I need to create an AM modulated carrier of 25 Khz that is highly
focused in beam width. I am aware of part 15 and will not be using
this for any other reason than for research. I need a range of 50
feet. Receiver will be a tuned resonant tank with about 90 db of gain
post detection. I would like to be able to "focus" this beam but being
in optics I have no idea of how one might control the dispersion of a
carrier like this. In other words in my field I can collimate or focus
a light beam but dealing with this wavelength I have not a clue!

Thank You in advance for your input

Steve Sands

Thanks for all the input. I did leave out an important fact. I did
intend to use a coil wound on a form or around a either a steel or
ferrite rod depending on efficiency. I have already done some tests
and projecting a detectable carrier is in the bag so to speak.
**********************************************
The
problem lies in shaping the dispersion so I can focus the beam into a
limited space, say 25 feet in diameter at 50 feet from the radiating
coil.
************************************************** ************
*** Yes - that is the problem - and it is unsurmountable for that frequency
at that range
************************************************** *****************
Sorry for the omission.
*********************************************
The omission makes no difference -
You will not be able to focus a beam at that distance using that frequency.
you will be able to detect the carrier - but if you walk around the
transmitter in a circle at that range with your detector (receiver), you
will notice that it was not a beam at all - the signal strength will not
vary as you might be expecting.
again - I would use a much higher frequency to experiment with.
- but what the heck - try it anyway - then you will see for yourself that
you should have used a higher frequency.


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