Directional antenna in the 215 to 218 MHz band
Hi Folks:
I'm looking to make a directional antenna in the 215 to 218 MHz band (215 if that's too broad), used for location of dementia patients who have wandered away from their caregivers. I'm a volunteer with an organization that locates these people. They wear a tiny transmitter which emits a chirp that can be heard from 1-2 miles on the ground and 8-10 miles via helicopter. I'm somewhat new to the program, and I'd like to do some investigation on my own regarding antenna types that would be useful, and I hope you'll all grant me a few questions. My needs are this.... the antenna must be as directional as possible. It must be most efficient in the 215 to 218 MHz band 215 is what our patients are on right now, though after we fill up that range we have licensed through 218 MHz. It must be easy for an individual to carry, and portable enough to carry through any type of terrain. It must be shaped in such a way that it's relatively safe and easy to use in an enclosed area, either in a helicopter or a car. Currently the agency is using a 4 element Yagi, which works well, but has the drawback of being a real eye-poker when used in close quarters, and in fact the California Highway Patrol will not allow them to be used in their helicopters because of that reason. One of our Search & Rescue guys built his own 4 element Quad Yagi out of some 1/2" PVC pipe and other parts that are readily available at any Home Depot. It has greater sensitivity than our stock antenna, and the CHP has said that it's OK to use in their helicopters. Rather than 4 horizontal straight beams it has 4 squarish beams, with no points to poke people's eyes out. I'm still waiting to get the plans from him for that antenna, and I though that in the meantime I'd ask in here if any of you had some interesting leads for me to follow. Many thanks! |
Directional antenna in the 215 to 218 MHz band
Clarification:
216 MHz is what we're using now. We're getting away from 215 because of interference with digital TV. |
Directional antenna in the 215 to 218 MHz band
On Thu, 20 Mar 2008 05:44:50 GMT, "usmcbrat"
wrote: My needs are this.... the antenna must be as directional as possible. It must be most efficient in the 215 to 218 MHz band 215 is what our patients are on right now, though after we fill up that range we have licensed through 218 MHz. It must be easy for an individual to carry, and portable enough to carry through any type of terrain. It must be shaped in such a way that it's relatively safe and easy to use in an enclosed area, either in a helicopter or a car. Currently the agency is using a 4 element Yagi, which works well, but has the drawback of being a real eye-poker when used in close quarters, and in fact the California Highway Patrol will not allow them to be used in their helicopters because of that reason. Hi USMCbrat, Research the Google newsgroups (for this newsgroup specifically) archive with the keyword "foxhunt." There are more issues than just directionality to be considered. ARMYbrat Richard Clark, KB7QHC |
Directional antenna in the 215 to 218 MHz band
Do a search for "tape measure antenna". It is a simple to build yagi
antenna made of pvc pipe with elements made from a metal measuring tape. You can rescale it to your frequency. Kingfish On Thu, 20 Mar 2008 05:44:50 GMT, "usmcbrat" wrote: Hi Folks: I'm looking to make a directional antenna in the 215 to 218 MHz band (215 if that's too broad), used for location of dementia patients who have wandered away from their caregivers. I'm a volunteer with an organization that locates these people. They wear a tiny transmitter which emits a chirp that can be heard from 1-2 miles on the ground and 8-10 miles via helicopter. I'm somewhat new to the program, and I'd like to do some investigation on my own regarding antenna types that would be useful, and I hope you'll all grant me a few questions. My needs are this.... the antenna must be as directional as possible. It must be most efficient in the 215 to 218 MHz band 215 is what our patients are on right now, though after we fill up that range we have licensed through 218 MHz. It must be easy for an individual to carry, and portable enough to carry through any type of terrain. It must be shaped in such a way that it's relatively safe and easy to use in an enclosed area, either in a helicopter or a car. Currently the agency is using a 4 element Yagi, which works well, but has the drawback of being a real eye-poker when used in close quarters, and in fact the California Highway Patrol will not allow them to be used in their helicopters because of that reason. One of our Search & Rescue guys built his own 4 element Quad Yagi out of some 1/2" PVC pipe and other parts that are readily available at any Home Depot. It has greater sensitivity than our stock antenna, and the CHP has said that it's OK to use in their helicopters. Rather than 4 horizontal straight beams it has 4 squarish beams, with no points to poke people's eyes out. I'm still waiting to get the plans from him for that antenna, and I though that in the meantime I'd ask in here if any of you had some interesting leads for me to follow. Many thanks! |
Directional antenna in the 215 to 218 MHz band
I'm looking to make a directional antenna in the 215 to 218 MHz band (215 if that's too broad), used for location of dementia patients who have wandered away from their caregivers. I'm a volunteer with an organization that locates these people. They wear a tiny transmitter which emits a chirp that can be heard from 1-2 miles on the ground and 8-10 miles via helicopter. You might do a bit of research on the equipment that various animal tracking organizations use. They tend to use the 215 - 218 MHz band for tracking various animal species, and the equipment should suit your needs also. Ed K7AAT |
Directional antenna in the 215 to 218 MHz band
|
Directional antenna in the 215 to 218 MHz band
"Richard Clark" wrote in message Research the Google newsgroups (for this newsgroup specifically) archive with the keyword "foxhunt." There are more issues than just directionality to be considered. ARMYbrat Richard Clark, KB7QHC Thanks ARMYbrat. This USMCbrat appreciates it, and everything else! :) Most of what I've found thus far is about the same as what we're currently using, which is a flat 4 element Yagi. I may not be versed enough to describe the plans I'm looking for, but when I find them I'll post here. The antenna I'm looking for is perhaps better described as a 4 element Box or Cube Yagi where the frame is built of 1/2 inch PCV and the elements are fairly heavy guage wire. There's no sharp points to hurt someone's eye, which is frowned upon by the California Highway Patrol for use in their helicopters. There's a guy that I trained with who has the plans and hasn't yet gotten back to me with them, but I'll be persistent and let people here know when I get the plans. |
Directional antenna in the 215 to 218 MHz band
wrote in message
... Do a search for "tape measure antenna". It is a simple to build yagi antenna made of pvc pipe with elements made from a metal measuring tape. You can rescale it to your frequency. Kingfish Thanks Kingfish. That's pretty cool! It's actually much like what we're using now... A 4 element Yagi, though ours don't have the flexible elements like one made of tape measure. |
Directional antenna in the 215 to 218 MHz band
"Ed_G" wrote in message You might do a bit of research on the equipment that various animal tracking organizations use. They tend to use the 215 - 218 MHz band for tracking various animal species, and the equipment should suit your needs also. Thanks Ed. That's a good idea, and you're exactly right... what we're doing looks just like what you'd see on a television nature show where someone had a radio collar on a lion or something like that. We're applying the same technology to Alzheimer's patients who are at risk of wandering. |
Directional antenna in the 215 to 218 MHz band
"usmcbrat" wrote in message news:5_cFj.257$rb6.143@trnddc01... "Richard Clark" wrote in message Research the Google newsgroups (for this newsgroup specifically) archive with the keyword "foxhunt." There are more issues than just directionality to be considered. ARMYbrat Richard Clark, KB7QHC Thanks ARMYbrat. This USMCbrat appreciates it, and everything else! :) Most of what I've found thus far is about the same as what we're currently using, which is a flat 4 element Yagi. I may not be versed enough to describe the plans I'm looking for, but when I find them I'll post here. The antenna I'm looking for is perhaps better described as a 4 element Box or Cube Yagi where the frame is built of 1/2 inch PCV and the elements are fairly heavy guage wire. There's no sharp points to hurt someone's eye, which is frowned upon by the California Highway Patrol for use in their helicopters. There's a guy that I trained with who has the plans and hasn't yet gotten back to me with them, but I'll be persistent and let people here know when I get the plans. Search Google with "cubical quad" and you'll find what you want, I think. There are even some calculators for this type antenna listed. http://en.wikipedia.org/wiki/Quad_antenna 73, John |
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