Topband: Extreme directivity

[Les Kalmus]

Ford,

You need to get a radio. You definitely need more to do : )

73, Les

Ford Peterson wrote:
> Once again you guys have proved to me that I should keep my day job and
> forget about my fascination for theoretical physics.  The SciAm article
> producing the inspiration was in the May 2007 issue, pg 96.  You can read
> all about the basic audio technology at www.holosonics.com
>
> Several respondents pointed out that a 432 signal modulated by 2 MHz would
> provide a nice 430 and 434 sideband in addition to the 432 carrier.  So my
> arithmetic was somewhat ill conceived.  A better analogy to the audio
> version would be to modulate the 432 with a 430 signal, producing a sideband
> of 2 MHz and 864 MHz.  Once again, the question being does the 2MHz spur
> form a wave front analogous to the 432 antenna's pattern or not.
>
> Keith-G3OIT points out that if it worked, why not use laser light to really
> form a tight beam?  Photons are photons after all.  I must retort that
> finding a light source stable enough to produce a 1.8MHz difference might be
> a bit difficult to construct.
>
> Rick-N6RK and Tom-W8JI (and others) point out that air is
> electromagnetically linear.  Non-linearity would have to be introduced.
>
> Dan-N3OX suggests that air can be made non-linear by turning up intensities.
> At RF you would have to use enough power to create a plasma.
>
> Harold-W0RI suggests that if there were non-linearity in air, then the
> spectrum would be filled with mixing products from all sorts of signals
> mixing.  However, I must retort that naturally occurring signals would all
> be arriving on different vectors and would not add or subtract in any
> meaningful way.
>
> A decent workshop could easily prove this out.  I'd do the experiment myself
> but my entire shack was destroyed by a lightning bolt last June.  I don't
> even own a working radio at the moment.  Needless to say I'm RF challenged
> at the moment.
>
> How about this?  Combine a stable 432 and a 434 signal--even a hybrid
> combiner would work.  Pump the pair of signals into a 432 yagi and listen to
> the 1.8MHz spur at some distance away.  Frankly, there is nothing magic
> about 432.  You could do the same experiment using any yagi--50MHz, 144MHz,
> etc, just use 2 signals 1.8MHz apart.  Rotate the source antenna while
> monitoring the signal strength of the 1.8MHz spur at some distance away.
> The pair of signals, separated by 1.8MHz, may possibly combine external to
> the antenna since they would be arriving at the detector on the same vector.
> Photons do add and cancel each other when they occupy the same space--there
> can be no denial of that.  The real issue is whether they will add and
> subtract in a way so as to produce a 1.8MHz envelope and a related wave
> front.
>
> Ford-N0FP
>
>
> _______________________________________________
> Topband mailing list
> Topband at contesting.com
> http://lists.contesting.com/mailman/listinfo/topband
>
>