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Bicycle frame as antenna?
Richard Clark wrote:
On Fri, 25 Jul 2008 11:23:55 -0700 (PDT), " 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? No. - How about a dipole made from insulated wire taped to the exterior of the frame? Equally unlikely. If you have built Ramsey kits for AM transmitters, you should be well aware that they rarely transmit more than a block for the suggested, large (relatively speaking, of course) antenna. Putting something smaller, inside the frame is like trying to yell through a straw. Look for an FM transmitter kit. The antenna can be the frame and a wire wrapped around what looks like one of those kid's fiberglass whips for a flag. The whip only has to be a meter long at most. 73's Richard Clark, KB7QHC Alternatively, Petco has an electric fence kit that could be attached to the frame. :-) ac6xg |
#2
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Bicycle frame as antenna?
Jim Kelley wrote:
Richard Clark wrote: On Fri, 25 Jul 2008 11:23:55 -0700 (PDT), " 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? No. - How about a dipole made from insulated wire taped to the exterior of the frame? Equally unlikely. If you have built Ramsey kits for AM transmitters, you should be well aware that they rarely transmit more than a block for the suggested, large (relatively speaking, of course) antenna. Putting something smaller, inside the frame is like trying to yell through a straw. Look for an FM transmitter kit. The antenna can be the frame and a wire wrapped around what looks like one of those kid's fiberglass whips for a flag. The whip only has to be a meter long at most. 73's Richard Clark, KB7QHC Alternatively, Petco has an electric fence kit that could be attached to the frame. :-) ac6xg Put gentian violet powder on the hand grips, then look for purple hands on the thieves. |
#3
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Bicycle frame as antenna?
"Jim Kelley" wrote in message ... Richard Clark wrote: On Fri, 25 Jul 2008 11:23:55 -0700 (PDT), " 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? No. - How about a dipole made from insulated wire taped to the exterior of the frame? Equally unlikely. If you have built Ramsey kits for AM transmitters, you should be well aware that they rarely transmit more than a block for the suggested, large (relatively speaking, of course) antenna. Putting something smaller, inside the frame is like trying to yell through a straw. Look for an FM transmitter kit. The antenna can be the frame and a wire wrapped around what looks like one of those kid's fiberglass whips for a flag. The whip only has to be a meter long at most. 73's Richard Clark, KB7QHC Alternatively, Petco has an electric fence kit that could be attached to the frame. :-) ac6xg You're a man after my own heart, ac6xg. 8) Jack |
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