Talk:Spread spectrum
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[edit] Hedy Lamarr
Yes, Hedy (Not Headley) Lamarr the film star invented a rudimentary spread spectrum technology during world war II. Basically it was a a piano roll that controlled a radio tuner, forcing it to switch channels at regular intervals. Both sides of the conversation started the roll at the same time and then proceeded to talk normally. If you didn't have a copy of the roll, you would lose the conversation every couple of seconds and have to go find it again, which meant it was effectively impossible to eavesdrop. Here's a webpage about it: [1]. Here's some info about her patent: [http://inventors.about.com/library/inventors/bllamar.ht
[edit] Combining sections
The discussion in the history section seeems somewhat redundant with some of the "notes" in the next section.
Suggest we remove the redundancy, but didn't want to make so big a change without requesting views of others.
[edit] POV?
Note the following line: "(She learned about the problem after being forced to attend defence meetings with her ex-husband while she was in Germany prior to WWII)"
I can't see a source for this listed under the references in the article, so it seems to me like a simple and very out-of-place attempt to discredit Hedy Lamarr. So I removed it.
- Reference added, line modified and added back in. Why that statement would discredit her is beyond me.
- P.S. Please sign your posts. --QEDquid 17:44, 18 July 2006 (UTC)
[edit] SIGSALY
I am puzzled by the SIGSALY refernce in this article. When you read the SIGSALY article there is mention of a lot of pioneering innovations but none directly related to either frequency hopping or direct sequence. Suggest that someone either clarify the discussion of SIGSALY here and on its own article or else we remove this point.
On the other hand, I can see that SIGSALY may have been the first example of synchronizing pseudonoise generators at both ends of a communications link. (I suppose a pair of phonograph records with the same exact random noise would be in effect "pseudonoise" although others may disagree over the semantics.) Of course, spread spectrum today usually uses LFSR or cryptographically generated nonlinear PN - not one time pads on phonograph records.
[edit] Modulation?
Is Spread Spectrum a modulation technique?
That point is not clear in the article. In related articles (see CDMA), is pointed out that spread spectrum techniques can be used, and are used, for multiplexing purposes. In CDMA article is established that it is NOT a modulation technique. On the other hand, in this article, it is mentioned that "Ultra Wideband (UWB) is another modulation technique", suggesting that spread sprectrum is, as well, a modulation technique. Is it? —The preceding unsigned comment was added by 158.227.115.40 (talk) 09:02, 21 February 2007 (UTC). Acprisip 09:12, 21 February 2007 (UTC)
