wrote in message
...
I'm helping the SDSU mechanical engineering students with their Rocket.
See: http://www-rohan.sdsu.edu/%7esharring/sdsurocket.html

I've asked for help on this group before, but the response went over my
head.
I a reasonably skilled EE, with ZERO antenna design experience.
I would like to design an antenna that was conformal with the rocket main
tube.
The rocket is about 8" in diameter and all metal.
I need two antennas....
I have two channels a 70cm ATV transmitter and a 900Mhz non-ham telemetry
radio.

For the last attempt:

Telemetry: I put two 1/4 wave verticals on opposite sides of the rocket
fed them with a minicircuits splitter.
This worked well as I got data from lift off to impact.

ATV Last attempt I just had a single 1/4 wave dipole sticking out one side
of the rocket.
As the rocket rolled the signal faded in and out.

The last time I asked this question I got a response that I could not use
because I did not understand it.

So I'm looking for someone to help that can do the detail design.

IE provide instructions build a tobe with this pattern on it, hook up coax
here and trim this spot to adjust SWR.
I'm perfectly willing to get the fabrication done, but the design is
beyond me.

I realize that I'm asking a lot, but any one that wants to help with the
antenna can have a
front row seat in the block house to watch it launch, and some cool video
tape ;-)
(The launch will be at the MTA near Mojave, CA)

Paul (Kl7JG)


No takers, but it's only been a day... Antenna on a metal tube... sounds
difficult. Body roll confounds the problem. Sounds like your experiments
worked. What were the probs? Antenna drag and resulting instabilities?
I can only suggest searching on "patch antenna". Then there is a slot
antenna, but fabricating this as part of the body without weakening the tube
sounds equally difficult...and the dimensions may be all wrong to fit the
antenna correctly.

If I shift into speculation mode, I'd think about an end-fed antenna which
trails, but your "metal" rocket sounds as though the exhaust will be rather
hostile compared to an Estes engine.

Reminds me of an idea I have always wanted to try on the small model
rockets. Namely:
A on-board transponder for distance measurement. A 10 Meter one transistor
FM receiver feeding a simple 2 meter 1-2 transistor FM, xtal controlled
transmitter.
High power (100w if needed) 10 M mobile transmits a tone to rocket.
Therefore airborne RX and 10M antenna need not be anything great. Rocket
transponds tone on 2M FM. 2M antenna do-able on small rocket. Mobile
receives tone. Black box (easy hardware) in mobile simply counts a
reference freq from time of transmitted tone rising edge to received edge.
Suitable accounting of internal delays and choice of reference frequency
gives simple, direct readout in feet or whatever units desired. Calibrating
the display horizontally on the ground is possible.

73, And good luck, Steve, K9DCI