Questions tagged [propagation]
Questions about RF propagation including measurements, beacons, modes (ionospheric, tropospheric, ground wave), etc.
135
questions
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Why am I receiving a local tv channel on a CMB frequency
I am using a simple Baofeng H6 dual band radio and I programmed weather channels.
Well, on frequency 161.77500 I am actually picking up WGN, a local tv network.
This frequency should be reserved to ...
0
votes
1answer
54 views
why does time of day affect propagation when talking to the other side of the earth?
i have been told time of day matters for hf propagation. for example, 80m works best at night. but if i qso with someone on the other side of the world, it's daytime. do they just need more power? can ...
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2answers
164 views
Sanity check: Should I be able to hear this 20m beacon?
I’m in Sacramento and have an EFHW antenna about 30’ up. I expected to be able to hear the W6WX 14.100 beacon without issue but I cannot. The distance is about 140 miles and the beacon transmits its ...
1
vote
3answers
93 views
Radio Waves propagation (Intuitive Understanding of Wave propagation)
I have few similar questions regarding Radio waves communication particularly FM and AM type of Radio wave communication. Please bear with the naivety of the questions.
Questions:
Radio waves in FM ...
1
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1answer
96 views
How Does the Propagation of H-pol E-M Fields Compare to That of V-pol E-M Fields (other things equal)?
A rather popular belief on this topic is that h-pol is superior to v-pol. Probably that is traceable to published "far-field" patterns over a lossy ground plane generated by Method of ...
0
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2answers
181 views
Why does the HamQSL website say the 40m band is fair and the 20m band is poor during the day?
http://www.hamqsl.com/solar.html
Why is 40m shown as "fair" while 20m is "poor" during the day. Shouldn't 7 MHz be getting absorbed by the D-layer more than 14 MHz?
10
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5answers
2k views
Non-traceable radio emitters
There are various techniques for locating a radio emitter. But what are some methods to make this really difficult? There is usually a patch to every vulnerability, at least from the world where I ...
-1
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1answer
175 views
Transmit data over HF signal 10,000km away [closed]
I would like to transmit trinary data (-1,0,+1) on 20-30m wave to be received 10,000km away. From Europe to US.
My first thought was this: https://www.researchgate.net/figure/Burst-modulation-mode-f-...
1
vote
3answers
231 views
Long range HF polarization
Is it possible to polarize HF signal (20-30m) at long range (thousands of km)?
It was commented in my over questions that polarization is not feasible at long range. However in this article is ...
1
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2answers
89 views
Hexbeam receiving in other directions
Have a K4KIO Hexbeam up at around 20-feet on the corner of a flat metal roof pointing at 290-degrees bearing (Europe, from Sydney Australia). Currently the Hexbeam is fixed to that direction as i don'...
0
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4answers
211 views
Send on-off radio signal 5,000km
I remember long range radio stations which still worked 30yrs ago. I could listen to the whole Europe. I also think I saw movies where radio enthusiasts could talk all over the world..
I never looked ...
4
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3answers
75 views
What kind of antenna for an automatic high bands monitoring station?
I would like to monitor NCDXF beacons, and WSPR. What kind of antenna would be good for reception in the bands of 6, 10, 12, 15, 17 and 20M?
Some antennas I considered:
A trapped dipole, with traps ...
1
vote
2answers
182 views
What is the best time of day to contact Japan from the east coast?
What are the best times in early April to contact Japan on 40M and 20M from Pennsylvania?
0
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2answers
227 views
Loop on ground for transmit?
If a large horizontal loop antenna, insulated but laying at ground level, works as an MF and low HF receive antenna, why (even though it has very high ground losses) can't it be used for transmit (to ...
3
votes
2answers
403 views
What is the radiation pattern of an ~60 foot end fed wire antenna used for 40 meters?
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 ...
5
votes
1answer
153 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 ...
3
votes
2answers
783 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 ...
5
votes
2answers
157 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+...
1
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0answers
75 views
HF propagation prediction using machine learning
Anyone out there know of or developed s/w to predict HF conditions using ML?
5
votes
1answer
147 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 ...
0
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1answer
95 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 ...
4
votes
2answers
308 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 ...
3
votes
2answers
89 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 ...
10
votes
6answers
250 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 ...
0
votes
1answer
138 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 ...
2
votes
1answer
76 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 ...
2
votes
2answers
1k 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?
6
votes
2answers
83 views
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 ...
2
votes
2answers
154 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?
5
votes
5answers
1k 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 ...
3
votes
3answers
139 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 ...
3
votes
3answers
723 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 ...
3
votes
2answers
165 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 ...
4
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3answers
2k 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 ...
4
votes
1answer
96 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 ...
3
votes
1answer
2k 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 ...
8
votes
4answers
577 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 ...
5
votes
4answers
4k 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 ...
5
votes
1answer
717 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
80 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
votes
1answer
683 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 ...
1
vote
1answer
172 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)...
3
votes
2answers
419 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 ...
1
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1answer
119 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
174 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
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0answers
32 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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3answers
204 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?
4
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1answer
200 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 ...
0
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1answer
99 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
51 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 ...
