On Sat, 02 Aug 2003 11:11:31 +0100, Paul Burridge hath writ:
Paul Burridge wrote:

Can anyone suggest a suitable material from which to make an
ultra-flexible mobile whip antenna say about 3 to 4 feet long. I need
something that can be bent to 90 degrees at a very small radius and
still return to reasonable straightness.

Yeah, sorry chaps, I should have better defined what I meant by 'very
small radius'. I compete in radio-controlled model battles, so the
model stands to get fipped upside down from time to time in a very
bruising environment and it already has a very low ground-clearance,
so using a spring as a base mounting won't help much, I'm afraid.
We're talking about radiuses of as little as 5mm! How about the
specific grade of stainless steel in wire form that springs are made
from? I know where I can get hold of some of that....

You might try a section from a steel tape measure.
(Just don't select one of the cheap, Made-In-China plastic/mylar
ones. HI!HI!)
Additionally, try to mount the antenna in a "well" on the robot.
Even a well of 5-10 mm will help out.

HTH,
Jonesy
--
| Marvin L Jones | jonz | W3DHJ | OS/2
| Gunnison, Colorado | @ | Jonesy | linux __
| 7,703' -- 2,345m | config.com | DM68mn SK

On 2 Aug 2003 16:24:24 GMT, Allodoxaphobia
wrote:

You might try a section from a steel tape measure.
(Just don't select one of the cheap, Made-In-China plastic/mylar
ones. HI!HI!)
Additionally, try to mount the antenna in a "well" on the robot.
Even a well of 5-10 mm will help out.

Not sure about the tape measure suggestion, but mounting in a well is
something I'd not considered and am most grateful for the idea of!
Thanks...
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill

"Paul Burridge" wrote in message
...
On 2 Aug 2003 16:24:24 GMT, Allodoxaphobia
wrote:

You might try a section from a steel tape measure.
(Just don't select one of the cheap, Made-In-China plastic/mylar
ones. HI!HI!)
Additionally, try to mount the antenna in a "well" on the robot.
Even a well of 5-10 mm will help out.

Not sure about the tape measure suggestion, but mounting in a well is
something I'd not considered and am most grateful for the idea of!
Thanks...

Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.

Is there anything in the rules forbidding your installing a jammer
transmitter to cause the other bot to lose its command channel? Probobly a
poor use of what little electrical capacity the onboard battery holds, but
it would be one way of causing the other bot to freeze in place and become
like a deer in the headlights.
thanks, John.
KC5DWD

On Sat, 2 Aug 2003 18:24:44 -0500, "john graesser"
wrote:

Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.

If I believed this idea was workable I'd have implemented it by now.
You need to bear in mind that immediately beneath the polycarbonate
surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..

Is there anything in the rules forbidding your installing a jammer
transmitter to cause the other bot to lose its command channel? Probobly a
poor use of what little electrical capacity the onboard battery holds,

There's a considerable amount of battery power on board, actually,
since the peak current draw is well over 100 Amps at times. A few
milliwatts for a local jammer would therefore be a negligable drain on
resources. *However* as you've already guessed, jammers are banned, as
are EMP pulse type weapons and such like. The reason for this is very
sound, when you think about it: it makes for really bad TV. The
producers want to see as much *action* as possible. You ain't gonna
get that if everybody's disabled everybody else's robot!
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill

surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..
I do not know the frequencies, but if they are high enough, one could think
of a slot or a patch antenna

Is there anything in the rules forbidding your installing a jammer
If jamming would be allowed, it would be a totally different sport (but
interesting as well). In that case you may as well omit the robots See all
the military history about ECM, ECCM, ECCCM (Electronic Counter(*n)
Measures) etc.

Wim

surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..
I do not know the frequencies, but if they are high enough, one could think
of a slot or a patch antenna

Is there anything in the rules forbidding your installing a jammer
If jamming would be allowed, it would be a totally different sport (but
interesting as well). In that case you may as well omit the robots See all
the military history about ECM, ECCM, ECCCM (Electronic Counter(*n)
Measures) etc.

Wim

Paul Burridge wrote:
On Sat, 2 Aug 2003 18:24:44 -0500, "john graesser"
wrote:


Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.


If I believed this idea was workable I'd have implemented it by now.
You need to bear in mind that immediately beneath the polycarbonate
surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..

Frequency limits prevent slot antennas in plate metal armor?

If so, loop antenna on top of the polycarb, with another
layer on top of that? You need a certain amount of standoff;
how much at your allowed frequencies? It'll amount to a box
or block of plastic stuck on the 'bot, but should be
relatively invulnerable.

Mark L. Fergerson

Paul Burridge wrote:
On Sat, 2 Aug 2003 18:24:44 -0500, "john graesser"
wrote:


Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.


If I believed this idea was workable I'd have implemented it by now.
You need to bear in mind that immediately beneath the polycarbonate
surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..

Frequency limits prevent slot antennas in plate metal armor?

If so, loop antenna on top of the polycarb, with another
layer on top of that? You need a certain amount of standoff;
how much at your allowed frequencies? It'll amount to a box
or block of plastic stuck on the 'bot, but should be
relatively invulnerable.

Mark L. Fergerson

On Sat, 2 Aug 2003 18:24:44 -0500, "john graesser"
wrote:

Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.

If I believed this idea was workable I'd have implemented it by now.
You need to bear in mind that immediately beneath the polycarbonate
surface armor, there's a hulking great metal framework. Consequently,
sandwiching the antenna between the armour and the frame is going to
lead to unacceptable loss of radiated energy, I'd have thought. Unless
anyone knows differently..

Is there anything in the rules forbidding your installing a jammer
transmitter to cause the other bot to lose its command channel? Probobly a
poor use of what little electrical capacity the onboard battery holds,

There's a considerable amount of battery power on board, actually,
since the peak current draw is well over 100 Amps at times. A few
milliwatts for a local jammer would therefore be a negligable drain on
resources. *However* as you've already guessed, jammers are banned, as
are EMP pulse type weapons and such like. The reason for this is very
sound, when you think about it: it makes for really bad TV. The
producers want to see as much *action* as possible. You ain't gonna
get that if everybody's disabled everybody else's robot!
--

"I believe history will be kind to me, since I intend
to write it." - Winston Churchill

"Paul Burridge" wrote in message
...
On 2 Aug 2003 16:24:24 GMT, Allodoxaphobia
wrote:

You might try a section from a steel tape measure.
(Just don't select one of the cheap, Made-In-China plastic/mylar
ones. HI!HI!)
Additionally, try to mount the antenna in a "well" on the robot.
Even a well of 5-10 mm will help out.

Not sure about the tape measure suggestion, but mounting in a well is
something I'd not considered and am most grateful for the idea of!
Thanks...

Does it have to be a whip antenna? Why not try a horizontal circular loop?
Since you are working line of sight to the robot, the signal loss from going
from vertical to horizontal shouldn't matter much unless your transmitter is
extremely low power. A loop could be mounted inside a wooden or fiberglas
body and be pretty safe from attack.

Is there anything in the rules forbidding your installing a jammer
transmitter to cause the other bot to lose its command channel? Probobly a
poor use of what little electrical capacity the onboard battery holds, but
it would be one way of causing the other bot to freeze in place and become
like a deer in the headlights.
thanks, John.
KC5DWD