewhat farther than ...
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4answers
1k views
How far do radio waves travel?
I have read that radio waves just keep traveling but the signal gets weaker because of how the wave spreads. OK, I get this, but what confuses me is that satellites emit signals from space that our ...
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1answer
440 views
Why are the lower HF frequencies not working during winter day time?
Currently my location is Nepal. We use the ICOM f-7000 radios without the antenna tuner. We use the frequencies round about 5-9 MHz, for communication over distances between 150 and 400 km.
During ...
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1answer
76 views
Why does signal power drop every night?
I have been monitoring power of a P25 control channel (at about 850MHz). For awhile, 24 hours a day. I graphed the power over a couple of weeks and it is almost sinusoidal, decreasing significantly ...
5
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1answer
611 views
Do short waves pass through or reflect off concrete buildings?
I live in Moscow, Russia and use DIY indoor magnetic loop antennas to listen amateur radio. Recently I received quite strong signals from Italy (20m, IV3UTV) and Slovenia (40m, S51CK), both operators ...
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1answer
111 views
Is there any way in which elevation *does* affect medium frequency (AM radio) transmissions?
This is a followup to this question of mine. From reading the wiki article, I get that:
Radio waves at MF wavelengths propagate via ground waves and reflection from the ionosphere ( called skywaves)...
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2answers
335 views
Using approximate signal strength at a distance to estimate reception strength of a radio station
I have some historical data on radio stations, but unfortunately, the dataset only has these variables:
the power of the transmitter, in watts
the coordinates of the radio tower
Unfortunately, I don'...
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1answer
105 views
How is RF Power at Receive Antenna Output Terminals Calculated?
Is the Friis equation sufficient to make this calculation? Must other considerations also be evaluated?
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2answers
133 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 ...
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0answers
28 views
To decide coherent time and fade duration from measured received signal spectrum and relate them to channel modeling
This question was asked in Electrical Engineering 2 days ago but hasn't received very informative responses.
https://electronics.stackexchange.com/questions/387255/decide-coherent-time-and-fade-...
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200 views
Should Hams Using Skywaves Be Concerned About Their Groundwave Radiation?
Comments posted on various websites relating to amateur radio posit that the groundwave is unimportant for skywave paths. Is this concept correct?
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1answer
160 views
Two way ham radio to communicate between two stations
Apologies if this not the right place for this question.
I'm into electronics and now endeavouring into radios and communications.
Unfortunately I'm not sure what terms to use to find what I'm ...
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1answer
92 views
Does the E-field propagate faster that the H-field?
I need some proof that the electric (E-field) and the magnetic component (H-field) of a lightning stroke both propagate at the speed of light, and that there is not a significant delay between them.
...
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1answer
45 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 ...
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4answers
10k views
When will propagation on HF improve?
Will the propagation on the High Frequency bands come back up soon?? I am referring to the 3 to 30 MHz range.
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2answers
230 views
Communications : Ground wave propagation
I was studying ground wave propagation, my book writes the lines about it without explaining it. I really do not know any explanation for these queries coming in my mind. I've Googled it, and you will ...
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2answers
165 views
Can a Loop Antenna send and receive 10,000 miles away
Can we expect a Loop Antenna such as a Chameleon F-Loop Antenna transmit and receive from the USA's midwest to Australia on HF using an average 100 watt SSB transmitter and an average receiver?
If so,...
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2answers
224 views
How can Ground Penetrating Radar work?
I was reading about GPR devices recently.
Considering the operation frequency of these devices, how they can go that deep (up to 50 feet)? Normally you would only expect a Hz to KHz range signal to ...
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6answers
1k views
Can I talk 2 Meter VHF across the United States
Can I talk on 2 meters from the east coast to the west coast without using repeaters?
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2answers
292 views
How is it possible for an HF signal to go around the world when part of it must be in sunlight?
I believe most of us know about the ionosphere, and skywave propagation, but I'm kind of tripping up on the D-layer. If the ionospheric D-layer absorbs HF signals (40 meters, for example) during the ...
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2answers
143 views
Can you create a radio beam with a Faraday cage?
Imagine we have an isotropic antenna at the origin emitting a steady sine wave at frequency $f$. Encompassing the antenna is a sphere of radius $r$ made of a fine copper mesh (with holes $\ll\frac\...
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3answers
493 views
Why is VHF better than UHF in this situation?
One of the sample questions for the British foundation level test is:
An amateur has the choice of VHF or UHF for a particular contact of some 25km. Which statement below best describes his choice?
...
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673 views
Difference between Phase Velocity and Velocity of propagation in a transmission line
I'm confused by the difference between the phase velocity and transmission line propagation velocity.
From https://en.wikipedia.org/wiki/Speed_of_electricity, in a good conductor, phase velocity (...
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7answers
9k views
What is the cause of this unusually long period of terrible HF band conditions?
I've been a ham for over 40 years, but never has there been such a prolonged period of such poor propagation. This has been especially the case over the past six months or so, and they continue to ...
5
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1answer
441 views
Does geology affect radio signals?
following on from an earlier question about Iron Ore affecting radio waves... are there any other geological properties that can affect radio waves?
Are certain frequencies more susceptible to ...
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2answers
494 views
Troposcatter: really all that bad?
The previous question,
Packet Radio at 100 miles
and specifically, Phil's answer raised an interesting question:
In a 50–100 km distance situation where Line-Of-Sight beams aren't an option for ...
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5answers
295 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 ...
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4answers
783 views
How does VHF/UHF propagate beyond the expected (radio) horizon?
I am not asking about the fairly well-known effect of the earth "appearing less curved to radio waves" that are otherwise still essentially line-of-sight, but a deeper arcanum:
In the ARRL Antenna ...
