Talk:Shortwave radio

Note

This is a good summary on Shortwave and how it's used.

An annual conference dedicated to shortwave listening is the Winter SWL Fest, located outside of Philadelphia in the USA. Its URL is http://www.swlfest.com

Number of receivers

"The Asia-Pacific Telecommunity estimates that there are approximately 600,000,000 shortwave radio receivers in use in 2002."

I know there are a lot about but the figure seems extremely high, especially if we're talking about receivers actually in use as opposed to the total number ever produced or something. This works out at about one shortwave radio for every ten people in the world. Can anyone confirm it? — Trilobite (Talk) 04:24, 26 Nov 2004 (UTC)

• I can confirm that I personally own 11 shortwave radios.  :) bneely 19:27, 26 February 2006 (UTC)

Add Section on PC-Controlled Receivers and Software?

Suggestion: Anyone think it's a good idea to include a section on PC-controlled shortwave receivers (and software)? (I am not the prospective author, as no experience with this setup.) I didn't find any reference to it in Wikipedia.--Kibbitzer 07:11, 14 July 2005 (UTC)

• Only in conjunction with a general discussion of shortwave and amateur radio hardware, and a mention of Digital Radio Mondiale (which pretty much requires a computer anyway). Not a bad idea though, just needs a fair amount of background to go with it. Haikupoet 06:00, 15 July 2005 (UTC)

Yes. Perhaps zealot will contribute. Also, this is the first I heard of DRM. Perhaps the Wikipedia article on that could be appropriately linked? Again, I am not qualified to know where to work it into the existing shortwave article.--Kibbitzer 06:22, 15 July 2005 (UTC)

Better band descriptions?

This page needs better descriptions of the meter bands. For starters, I dispute the "not in the americas" label for the 41 meter band. I have other descriptions for these bands but I believe it is under copyright (from radio manuals). bneely 19:29, 26 February 2006 (UTC)

Ionosphere refraction?

I was reading the article and this part was unclear to me:

Shortwave frequencies are capable of reaching the other side of the planet because they can be refracted by the ionosphere. Are radio waves refracted (bent) or reflected? . User:Rjairam

They are actually refracted since the waves enter the ionosphere and their direction of propagation is gradually changed by interaction with the free electrons therein. However, for practical purposes, the interaction can be characterized as a reflection from a thin, conductive surface at a single virtual height above the earth. Jim, K7JEB 02:27, 13 April 2006 (UTC)

It is actually a dual process of refraction and reflection. As the ray enters the layer it bends - refraction and it eventually reaches a part of the ionosphere where the angle of incidence equals the angle of reflection and reflection back or out of the layer occurs and at his point refraction again follows until the ray exits the layer. If you were to plot the path of the ray through the layer it makes a curve. If pure refraction were to occur the actual location of reception is not at the predicted location but can be several hundreds of kilometres away. Proof that reflection plays an important role is that only then can the predicted zone of reception actually in over 90% of the time be reached. Other factors also play a major part but without reflection the ray would not be received where expected. I also happen to be a retired radio engineer responsible for long range (HF) communication and in the context that I refer to a "ray" it means radio wave.

Merger with High Frequency?

The shortwave and high frequency articles seem to be about the same subject:

• Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly in use at that time. An alternate name is HF, or high frequency.
• High frequency (HF) radio frequencies are between 3 and 30 MHz. This range is often called shortwave.

Shouldn't these be merged? If so, which title should be the "main" article title? — Johan the Ghost _seance 14:12, 23 April 2006 (UTC)

I'm making this a formal proposal. Please comment at Talk:high frequency. — Johan the Ghost _seance 10:35, 11 May 2006 (UTC)

Needs Improvement

This article fails. Lacks date when shortwave was invented and/or came into practical use. --68.190.117.179 00:15, 18 June 2006 (UTC)

• You're absolutely right; although there is an article called History of radio, and there is another called Shortwave listening, this would be a GOOD place to start a history of shortwave broadcasting ... although that's a very large subject in it's own right. Twang 02:18, 11 July 2006 (UTC)

Note on HF

The term "HF" is not misapplied; it's historical and has been in use for many, many decades -- particularly before VHF and UHF (which are no longer VERY or ULTRA) transmitting became commonplace. In fact the HF amateur radio bands were allocated to amateurs (like reservations were allocated to indians) precisely because it was once thought they would be of little use to broadcasting. Twang 02:03, 11 July 2006 (UTC)

Disambig

There needs to be a disambigulation page to differentiate between radio waves and other uses of "short wave" and "long wave" (such as those terms in Meteorology).

Globalize tag

I've added a globalize/USA tag to this article, since it is a particularly bad example of US-centric writing, especially in the first section. 86.31.35.135 (talk) 23:24, 11 January 2008 (UTC)

Can you support this with some basic elaboration? 71.228.184.188 (talk) —Preceding comment was added at 19:04, 4 February 2008 (UTC)

A good deal of the development of shortwave radio came from the United States first, especially in the 1920s. U.S. hams were the first to discover the ability of shortwave to reach long distances. GABaker (talk) 19:35, 4 February 2008 (UTC)GABaker 19:34 4 February 2008

File:Modern_Short_Wave_Radio.jpg may be deleted

I have tagged File:Modern_Short_Wave_Radio.jpg, which is in use in this article for deletion because it does not have a copyright tag. If a copyright tag is not added within seven days the image will be deleted. --Chris 10:23, 28 April 2009 (UTC)

Narrow-band FM

Because of the larger bandwidth required, NBFM is much more commonly used for VHF communication.

I thought that NBFM had the same bandwidth as AM. 72.75.98.88 (talk) 22:04, 4 June 2009 (UTC)

Power over Wireless

Some mention of this new technology would possibly fit here? 87.74.77.209 (talk) 21:14, 23 July 2009 (UTC)

Wavelength

Frustratingly, the first citation just doesn't support what is in the introductory paragraph of the article. What is the range of shortwave frequencies? Anyone know? —Preceding unsigned comment added by 173.2.230.224 (talk) 03:29, 1 July 2010 (UTC)

Reflection? Refraction? I'm confused

I'm driving along a highway. Ahead of me I see a car, and just below that in my visual field, there's a wavery sort of "reflection" of the car. I know that neither asphalt nor air has any reflective properties, but clearly this is "reflection by refraction" and analogous to the way shortwave radio gets bounced around the ionosphere. Is it really that clear-cut? --Wtshymanski (talk) 15:08, 2 September 2011 (UTC)

Yes. Light and shortwave are both electromagnetic radiation, and either can be reflected or refracted. My recollections at the atomic level are fuzzy, but at a gross level, they are very different phenomena, as different as a reflector telescope and a refractor telescope. One difference is that the angle through which a refractive media bends electromagnetic waves depends on frequency, while the angle of reflection for a mirror is independent of frequency. Jc3s5h (talk) 17:25, 2 September 2011 (UTC)

There's an awful lot of literature out there that has radio waves "bouncing" off the ionosphere like a puck off the boards. Are we really sure that using the esoteric, possibly correct form "refracting" is more accurate than the equally descriptive, familiar "reflecting" ? Surely the dependancy of refraction on frequency only holds true in a dispersive medium...(even if just about every thing *is* a dispersive medium). Why doesn't the car reflected in the pavement change color, then? Why does HCJB come in on the same frequency that they announce? Why does my face look funny in a red or green mirror? Maybe we should just say something like "the path of the waves is bending", which is clearly happening. --Wtshymanski (talk) 19:22, 2 September 2011 (UTC)

Reflection and refraction are not the same process, even though under certain circumstances they may produce simular results. Stating "reflection by refraction" is somewhat simular to stating "driving by bicycling" (I realize this is not a perfect comparison). Both driving and bicycling involve the movement of an operator via a vehicle, but they are otherwise very different processes. Like-wise reflection does not occur by refraction, or vice-versa. The following except is from: "Chapter 22: Radio Frequencies and Propagation". The ARRL Handbook for Radio Amateurs 1994 (71 ed.). The American Radio Relay League. 1993. pp. 22-1–22-2. ISBN 0-87259-171-9.

"Reflection and refraction are two words that often seem to be used interchangeably, even though they describe quite different phenomena. Reflection occurs at any boundary between materials with different dielectric constants. ... Refraction is the bending of a wave as it passes from one medium into another. ... Most amateur communication on the HF bands depends on this bending of radio waves, so it is a very important concept. ... On frequencies below 30 MHz, long distance communication is the result of refraction (bending) of the wave in the ionosphere."

Even further reading of techinical literature supports that reflection is not the process by which most long distance shortwave communications occurs. –Sparkgap (talk) 20:05, 2 September 2011 (UTC)

Since there is a more technical article available for those who want to read more, I don't object to using less technical language like "bending" rather than "refraction". But we should avoid incorrect language such as "reflection" so as not to point our readers in the wrong direction.

Also, in answer to "Why does HCJB come in on the same frequency that they announce?", the frequency is the same at the transmitter and receiver, so long as the transmitter, receiver, and intervening ionized regions are all stationary with respect to each other. But if the speed of propagation of the electromagnetic radiation is different at the transmitter and receiver (say, the receiver is on a high-altitude balloon), the wavelength will be different at the transmitter and receiver. Jc3s5h (talk) 20:25, 2 September 2011 (UTC)

Thenn we should say "bending" and not use more scientific-sounding jargon. Oh well, at least we don't have "backscatter" any more. --Wtshymanski (talk) 20:42, 2 September 2011 (UTC)

Advantages

I'm pretty sure that the bit about being able to detect the number of HF listeners via the EM of the circuits is not feasible. Haven't found any mention online or in any other source. — Preceding unsigned comment added by 67.233.139.238 (talk) 02:14, 9 February 2012 (UTC)

As far as I know this is quite feasible, because it was this emission that led n to the discovery of the Superheterodyne receiver. CodeCat (talk) 00:50, 10 February 2012 (UTC)

I doubt they can detect the "number of HF listeners" over long distances, but they can certainly drive down your street with a monitoring antenna and pick up the signal emitted from your radio. I think CodeCat is essentially right, because the way a Superhet receiver works is that a "local oscillator" (LO) radiates EM radio waves at a frequency that equals the tuning frequency plus (or minus) the "intermediate frequency" (IF). I've seen a first-hand demonstration this sort of spying done on an FM radio on the 88-108 MHz band. Knowing that the intermediate frequency of most FM radios is 10.7 MHz, if they detect a signal in the vicinity of your radio at 118.7 MHz (or 97.3 MHz, I forget whether the LO is offset above or below), then they know you're tuned in to 108 MHz. This technique relies on some standardization of the IF, e.g. 10.7 MHz in North America.

It also might be possible to spy on people by detecting the IF signal, which unlike the LO, contains the broadcast data. This signal can then be matched up to all the possible stations that you could be listening to.

To minimize this radiated signal would require shielding the LO and IF stages by wrapping them in conductive foil and grounding the foil, and possibly using additional filtering, both of which would make it more similar to a direct conversion receiver. --Mikiemike (talk) 03:23, 16 June 2012 (UTC)

new photo

Shortwave Radio Dial

may i point your interest to this photo? i took it today for the german article about shortwave. maybe you find it suitable for the opening section. i wanted to focus on shortwave, not on a universal radio receiver like the one in the intro of this article. Maximilian (talk) 23:28, 19 April 2012 (UTC)

I think a properly focused photo is better than the blurry one in the article now. Perhaps you could take another photo with a centimetre scale in it so people will know how big it is? Jc3s5h (talk) 23:37, 19 April 2012 (UTC)

the blurry photo in the article seems to show a LW/MW/SW receiver. if this is the case, it's a misleading picture for the article. my photo shows the ca. 3 cm wide display of a portable sony ICF-7600. a centimetre scale is, imho, not necessary for this photo and its message. the message is: we're tuning into 15 m band shortwave, bingo! Maximilian (talk) 23:23, 23 April 2012 (UTC)