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!

Clarification:

216 MHz is what we're using now. We're getting away from 215 because of
interference with digital TV.

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

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!

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

On Thu, 20 Mar 2008 23:52:07 -0400, wrote:

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

Rumor has it that this antenna will be in the next ARRL Antenna
Handbook. Our club had an antenna party here recently where we built a
bunch of these. I chose to not glue mine together so it will store in
a very small package. You can also leave off elements at will to
reduce the physical size if needed.

Unfortunately, recent knee replacement has left me sidelined for a
while.

John Ferrell W8CCW
Beware of the dopeler effect (pronounced dope-ler).
That's where bad ideas seem good if they come at you
fast enough.

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.

"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.

"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.

"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