Talk:Longwave
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[edit] Royal Navy subs
...monitoring 198 kHz. This claim, I think, needs qualifying with an "allegedly" or two. See The Today programme. Don't know -- seems to me like an adroit terrorist group could provoke a nuclear holocaust simply by taking out Droitwich (or Daventry?). –Hajor 20:41, 18 May 2004 (UTC)
- I am also sceptical of the usefulness of this approach during peacetime, because subs have two-way VLF radio communication. In a crisis, when subs need to maintain complete radio silence, the British authorities could set up military exclusion zones around the three transmitters (Droitwich, Burghead and Westerglen) and such an approach might be more likely. (I suspect Burghead and Westerglen would be switched off in such a situation - subs probably have better receivers than the average Scottish household!). Rugxulo 22:11, 19 January 2006 (UTC)
[edit] Canada
I don't know that Industry Canada has allowed "LowFER" in Canada - can anyone find a cite for this? I'll have to check the IC Web site, maybe it's there...--Wtshymanski 13:32, 3 Jun 2005 (UTC)
[edit] Defunct long wave broadcasts?
I seem to recall reading an old issue of Practical Wireless from the 1970s which listed long wave broadcasts from Central Asia that were well into the 300's of kHz. Did these broadcasts exist? If anyone has firm information it would be an interesting addition to the article. Rugxulo 22:11, 19 January 2006 (UTC)
[edit] In light of this article,
http://www.eurekalert.org/pub_releases/2006-02/su-rgf021706.php someone might want to re-evaluate the statement in the first paragraph of this article about how "longwave signals do not reflect or refract using the ionosphere."
The linked article says "Scientists detect these localized disturbances with VLF radio waves propagating along the Earth's surface. The ionosphere, like a metal, is a good electrical conductor. It acts as a guide for radio waves. That's why the Earth's curvature is no barrier, as VLF radio waves bounce off the ionosphere and can propagate to long distances around the globe, in the so-called Earth-ionosphere wave guide."
I realize that most lowfer xmissions use groundwave prop, but why would signals longer in wavelength than HF not also reflect from the ionosphere?
[edit] Relation to LF and MF articles
I've attempted to clarify the relationship between this article, and the LF and MF articles. The situation is still not very good, however; for example, information on longwave amateur bands is in LF, whereas information on LF commercial stations is in longwave. Some kind of merger seems to be in order, but I don't know the best way to handle that, given that the bands don't exactly match. — Johan the Ghost seance 10:25, 11 May 2006 (UTC)
- Now general information about LF (30-300 kHz) is in Low frequency and information specifically about LF broadcasting is in Longwave. Sv1xv (talk) 18:46, 1 March 2008 (UTC)
[edit] Clarkestown at night
This article claims that RTÉ off Clarkestown decreases its power at night. Now, as far as I can tell and remember (I live fairly close to the mast), in its Atlantic 252 days, Clarkestown operated 100kW daytime and 500kW nighttime. The station engineer I talked to also said the Radio Algeria transmitter went off-air over night. Obviously, even at the suggested power here, I'm not gonna be able to check the Radio Algeria transmissions without some very, very impressive sheilding :p There were reports back in the early 1990s of it being received in Brazil at night, which would suggest it had a clear channel.
Also, I've since been told that RTÉ now operate it at max. 300kW for simple cost saving reasons - they don't need a music quality signal across the entire UK; however would have thought that its still 100 day, 300 night. The site can actually operate at 600 but has no ITU clearance for such. --Kiand 03:12, 27 June 2006 (UTC)
The Irish allocation is for 500Kw daytime and 100 Kw night (Clarkestown can theoretically operate at 600Kw but as far as Im aware never actually has). The reason for this is that Longwave (and Mediumwave) signals travel further distances at night (due to ionospheric reflections) leading to increaced interference problems with other countries. In order to mitigate this (somewhat) it is common practive (particularly for larger stations) to run on reduced power at night.
During the odd breakdown at Clarkestown Algeria makes it quite well into Ireland (especially along the South coast) many people mistake it for a French station (since Algeria has two official languages French and Arabic) Finland also has an allocation for 1500Kw on 252 but has never used any more than 100Kw and in recent years hasnt used it at all. 87.112.28.7 13:22, 4 March 2007 (UTC)
[edit] 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).
[edit] Longwave simulcasts in the US
I've heard numerous AM stations simulcast in the LW band inside the US. This seems to contradict the claim that there is no LW broadcast band.
- A very late reply to that August 2007 comment but please amplify. It's possible what you're hearing is an image of a normal AM broadcast band transmitter; if you notice a consistent pattern where local AM transmitters show up 455 kHz lower on your LF receiver, I suspect this is the case. Other, more complex sources of images can occur especially if two or more transmitters produce a difference frequency in the LF band - but then you'd hear both of them interfering. A good check on this is to put a low-pass filter between the antenna and receiver; even a few extra dB of rejection of the AM broadcast band may make the images go away. --Wtshymanski (talk) 18:55, 1 March 2008 (UTC)
[edit] Band Propagation
Article says: Instead, the D-layer of the ionosphere and the surface of the earth serve as a waveguide directing the signal[citation needed].
The following page describes in verbal and graphic way how the ionosphere and the earth's surface act as waveguides for longwave transmissions. http://www.weather.nps.navy.mil/~psguest/EMEO_online/module2/module_2_6.html
I am not sure if it's valid as a citation hence adding it here. I searched elsewhere with little success as how the ionosphere affects longwave radiation.
193.120.148.177 (talk) 20:47, 21 March 2008 (UTC)
