[amsat-bb] Re: 2.4GHz broadband router on satellite?
jarvideo at gmail.com
Fri Feb 22 13:02:48 PST 2013
Hello James, I just wanted to throw my two cents in on the protocols. I'm
not sure about the need for AX.25 implementation. The 802.11(Wi-Fi)
standard should server the purpose needed. AX.25 is a considerably limited
protocol. Low speeds, limited error correction, and frankly, it defeats the
purpose of putting a wifi router in orbit to begin with. One key feature of
802.11 is its ability to operate in less than ideal conditions. The
protocol natively supports error correction, multiple simultaneous users,
and can avoid data collision with "carrier-sense" technology.
Also, long distance shouldn't be too large a concern. I seem to remember
reading about a successful experiment involving high altitude balloons.
I may too not be entirely accurate on the above, I'm still in college for a
networking degree. I'm just going on what I've learned so far.
On Fri, Feb 22, 2013 at 3:06 PM, James French <w8iss1 at gmail.com> wrote:
> Lee and those who have responded so far,
> Those are the questions that would need to be answered before even
> considering this 'novel' idea.
> I use the WRT54GL as a reference since that is what I am familiar with.
> The WRT54GL would need to be almost redesigned because of space
> radiation conditions plus it may just not have enough output power to
> even be considered especially with trying to fit it into a microsat or
> smaller frame and then finding a suitable launch. Could the satellite
> utilize a modified 'backfire' antenna (referencing AO-40 2.4GHz
> antennas) that utilizes dipoles offset from the surface on every side
> and then use the surface of the satellite itself for gain?
> As for HSMM-Mesh, this maybe the software to consider for something like
> this as its robust enough for what I have played with three WRT54G
> around my area (EN82jg), both mobile and stationary. My laptop (a
> Fujitsu Lifebook T4020) is sensitive enough to pick up one 54g half a
> mile away using just the supplied antennas and if I add a BBQ style dish
> (from my AO-40 reception days) to replace the supplied antenna, I can
> almost quadruple that range. Granted the laptop and 54g are both at
> ground level and have a lot of obstructions. Still have to take it out
> to one of the local parks to see what I can actually get for range with
> no buildings. With the laptop being so sensitive, I can connect to the
> local McD's free wi-fi almost half a mile away better than I can my
> d-link router in the basement.
> As for frequency usage, going by the 'slide-band' chart (available at
> http://www.hsmm-mesh.org), there are 6 available 'channels' that fall in
> the satellite sub-band the way I am interpreting FCC rules. If the
> 'slide-band ' crystal modification is done, that gives 4 'channels' for
> use. Something to consider there about 'channel' hopping in the
> Greg, KO6TH, brings up about the timing protocols. Maybe the HSMM group
> or TAPR would consider looking at the protocols and maybe modify them
> much like AX.25 was done for packet back in the 1980's.
> Mark and Drew bring up about noise levels being unacceptable on a few of
> the lower bands. This might be mitigated with the use of the
> 'slide-band' modification by changing out the 20MHz crystal for a more
> appropriate frequency. As I noted earlier, more about the 'slide-band'
> mod for the 54GL is at the hsmm-mesh pages.
> So if some of these obstacles can be 'overcome', would this be a
> 'viable' consideration? Could something like this be utilized to gain
> the faster input speeds that are wanted for uploading/ downloading
> images, files, and maybe store and forward systems that could tie into
> the regional packet networks utilizing JNOS 2.0, WinLink, and FBB.
> I just miss having something that is more than just APRS-related on the
> satellites. This in no way is a knock on the present 1k2 sats, its just
> that my KPC-9612 has been VERY under-utilized since the mid-1990's and I
> miss having that fun :(
> I am not a rocket scientist, electrical engineer, or a sat designer.
> These are just personal thoughts to see if this 'idea' is even feasible.
> My thoughts could be seriously flawed and skewed and totally 'out of
> this world' to say. For all I know, this might be one of those bright
> ideas that would work better with a placement on the lunar surface as
> long as it doesn't interfere with EME work and can survive the harsh
> environment there. That would be a TOTALLY separate discussion in itself
> James W8ISS
> On Tue, 2013-02-19 at 10:12 -0500, James French wrote:
> > What are the possibilities of building a satellite that uses a Linksys
> > WRT54GL router with a modified DD-wrt or HSMM-Mesh software as a store
> > and forward BBS, to route a received request from one station to another
> > station, or even to connect to a on board networked camera to receive
> > images?
> > What kind of uplink power would be needed from the home station?
> > How fast could the speed(s) get theoretically?
> > How big would the antenna have to be on the craft and for the ground
> > station to even be able to do this adequately?
> > Would the doppler be too much to even consider this?
> > Would the space environment be too harsh for something like this?
> > This is just something I was thinking about this morning and thought I
> > would toss it out.
> > James W8ISS
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