Isn't the estimate that something like 90% of all wireless mics are being used by folks who technically never had the authorization to use the spectrum (...that is used...) is the first place? Something like how only radio and TV stations had the authority to use the standard wireless mic frequencies, but these days anyone doing professional sound for theater, sporting events, etc. is also using those same frequencies?
Maybe... when it's new, of the right type (e.g. tubular), clean, dry, and carefully installed.
My understanding is that the performance of 300-ohm twinlead installations tends to deteriorate significantly after a few years (sunlight and ozone attacks the twinlead, and dirt and pollution builds up) and during wet weather.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Last time I used twinlead, except for fiddling around, was on the family TV antenna installation using an Allied Radio Corodized VHF antenna, with Beldon Super Permaohm 300 ohm shielded twinlead. Good stuff.
greg
The only "evidence" I have is a "testimonial" by the guy who invented it, on some PBS show. And they claimed that that's how they pack so much antenna into a box the size of your thumb. ;-)
And, having a passing familiarity with fractals, it just sounds eminently plausible to me. :-)
Cheers! Rich
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?Their advertising budget suggest that they are getting sales and they do radiate to the satisfaction of their users They don't have lumped loads so where ';s the beef? Art
Where I'm sitting here in Whittier, KABC 7 is so strong I can get it without even a cable plugged in!
It's 50, 56, and 58 I worry about; 2-13 and 28 are covered; I'm looking forward to seeing if my new bowtie (from that youtube video, but with ER708-2 x 1/16 filler rod) will pick up PAX on 30. They have some nice oldies sometimes. (I also have some of the ER708-2 in 0.045".)
I'm gonna solder it together and hold it to the board with brass thumb- tacks. ;-)
Just for reference:
Cheers! Rich
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It's a folded, folded, folded, folded, folded,... n(folded) unipole antenna!! ;-)
Decent power, line of sight (18.2 miles @ 172.2 deg true) will do that. Check your email....
-mpm
Art:
I am ready to bend over backwards, until I can say different ...
However, how much you wanna' pay me for one of these?
--- | |
Ahah! Presently they don't. A big issue for opponents of 8VSB modulation was poor performance in mobile/handheld (M/H) applications. Straight 8VSB does not handle "dynamic multipath" well.
However ...
Development of the ATSC-M/H Standard for mobile and handheld applications is moving forward at a rapid pace. A critical element of that effort is the Independent Demonstration of Viability (IDOV). The goal of IDOV is to ensure that the technical proposals under consideration can meet the goal of enabling mobile and handheld services in early
2009.per
I read some news accounts of supposed successful tests (the "IDOV" ?) this past spring. We'll see.
BTW, alt.video.digital-tv newsgroup is doing a good job with the TV transition. Also,
The FCC and the TV broadcasters looked the other way because there is no evidence that such activity has ever caused any interference. I can get
6 microphones to work in an occupied analog TV channel and neither notices the other.The TV Band Devices the FCC has recently begun the process of authorizing are way more damaging than a 50 mW 65 kHz deviation FM signal.
Luckily, these devices will not be allowed anywhere near where I work. The FCC has banned them from the 13 biggest cities, and from within a kilometer of a venue or stadium using wireless microphones. The proposed rules do not require a Part 74 license for these protections.
Ion TV 30 is in Claremont and has a 3.8 Megawatt Signal (elliptically polarized no less). It should give you a tan in Whittier.
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interesting paper..
The big benefit (from a cursory reading).. is that you have a more consistent antenna pattern over the frequency range, which the vanilla bowtie does not. And a somewhat wider match bandwidth. (mostly extending it to higher frequencies)
Nothing magic, though.
There is apparently a "big benefit" for some applications contrary to the nay-sayers on this newsgroup. Apparently, the self-symmetry of fractals leads to some predictability as far as wide-band response goes.
Don't remember anyone saying that fractals were magic. They certainly obey Maxwell's laws. I suspect their advantages, like their straight-wire cousins, lie in the predictability of their mathematical models.
-- 73, Cecil http://www.w5dxp.com
As opposed to randomly trying other shapes, I guess..
So fractals fit in the "handy design approach" category
I dare say the Yea-sayers cannot predict any specific, practical, fractal characteristic when given fractal
For the inverse (starting with the practical instead of the mathematical model) one very simple test: give the mathematical model for a single fractal antenna specifically resonant on each frequency: 1.85MHz; 3.8MHz; 7.15MHz; 10.13MHz; 14.15MHz; 18.11MHz; 21.2MHz; 24.93MHz; 28.5MHz, to within the margins of any Ham band represented by the single frequency offered.
Solution: Biconical; LPDA (barring, of course, no one can give the fractal mathematical models). Of course, the joke here is that these are neither very gainful, nor small - the presumed boon of fractal invention. Yet no other "fractal" can describe this antenna above. Those "fractals" that come close (maybe covering 3 of the 9 bands) aren't small or gainful either. Sometimes you just can't win for trying either.
Going to specifics, what is the mathematical model (not just a word salad description) for a Sierpinksi Gasket? Using that mathematical model (what students call plug-n-chug for solving an equation), show the free space best gain at its sixth iteration, fourth resonance (the
30M band of the description above).What is the greatest physical dimension of this 9 band antenna? What would be its greatest physical dimension if implemented in a fourth iteration Triadic Cantor (if, in fact, one were possible to support these resonances)?
So, a specific fractal antenna, a specific implementation, a specific characteristic - and years before anyone here will offer a demonstration of -dare I say it?- predictability. Hasn't happened from any other correspondents here to this board in the entire history of the topic. In that same history, not one other scribbler has offered a link to someone who can do their work for them.
Fractals, always amusing.
Fractal design may prove as good of a way of shrinking an antenna as any other. Its just pure BS to think it is going to let you make a smaller antenna with the same gain as the full size antenna it was derived from. It is Mega BS to think that you are going to shrink the antenna and achive gain because of anything the fractals will contribute.
Jimmie
Since fractal antennas are finding practical applications when etched on a PC board, your discussion is about as moot at a 160m rotatable Yagi proving that rotatable Yagis are not feasible.
-- 73, Cecil http://www.w5dxp.com
Like I said - nothing predictable, no math model, etc. etc. etc.
Imagine, an antenna on a PC board - the miracle of the 3rd Millennium!
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