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commercially available, as are suitably sensitive receivers, so atmospheric attenuation shouldn't be a common limiting factor, except perhaps with homebrew or experimental equipment. I will agree that the statements are too general, especially for a complex area of propagation theory. I'll see if I can dig up a few sources for atmospheric and other path losses to help clarify this.
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In the US, the FCC is pretty flexible in what kinds of emissions stations in the amateur service may emit, as one of the service's purposes is to "contribute to the advancement of the radio art" (§97.1(b)). As far as station identification is concerned, there are some limitations, but a station does
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True, path loss due to atmospheric attenuation can be a factor at higher microwave frequencies, but at these frequencies it isn't usually more limiting than line-of-sight for communications links, except perhaps as you note at low power levels. Suitably high-power transmitters are pretty common and
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We could use a photo of an image transmitted by fast-scan ham TV, or photos of the equipment used (especially before it became an app on an iPhone). I found a "slow scan" image on
Commons but that's not what this article is about. Leaving the photo tag on, since a coule of test patterns don't tell
823:
In the 33 and 23 cm band sections, the propagation statements are dubious at best. I doubt a reliable citation to support the statements can be found; all the technical material I've seen for UHF and higher propagation indicates line-of-sight propagation at these frequencies except under unusual
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path, if all other factors are held equal (such as the antenna gains of the sender and receivers and the TX power, among other things), the path loss will increase with frequency, therefore the maximum distance a signal can be received will decrease when frequency is increased. (Keep in mind a
925:
Yes, in the context of ATV, the signals are quite weak. As I understand it, home-brew equipment is not uncommon for ATV, and transmitter power outputs in the range of 100 milliwatts to 5 watts appear to be the norm for most stations. Also to save on expenses, it appears common to not use
1077:
This is another area Radio
Amateur of televion transmission. I added some slow scan images to this article by mistake. This particular article relates to high definition, high quality FAST Scan transmissions. I am adding this comment in case anyone else makes the same mistake as I did
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Yes, I agree with such being a dubious comment, I have not heard anything myself, Part 97 or elsewhere, prohibiting the use of digital modes with amateur television. Amateur radio has always been a testing ground for newly-devised modes of communication on the airwaves (a la
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While the wording of these statements may not be the best, there is a truth behind them. I'm not so doubtful a reliable citation couldn't be found, as I've seen similar statements in the past. What is trying to be described is the effect of a frequency increase on
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they state, "... the 1200 MHz band goes 1/3 the distance of the 400 MHz band, and 2.4 GHz 1/6 given the same power and antenna gain..." This is a rather simplistic view on propagation, but I can understand why they state it the way they do, in an advertisement.
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I've made an edit which hopefully straightens out the bits about propagation and includes a bit of extra information with links to articles and reference. In a nutshell, I deleted the unsourced text I marked earlier, and added a paragraph in the (renamed)
761:! As far as non-commercial programming is concerned, I imagine as long as it's a program that's somewhat related to amateur radio and, most importantly, does not contain music of any kind (broadcasting of music on amateur radio bands is forbidden by the
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a signal.) What I do doubt in these statements is the nice, clean one-half and one-third reductions in distance. I suspect these are very rounded numbers, made just to simplify the description of the effect. A citation from a
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About digital amateur television in the USA -- where exactly in Part 97 does it specifically state that digital image modes are prohibited? As far as I've found it's LEGAL. Until a citation is given, I dispute this sentence.
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Chapter 20 of the 1991 ARRL Handbook says that path losses are higher at 24 cm compared to 70 cm, but that is partially compensated by being able to put more antenna elements on the same length of boom.
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About broadcasting non-commercial programming -- where exactly in Part 97 is this allowed for? As far as I've found, it is ILLEGAL. Until a citation is given, I dispute this sentence.
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You're right, this article is in need of clean up. I put the clean-up tag on. Those fact need to be cleared up, and also the article itself needs some general work all around.
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I can't find any limitation or specification of what kind of television transmission standard can be used in the amateur service, other than
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section describing some factors which affect propagation. The source citeed is the 2005 edition of the ARRL Handbook. How does this look?
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technology, organizations, and activities. If you would like to participate, you can edit the article attached to this page, or visit the
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not have to identify in the same emission as they are sending information in. Anyway, I would not recommend adding the statements.
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make a pretty substantial difference when you're talking about a 6 MHz or so AM channel instead of a 200 KHz or so FM channel.
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coverage from them over their ATV stations/repeaters, and NASA TV is non-commercial, considering NASA is a US Gov't agency.
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circumstances, but the way this is worded seems to make it difficult to dispute without original research.
679:"when all or part of the communications are transmitted in the same image emission". §73.682(a) describes
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as commonly available at substantial power levels. I'll try to keep that in mind, as it
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765:) or convey any commercial message or call to action, it should be ok. Case in point--
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I also just reminded myself that this is in the context of ATV, where equipment isn't
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filters, if one can reasonably get away with it. That effectively increases the ATV
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Looks alright. I could see a potential expansion of the section in the future. –
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and such), so it seems preposterous to say that digital video, whether
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which authorizes station identification in an image mode conforming to
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853:receiver has a minimum signal strength needed to
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516:VE7APU (developed the Terminal node controller)
257:International Lighthouse and Lightship Weekend
461:New Zealand Association of Radio Transmitters
349:Federacion Mexicana de Radio Experimentadores
103:, which collaborates on articles related to
1132:Knowledge requested images of amateur radio
284:Salvation Army Team Emergency Radio Network
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573:Wireless Institute Civil Emergency Network
638:may be able to locate suitable images on
363:- published in the USA from 1968 to 1990
962:After a little searching, I found that
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769:. Thousands of ATV hams re-broadcast
476:amateur radio emergency communications
538:- JA3FA, founder of Icom Incorporated
212:Amateur radio international operation
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504:, but on ionosphere, not troposphere
95:This article is within the scope of
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520:Mirage (manufacturer)
1073:Slow-scan television
642:and other web sites.
564:into its own article
558:Tropospheric ducting
554:for a starting point
400:The Canadian Amateur
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360:Ham radio (magazine)
314:VHF/UHF Century Club
1098:the reader much. --
862:source is needed.
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468:- SDR maker
165:Improve to
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30:Start-class
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1078:yesterday.
860:verifiable
855:demodulate
677:§73.682(a)
621:photograph
568:Vectronics
488:DX cluster
190:Morse code
113:discussion
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883:Pyrocatch
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846:Path loss
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450:Ameritron
207:20 meters
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864:Sparkgap
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625:included
562:TV-FM DX
552:TV-FM DX
354:Gin pole
279:Replexer
968:catalog
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426:Create:
324:Winlink
299:Skywarn
267:Hy-Gain
169:-Class:
145:on the
723:Kc8ryw
663:Kc8ryw
649:Upload
640:Flickr
550:- see
472:HAMNET
273:Radcom
36:scale.
897:quite
755:DVB-T
747:PSK31
482:HB9CV
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137:High
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