View single post by Jeff
 Posted: Dec 5th, 2007 08:05 PM
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Jeff

 

Joined: Nov 7th, 2007
Location: Alabama USA
Posts: 127
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 Hi all!  Here's an update:  I'm awaiting the arrival of some high frequency patch cables.  These are RF patches that have BNC to BNC connectors on each end.  See below for an explanation of BNC.  I could easily make them myself, as I have plenty of RG-8X cable, but I am currently working on the transmitting antenna and Faraday enclosure.  The transmitting antenna and the Faraday enclosure are the toughest stage in the Spiricom system.  All, but the transmitting antenna, Faraday enclosure, and vocal synth are here; and working properly.

You're probably wondering about the receiving antenna.  Receiving antennas do not require resonation (impedance matching) nearly as close as a transmitting antenna, so I have that one figured out. 

To quickly review:  Antennas are a component of an electrical-magnetic resonant circuit.  Their size is a function of the frequency of the resonance, in our case 29.575 MHz.  A transmitter requires a certain load at its resonant frequency, usually 50 Ohms; but based on the RF generator or transmitter, the required load may be as high as 600 Ohms.  The transmitter antenna offers that load...if it is the correct length.  The antenna can be of a length of a harmonic of the fundamental (29.575 MHz) frequency.  In other words, the harmonic may be 20 times the fundamental (29.575*20)= 591.5 MHz.  The antenna can then be calculated on the 591.5 MHz frequency, making that antenna much shorter, but resonant, with supporting passive devices such as inductors and capacitors, and this isn't a problem.

So here's where I'm at:  I am creating a resonant antenna that does not require much space, and will be enclosed in a Faraday cage.  Fortunately, I am not broadcasting.  I don't need much power; nor do I need a full sized resonant antenna.  I only need to resonate at the specified frequency at this time.  If I need to resonate at a wider bandwidth, and I know I will in the not-so-distant future, then I will create a de-tuned antenna that will resonate, with small losses, over a larger bandwidth, say 20 MHz to 50 MHz.  Then, as we progress, a multiple antenna array can be created to cover a very large bandwidth, as Mark VI was originally designed:  30 MHz - 20 GHz, or more.  For now, these are baby steps, for good reason.  We must scientifically document our data; and procedures, just as the Metascience Foundation did. 

Please  offer your comments and questions!

BNC stands for Bayonet Neill-Concelman.  A short explanation, with pictures, can be seen here:
http://en.wikipedia.org/wiki/BNC_connector


Jeff