Questions tagged [propagation]

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

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16
votes
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 ...
28
votes
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 ...
16
votes
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 ...
6
votes
1answer
607 views

Can tropospheric scatter effect be used by 802.11 links?

What are the lowest EIRP and antenna gain requirements that make possible use of troposcatter at the distances of 100 to 150 kilometers assuming conventional WiFi (6 Mbit/s data rate with OFDM/BPSK ...
15
votes
2answers
23k views

How do I make a RF propagation map for a repeater?

Let's say I have a repeater. Knowing all of the information about antenna height and gain in each direction, as well as power, how can I create a map similar to this map I saw of a repeater in ...
11
votes
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 ...
3
votes
2answers
424 views

How can I know over what distance or at what speed I can communicate? [closed]

Given some description of some parameters like: transmitter power frequency antenna location time of day how can I know over what distance communication is possible? Can I know the limits to these ...
16
votes
4answers
27k views

What bands and modes will give me voice at 3,000 miles?

I pursued Amateur Radio primarily for local emergency communications and as part of my electronics education. My only radio right now is an inexpensive 2m/70cm HT which is good for local weather ...
5
votes
2answers
7k views

Where year 2016 falls in the sun spot cycle for HF propagation?

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 during the peak and bottom of cycle? What will change in coming years?
3
votes
2answers
2k views

Longest achievable ground wave range on 40-meter bands [closed]

What is the longest possible range on the 40-meter band by ground wave? A reference said we can achieve 150 miles at 8 MHz with only a 100 watt transmitter. It also says on 160 meters, the ground ...
2
votes
2answers
1k views

High data rate on HF & MF bands

Is it possible to transfer data at a high rate, like 1-2 Mbps, on 0.5 - 30 MHz? From Shannon's Theorem, with a bandwidth of just 300 kHz it is possible to reach 1.5 Mbps. I want to use these bands ...
8
votes
5answers
18k views

How far can a 2.4 GHz, 1 watt signal go in a rural area?

What's the approximate range achievable by a 2.4 GHz signal of 1 watt in semi-urban areas? I can see 2 km from our rooftop. Will a 2.4 GHz signal go that far, i.e. if I send WiFi signals from our ...
3
votes
2answers
992 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 ...
10
votes
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 ...
9
votes
1answer
960 views

What are the general effects of a geomagnetic storm on propagation?

Per NOAA/NWS Space Weather Prediction Center, "SWPC Forecasters are anticipating G3 (Strong) Geomagnetic Storm conditions to occur January 9 and 10." What does that mean, very generally, for amateur ...
8
votes
3answers
1k views

What is the proper way to ground your station's antenna?

I don't understand how you would go about giving an RF ground to your antenna. Would it not become an additional radial and affect the signal? What is the proper way to ground your station's antenna?...
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 ...
5
votes
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 ...
4
votes
4answers
3k views

What does multi-path sound like on FM?

I know I have probably experienced multi-path propagation on FM modes when I was working a repeater in the grand canyon and in the mountains. How can I identify when I am getting multi-path, and what ...
3
votes
1answer
65 views

What are some reliable sources of propagation forecasts?

Where can I go to find propagation forecasts? How useful are propagation forecasts over time? For instance, I've been told by meteorologists that weather forecasts three days out generally ...
2
votes
3answers
560 views

Should I use ham or cb radio? [closed]

I've been scouring the internet for the answer and my question is never directly answered, usually there is a bunch of technical jargon. It is not that I am unwilling to learn, because I want to, but ...
11
votes
4answers
1k 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 ...
10
votes
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 ...
8
votes
3answers
7k views

Why is the electric field orthogonal to the magnetic field from an antenna?

I've read in several places that the electric field is 90 degrees orthogonal to the magnetic field, and both are orthogonal to the direction of the wave from a transmitting antenna. What causes this? ...
8
votes
2answers
261 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 ...
5
votes
2answers
2k views

Best QRP HF band for small antenna?

What HF bands, times of day and/or conditions might be best for attempting to make non-local contacts using QRP transmitter power (around 1 Watt) and a small indoor folded or loop antenna?
5
votes
1answer
543 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 ...
4
votes
3answers
8k views

How and why sunspots affect propagation in HF bands?

How and why do sunspots affect propagation in HF bands?
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 ...
3
votes
2answers
172 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 ...
3
votes
3answers
636 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? ...
3
votes
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 ...
1
vote
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 ...
0
votes
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,...