9

Satellite engineers tend to use circular polarization for two reasons: When a linearly polarized signal travels through the atmosphere there are anomalies, such as Faraday rotation, that alter the polarization of the EM wave. The geographic reference of the satellite polarization changes for a non-stationary satellite as it traverses its path above the ...


8

Summary If you can have only one antenna and can chose between a vertical HF antenna or a relatively high horizontal HF antenna, go for the horizontal antenna. Modelling results In January 2008, L. B. Cebik, W4RNL (SK) published what was going to be the last entry of his seminal 10-10 News series. It turned out to be an interesting gain comparison of single ...


7

It doesn't really matter. You're asking about a topic called polarization, which is really important in VHF and UHF. It's the reason why rotating your HT can improve or harm your reception, and it's also the reason why some 3D glasses and sunglasses work. But because of the way HF propagation works, it doesn't really matter. Any ionospheric propagation gets ...


7

I'm sorry if this answer doesn't answer your literal questions – it's just that these questions aren't strictly answerable. it is commonly known that electromagnetic radiation from an antenna is polarized; the electric field is parallel to the rod and the magnetic component is perpendicular to it. It is commonly known that antennas come in more shapes than ...


5

All radio signals are polarized. You can't not polarize an HF signal. The problem with HF is often we're considering skywave propagation, which involves reflections off the ionosphere and ground. Every reflection has the potential to alter the polarization. Furthermore, there are usually many possible paths from transmitter to receiver, involving reflections ...


5

It's a well-known fact among hams who use HF frequencies that horizontally-polarized RF waves reflect better off of ground than vertically-polarized waves. This explains why ground conductivity is so important to the performance of a vertical monopole antenna, and not as important for a horizontally-polarized antenna. I don't think this is true. Actually, ...


5

Why can I receive a vertically polarized signal on a horizontally polarized antenna on HF and vice versa? Who says you can? Cross-polarization is a common source of path loss even on HF. LZ1AQ has some experiments which show as much as a 25 dB difference between horizontal and vertical polarization. 25 dB is quite a lot, enough to make the difference ...


5

From your description: the vertical polarized antenna has no feed point. Since the antennas are orthogonal and on-axis there is almost no mutual effect, no coupling: the feed impedance of the horizontal antenna does not change. (2) No need for re-adjustment of the gamma match. (3) Not any effect from the vertical antenna parts. (4) No coupling, no power ...


4

For VHF, choice of polarization is not up to your desired radiation pattern, but who you want to be able to communicate with. In HF, the ionosphere causes random rotation of your signal's polarization, but in all line-of-sight communication, VHF or higher, there is no such rotation and a polarization mismatch can result in no signal at all. You should use ...


4

Reflections from the ionosphere are randomly distorted from the original polarization - but not circular. Polarization matters for ground waves but not for most sky waves.


4

RE: "I would also like to know why vertically-polarized waves propagate much better via ground-wave propagation than horizontally-polarized waves." This subject is treated in various textbooks relating to antennas and propagation. An example clip from one of them is shown below. The last sentence in the column on the far right-hand side of the clip is ...


4

From the Wikipedia article on HF: "Long-distance (skywave) receiving antennas can generally be oriented either vertically or horizontally since refraction through the ionosphere usually scrambles signal polarization, and signals are received directly from the sky to the antenna." Every RF signal radiated by an antenna is polarized. I believe you meant to ...


4

Welcome to HamSE, Gary, and thanks for an interesting question. We should be grateful to Russel Renaud, VA3RR, for posting his NEC2 simulation model of the DB2 antenna. Importing the model to the 4NEC2 simulator, we find that the antenna pattern is primarily horizontally polarized: Assuming the antenna is "in the clear" - that is, no other ...


4

It may help to be familiar with the concept of scattering parameters or S-parameters. The S-parameters are the elements of a matrix which tell you the amplitude and phase coming out of every port, for the signal going into any other port. It assumes all the ports are terminated in matched loads, and it's usually valid for only one frequency. For a 3-port ...


3

It is useful to use polarization of HF signals, but not for the same reasons you'd do that with a VHF signal, and the effects are radically different for groundwave vs. skywave propagation. Groundwave propagation is generally considered the same as line of sight, but this isn't strictly true, as line of sight is free space propagation, where groundwave ...


3

Yes, it is possible given two antennas at orthogonal angles to adjust the relative amplitude and phase between them and create vertical, horizontal, or anything between polarization. You can even create circular polarization of either chirality, or elliptical polarization. However, this does not solve the problem of the antenna interacting with the mast. ...


3

This question is on point. Let me make a quick excursion on how we physically model the rotating effect that the ionosphere has on linear polarizations. You have elegantly shown in a previous answer that you can decompose any linearly polarized wave into two orthogonal circularly polarized ones of equal magnitude. And that's exactly how we describe the ...


3

However, when they are pointed nearly straight up at a satellite that reference is effectively lost Satellite communications typically uses circular polarizations instead of linear (horizontal/vertical) for that exact reason; that's why when you open e.g. sat-TV feedhorns, you'll often find "snail"-shaped structures inside. With clockwise and ...


3

No. Reversing the conductors of the feed line produces a 180° phase shift (which is generally completely irrelevant) and has no effect on polarization. One way you could reverse the polarization without modifying the antenna would be to reflect the signal once.


3

What do you mean by reversing connection? If you just swap the ground and center wire of the feeding coaxial you create 180 phase shift, not change the polarization. The polarization of a helix antenna is determined by the rotation direction of the helix (right handed helix radiates right handed circular polarization). If you want to change the helix ...


3

reports it as "U: linear, V: linear" Satellites which transmit and receive at the same time frequently do one on VHF (2m) and the other on UHF (70cm), and they frequently have separate antennas for each (rather than a dual-band antenna). This notation is saying that the ISS's UHF and VHF antennas are both linearly polarized. What does this ...


3

From what you describe, it doesn't seem the vertical elements would be fed at all. Since they pass directly through the plane of symmetry of the horizontal elements they experience no electric field along the vertical axis, and so, aren't driven at all. It's as if they aren't there. Furthermore, there's a simpler way for the antenna to be "both ...


2

There are useful tidbits in all the answers so far. Here are a couple more. Not every ham has the good fortune to have conveniently spaced tall trees to hang horizontal antennas from. On 80 meters to function well, a dipole antenna would be about 130 feet long (a half wave). Distance above ground for optimal performance would be the same distance. ...


2

Yes, width and shape are relevant. It's mathematically simpler to assume that antennas are infinitesimally thin, however, and usually this is close enough to true that it makes a reasonable simplifying assumption. Antenna-theory.com has a good article on "thick" dipoles, summarized by this graph: Here, "A" is the thickness of the dipole, and the length of ...


2

I've always heard (but am unable offhand to quote authoritative research or provide an explanation of why this is so) that an advantage of horizontal for weak signal work is that a lot of man-made noise tends to be better received with vertical polarization than with horizontal. Thus, all else being equal, you will have better performance (i.e. a better SNR ...


2

A small horizontal loop will have two sharp nulls: one pointing straight up and one pointing straight down. That may: Help reduce losses in the soil directly beneath it Reduce the NVIS radiation directly overhead. On the lower bands, that could be a disadvantage if you want to work nearby stations, say, within a couple hundred miles. Lower the radiation ...


2

There is no issue with a horizontal small loop per se. In fact, if you want a horizontally polarized antenna with equal gain in the horizontal plane, a horizontal small loop is a great way to do it. A horizontally polarized dipole by comparison would have two nulls off the ends of the antenna. The nulls may or may not be useful for you. Nulls can be useful ...


2

I once wondered if a microwave oven magnetron might make a good transmitter, for CW for EME. I took a spectrum analyser and antenna to the kitchen and microwaved a glass of water, and I saw... The most awful collection of strong tones, covering a large part of 2.4 to 2.5 GHz, all of them shifting up and down in frequency, rising and falling, as the water ...


2

Paraphrasing the Wikipedia entry for the magnetron, we learn that, ... a stream of electrons passes by the openings to metal cavity resonators and causes microwaves to oscillate within, similar to the way a whistle produces a tone when excited by an air stream blown past its opening. The resonant frequency is determined by the cavities' physical dimensions. ...


2

The ionosphere conversion to circular is not particularly good - e.g. see cv.nrao.edu/~demerson/ionosphere/ionopol.html. This means that the circular polarization is very variable (ratio of major:minor axis signal strengths). Conversely the (linear) polarization alignment of most satellite signals is unpredictable from the receiver's point of view - maybe ...


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