[Space] Debriefing Notes

Christie Dudley longobord at gmail.com
Thu Feb 11 18:34:11 PST 2010


Well, pointing down is obviously fairly important.  I'm with you on concern
for the size of the ideal ground plane.  I don't see any reason not to at
least try the dipole.  Isn't that what we're all about?  Trying new things?

Christie
_______
"The road of excess leads to the palace of wisdom." -- W. Blake.

The outer bounds is only the beginning.
http://www.flickr.com/photos/genriel/sets/72157623376093724/


On Fri, Feb 12, 2010 at 2:58 AM, Mikolaj Habryn <dichro at rcpt.to> wrote:

> 19" radius makes for a fairly large slab, and just using stiff wires
> in the shape of a cross would make for some dangerously pointy bits
> falling out of the sky. The dipole sounds simpler and safer, although
> I'm also of the opinion that it would be worth using a stiff antenna
> attached to the side of the payload, since that way it would stay
> dipole shaped after landing, which might be useful for finding it if
> we land outside cellphone coverage.
>
> I'm imagining that our foamshell payload will wind up torpedo-shaped,
> meaning we could attach the antenna to the side. If it's offset
> somewhat from the body, it would presumably also reduce the arc
> through which the rest of the body would attenuate the signal. Can we
> attach an antenna at multiple points along its length with the
> appropriate materials? Or does it really want to only be attached at
> the base and to have clear air around it?
>
> m.
>
> On Thu, Feb 11, 2010 at 4:42 AM,  <grog at piratelabs.com> wrote:
> > Ed's right... but even in this previous situation, a dipole would
> probably have been a major improvement over the configuration that was used.
> >
> > On the other hand, a vertical dipole made out of coax would be cheap and
> less prone to damage from a landing.  it could hang from the payload section
> and stay (mostly - wind dependent) vertical with a fishing-line weight
> attached to it.
> >
> > Gregory Stramback
> > grog at pirate.org
> >
> >
> >
> >
> > On Feb 11, 2010, at 1:10 AM, Ed Moore wrote:
> >
> >> Radiation pattern - with a vertical dipole, half of the energy gets
> radiated up into space. with a ground plane and downward facing
> quarter-wave, the energy gets radiated from the horizon down (apart from a
> null along the axis of the antenna in both cases).
> >>
> >>       - Ed
> >>
> >>
> >> On 11 Feb 2010, at 09:05, Christie Dudley wrote:
> >>
> >>> I was talking to a friend tonight about this problem.  He suggested
> instead of depending on a ground plane, that we should instead use a dipole.
>  What are your thoughts on that?
> >>>
> >>> Christie
> >>> _______
> >>> "The road of excess leads to the palace of wisdom." -- W. Blake.
> >>>
> >>> The outer bounds is only the beginning.
> http://www.flickr.com/photos/genriel/sets/72157623376093724/
> >>>
> >>>
> >>> On Wed, Feb 10, 2010 at 11:35 PM, <nils at shkoo.com> wrote:
> >>> Cool. Googling "ground plane antenna" shows some promising hits; they
> mostly look like they put 4 horizontal wires in a plus-shaped configuration.
>  (Greg, I think this is what you suggested a couple weeks ago).
> >>>
> >>> I found an antenna simulation program here that one can use to simulate
> the radiation pattern of a given antenna:
> >>>
> >>> http://home.ict.nl/~arivoors/
> >>>
> >>> It's not working very reliably under my wine installation; perhaps
> someone else can have better luck.
> >>>
> >>> -nils
> >>>
> >>>
> >>> On Wed, 10 Feb 2010, Greg Stramback wrote:
> >>>
> >>> Well, you're using VHF on the 2m ham band. The groundplane should be a
> >>> minimum of 19" radius from the center feed point / radial.
> >>>
> >>> On Wednesday, February 10, 2010, Jonathan Moore <moore at eds.org> wrote:
> >>> On Wed, Feb 10, 2010 at 8:30 PM, Christie Dudley <longobord at gmail.com>
> wrote:
> >>> How big of a ground plane do you need?  We had a bit of a metal plate,
> but
> >>> it was pretty small, relatively speaking.
> >>>
> >>> It depends on how the antaina was designed.um
> >>>
> >>> -Jonathan
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