Questions tagged [propagation]

Questions about RF propagation including measurements, beacons, modes (ionospheric, tropospheric, ground wave), etc.

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3
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0answers
26 views

Looking for a model or description of an EME channel

I am looking for any technical/scientifical/specialized reference describing in some detail the moonbounce for VHF/low UHF frequencies. More precisely, I would be interested in a paper or publication ...
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0answers
56 views

Understanding low MUF in VOACAP

I've started playing with VOACAP to better plan and predict conditions on 27 MHz (CB). To my utter astonishment, VOACAP says that I won't be able to communicate on that frequency, regardless of ...
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2answers
74k views

Which HF bands are best during the day and which are better at night?

I am rather new to HF operation and have recently purchased my first HF rig. I have read about bands being "open" and "closed" based on various conditions including time of day. As I have been ...
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2answers
327 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?
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1answer
103 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 ...
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3answers
292 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 ...
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2answers
367 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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8answers
7k views

What is the best time of day/Band to make a contact with Hawaii from the East Coast?

I need to get Hawaii for Worked All States, and live on the East Coast (Virginia). Furthermore, I have a poor antenna, and thus only the prime times of the day seem to really be opened for me. What ...
5
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2answers
229 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+...
3
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2answers
123 views

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 ...
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1answer
59 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
346 views

What is “Meter” referencing in “60-Meter Band”?

I know that there are various bands referenced in meters (or cm). My question refers to what exactly the word "meter" is referring to when identifying the 5MHz band? I know that the 60-meter band is ...
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2answers
229 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 ...
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3answers
298 views

How far the near-field reactive region extends from the transmitting antenna?

I am doing research on near-field harvesting. In my situation the transmitting antenna is a dipole antenna operating at 2.45 GHz and its length is 14 cm long. I am trying to find how far near-field ...
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3answers
104 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 ...
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3answers
3k 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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2answers
206 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?
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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 ...
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2answers
248 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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1answer
208 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-...
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2answers
111 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'...
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4answers
218 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 ...
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3answers
78 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 ...
3
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2answers
483 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 ...
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2answers
323 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 ...
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2answers
696 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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1answer
156 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
993 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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6answers
259 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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5answers
1k views

How does one know when band conditions are optimal and what factors to consider?

On many of the DX sites, one will find many variables for solar weather to include flux, A, K, sunspots, etc… I’d like to know how to read those and know what to look for. As I understand it, the sun’...
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0answers
76 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
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 ...
5
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1answer
149 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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6answers
3k views

Does iron ore in the ground affect my signal?

Mineral content in the ground varies from one place to another. I've visited places where the ground & waters were an orange-red shade from the high iron content; not good for trees either. This ...
2
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2answers
1k 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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1answer
97 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
6k views

Is free space path loss dependent on frequency?

Free space path loss is calculated as: $$ \left( 4 \pi df \over c \right)^2 $$ The presence of $f$ in this equation means that losses increase with increasing frequency, so there's an inherent ...
2
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1answer
264 views

How do I simulate a receiving antenna in EZNEC simulation tool?

I have a situation where I need to find receiving antenna impedance when it’s $\lambda/2$ distance from the transmitting antenna. Both are dipole antennas. Is it possible with EZNEC?
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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 ...
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2answers
92 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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1answer
98 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
139 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
88 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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2answers
373 views

What would propagation look like on Mars?

If we could get a few HF stations on Mars, what would the propagation look like? Thought shamelessly copied from this blog.
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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?
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2answers
102 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 ...
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2answers
435 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 ...
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7answers
12k 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 ...
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2answers
156 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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4answers
12k 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.