RadioBanter - View Single Post

John Smith · July 26th 08, 11:03 AM posted to rec.radio.amateur.antenna

wrote:
We've been having trouble with bicycle thieves in my neighborhood. I'd
like to set up a "bait-bike" that includes a low-power pulse beacon AM
transmitter inside the frame and ***no visible*** antenna outside the
frame. I'd like to have approximately 1-mile range. I've built a
couple of Ramsey kits, but don't have much expertise.
- I'd appreciate any recommendations for a transmitter circuit.
- Will the frame perform as an adequate antenna?
- How about a dipole made from insulated wire taped to the exterior of
the frame?

You would need an LC (inductance/capacitance) loading circuit to
resonate the frame as a 1/2 wave "antenna" before it would even be
possible to work (heck, I have never really thought about it before, but
resonating it, the frame, at a full wavelength might even be better!)

I have actually heard of people, successfully, using a 1/2 radiator with
no counterpoise--with good results. In your idea/plan, this might just
be the best go ...

A mile range? That would require power which might be difficult to
provide with batteries and for an extended length of time ... where
would you hide those batteries? In the handlebars?

Regards,
JS