For what it's worth, one of the antenna design projects I offered in my antenna class last year was a "telemetry antenna for high power rockets". One team took up the challenge, and produced a quadrifilar helix that could be mounted on the skin of a 4" fiberglass airframe; the idea being that circular pol was a good idea, and that the interior of a high power rocket was precious/dangerous.
I think I might try antennas embedded in fins as a student project for next year. jds On Mon, Apr 18, 2016 at 10:39 AM, Bdale Garbee <[email protected]> wrote: > Web Customer <[email protected]> writes: > > Copying the list since I've had this question before and getting a > discussion going about different antenna ideas could be fun. If you > aren't already a list member, see the bottom of the altusmetrum.org page > for a link to our list server and sign yourself up! > > > Comment: I have two of your TeleGPS units. Last month I attended a > > local HAM swap, which is something our Rocket club attends yearly to > > create awareness for rocketry. While there I thought I would ask > > around for a suitable “base station” antenna for my TeleGPS, which I > > had on display. Someone suggested that I could get more range from > > the antenna on the TeleGPS, because it was/is essentially only half of > > an antenna and that I simply needed to add an equivalent length size > > of wire to the ground side of the TeleGPS. Does this sound correct? > > That's a gross over-simplification, and not the whole story. It is, > however, something you're likely to hear again in the ham community > where the "default" antenna for many is the 1/2-wave dipole. A 1/4 wave > whip, which is what we're providing by default on TeleGPS and our other > flight boards isn't "half an antenna", it's just an antenna built to > different design criteria. > > Many books have been written about antenna design. If you're interested > in the topic, a good place to start would be the ARRL Handbook and/or > one of the antenna books from the ARRL or RSGB. Note that "conventional > wisdom" in HF space doesn't always map well to UHF, so focusing on ideas > that others have already discovered work well at 70cm could help narrow > your focus. > > Antennas in rockets get complicated by a lot of things, including the > dielectric influence of airframe materials, proximity of other metal > like all-thread in ebays, etc. After trying a bunch of things, we think > the simple wire 1/4-wave whip is a pretty good choice. However, I've > done some "creative" things, like loading up the motor case as an > antenna, loading up two fins (see the 'Fintenna' heading at > http://gag.com/rockets/airframes/YikStik3/ > for more details on that), and I'm currently building a 12" airframe > that will have full dipoles on 70cm mounted just inside the skin as far > From the 6" motor case as I can get them. So many choices! ;-) > > > Integrated antenna aside, my original search was for a unidirectional > > antenna that I could connect to my computer sitting on my launch > > prep-table, with the antenna affixed to one of my canopy legs on an > > extension pole. I would then use my 3 element yagi with my TeleBT and > > my phone while watching and visually tracking from the launch line, > > and just leave my computer running back at my prep table, to hopefully > > capture the flight. What is the best antenna for this application? > > The "problem" is that you want an antenna with good performance at high > radiation angles (since the rocket will be "up" during much of the > flight as seen from the flight line). Many sophisticated ham radio > antennas are explicitly designed to direct most energy to/from the > horizon for longer distance comms and just don't work all that well for > rockets in flight. A simple 1/4 wave over a ground plane, a patch, or a > quadrifilar helix on 70cm (or variants like the "Texas Potato Masher" > are all pretty good choices. An even better idea, but it can be harder > to arrange, is to get someone to back a mile or so off from the flight > line where they'll have a "broad side" view of the rocket through the > entire flight... that's often the best way to get all the packets, since > otherwise a ground station on the flight line is looking up at a > sub-optimal antenna radiation angle for at least the boost and coast > phases of the flight. > > In any case, just experiment! The ground software shows received signal > strength for each received packet, so you can easily see what works > better and worse, and it's fun to try things! > > Above all, have fun! > > Bdale > > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum > > -- John D Sahr --- Seattle WA --- [email protected]
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