Bicycle frame as antenna?
 

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?

Bicycle frame as antenna?
 

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

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

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.

Bicycle frame as antenna?
 

wrote:
- Will the frame perform as an adequate antenna?

What would you use for the counterpoise?
--
73, Cecil http://www.w5dxp.com

Bicycle frame as antenna?
 

On 25 jul, 20:23, " 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?


Hello,

When you mean "AM broadcast band" with AM, you will very likely not
get it working. You will not be able to make a concealed efficient
antenna and noise level is that high, that you will never receive the
signal at one mile distance.

The antenna is the (most) difficult part. I would recommend you to go
to VHF (as Richard suggested). You can use the bicycle frame as ground
(counterpoise). You could insulate some metallic parts of the bicycle
(Rack, Fender, mudguard) and use that as an antenna. Make sure that
you don't compromise safety when modifying bicycles. The antenna
impedance will be reasonable so you can probably use a simple matching
network.

Because of the short(er) wavelength you can have some directivity in
the receiving antenna also, this helps to trace your "bait". "Bait-
bicycles" are frequently used by the Police.

When this is a non-commercial project, you may seek advice from the
Radio Amateur Community (in fact you did via this posting). Also don't
forget the legal aspects of radio frequency use.

Best regards,

Wim
PA3DJS
www.tetech.nl
the mail is OK when you remove abc

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

Bicycle frame as antenna?
 

Bicycle frame as antenna?
 

Wimpie wrote:

...
The antenna is the (most) difficult part. I would recommend you to go
to VHF (as Richard suggested). You can use the bicycle frame as ground
...
Best regards,

Wim
PA3DJS
www.tetech.nl
the mail is OK when you remove abc


I concur, perhaps a cheap FM xmitter in the range of 88-108mc. The
frame should serve as a good 1/2 wave antenna for this frequency and the
plans for such an xmitter are readily available--a search of the net
will provide you with multiple options ...

Regards,
JS

Bicycle frame as antenna?
 

Another solution could be APRS or something similar. There are
separate transmitters small enough to fit in a 1.5 - 2.0" tube,
encluding a battery. Antenna(s) in the seat, frame as the
counterpoise? RF burns? Oh, yeah, sure. But who cares, right? All
normal stipulations apply.
- 'Doc

Bicycle frame as antenna?
 

In message
,
writes


Another solution could be APRS or something similar. There are
separate transmitters small enough to fit in a 1.5 - 2.0" tube,
encluding a battery. Antenna(s) in the seat, frame as the
counterpoise? RF burns? Oh, yeah, sure. But who cares, right? All
normal stipulations apply.
- 'Doc

The frame itself may resonate on - or around - 2m (a fullwave, end to
end?). Maybe you can tap into it using a gamma-match.
--
Ian

Bicycle frame as antenna?
 

I'd like to set up a "bait-bike"
Cell phone left on, under the seat.
When missing, call the cops and give them the phone number to track.

Bicycle frame as antenna?
 

Richard Clark wrote:
I'd like to set up a "bait-bike"
Cell phone left on, under the seat.
When missing, call the cops and give them the phone number to track.

In my area, keeping a bicycle has always been difficult. Reporting a
bicycle theft to the police provoked a response from them, similar to,
"We probably won't find it."

Of course, stolen autos/motorcycles provoke a similar response. One is
left with the opinion they have much better things to do ... like
enforcing the laws which actually generate revenue for the
city/county/state ...

The chain and lock I now carry in a bag on my bike weighs more than the
bike itself ... some in my bike group first laughed. Now those who
laughed, who still have a bike, carry something similar.

Heck, maybe I am fighting an uphill battle--perhaps "they" are
right--and the wife and I don't need a bike. :-(

Anyway, I digress, I like your idea--but, what about a 1/2 pound of C4
under the seat, instead? evil grin

Regards,
JS

Bicycle frame as antenna?
 

John Smith wrote:
In my area, keeping a bicycle has always been difficult. Reporting a
bicycle theft to the police provoked a response from them, similar to,
"We probably won't find it."

I even recognized the thief who stole my bicycle.
The police refused to do anything because the thief
told them that he had "borrowed" it and returned it
by leaving it on my porch that same night and he
didn't know what happened to it after that.
--
73, Cecil http://www.w5dxp.com

Bicycle frame as antenna?
 

Cecil Moore wrote:
John Smith wrote:
In my area, keeping a bicycle has always been difficult. Reporting a
bicycle theft to the police provoked a response from them, similar to,
"We probably won't find it."

I even recognized the thief who stole my bicycle.
The police refused to do anything because the thief
told them that he had "borrowed" it and returned it
by leaving it on my porch that same night and he
didn't know what happened to it after that.

I am afraid, my response to "the cops", may have been along the lines:
"Oh YEAH! What was I ever thinking? That happens to me AND the
neighbors all the time!"

Laughing-To-Keep-From-Crying :-|

Regards,
JS

Bicycle frame as antenna?
 

Cecil Moore wrote:

John Smith wrote:
In my area, keeping a bicycle has always been difficult. Reporting a
bicycle theft to the police provoked a response from them, similar to,
"We probably won't find it."

I even recognized the thief who stole my bicycle.
The police refused to do anything because the thief
told them that he had "borrowed" it and returned it
by leaving it on my porch that same night and he
didn't know what happened to it after that.

Take 'em to small claims court?
--
(Robert Smits, Ladysmith BC)

"I'm not one of those who think Bill Gates is the devil. I simply suspect
that if Microsoft ever met up with the devil, it wouldn't need an
interpreter." - Nicholas Petreley

Bicycle frame as antenna?
 

Robert Smits wrote:
Take 'em to small claims court?

Take a homeless meth addict, who begs for money
door to door, to court? Shirley, you jest.
--
73, Cecil http://www.w5dxp.com

Bicycle frame as antenna?
 

Cecil Moore wrote:

Robert Smits wrote:
Take 'em to small claims court?

Take a homeless meth addict, who begs for money
door to door, to court? Shirley, you jest.

I wouldn't either, but that part wasn't mentioned before.

Bob

--
(Robert Smits, VE7HS, Ladysmith BC)

"I'm not one of those who think Bill Gates is the devil. I simply suspect
that if Microsoft ever met up with the devil, it wouldn't need an
interpreter." - Nicholas Petreley