Replies to This Discussion

Permalink Reply by hpux on March 4, 2008 at 8:25pm

Do you have an Amateur Radio license? With out one, I don't think you'll be able to achieve this goal with unlicensed spectrum.

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Permalink Reply by Michael Evans on March 4, 2008 at 9:20pm

no i dont ,do you have to have one to use some of the 900mhz modules?

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Permalink Reply by hpux on March 4, 2008 at 9:48pm

If the modem frequency is between 902 and 928mhz it is within the amateur band. All that means, in this case, is that amateurs are the "primary" on the band which means that they can interfere with you, but not the other way around. There are other restrictions to being unlicensed. If you find a modem that is "Spread Spectrum" you are permitted to transmit with 1 Watt of power. While that seems like a lot and many will claim you can get 20 miles or so of link it's unlikely. Attenuation from the atmosphere increases greatly with frequency, and at 400mhz I can get about 10 miles on a watt, but only just. I guess what I'm saying is: that is a challenge, the best you're going to find is a 1Watt SS modem, thats the legal limit. But, there is hope. An often overlooked system component is the antenna, and it is probably the most important piece. If you have line-of-sight to the plane and a high-gain antenna like a yagi pointed right at the plane you can probably pull it off.

As for specific modems, the paparazzi website has a nice list.

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Permalink Reply by Michael Evans on March 4, 2008 at 10:05pm

it doesnt have to have that much but its great to just get something good now so i dont have to worry later . i would only fly to 2-3 miles a couple times, everything else would be within that.

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Permalink Reply by hpux on March 4, 2008 at 10:16pm

Then you should have no problem. I've been looking at the paparazzi page again and the Maxstream 9XTend modems look good, if not a little on the spendy side.

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Permalink Reply by Michael Evans on March 4, 2008 at 11:13pm

i just saw the aerocomm ones, how do they compare? they are half the cost of the xtends!!

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Permalink Reply by hpux on March 5, 2008 at 9:30am

I don't have personal experience with either, I worry a bit about the comment that the aerocomm's can interfere with the GPS. I think that could probably be dealt with, though. As far a brand-name goes Maxstream is slightly better known.

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ModeratorPermalink Reply by James Ross on March 5, 2008 at 11:42am

A couple guys in the robotics club were playing with two AeroComm AC4490-200 transceivers and BASIC Stamps this past Sunday. They were getting close to having them talking, but haven't yet. They'll be working on them later this evening, I imagine. I'll let you know how it goes. If they do get them working, I'll probably use them instead of the XBee modems I was considering.

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Permalink Reply by Michael Evans on March 5, 2008 at 7:24pm

yes an abandoned, military base miles of nothing. i would like to explore around because ive seen some cool stuff on google earth but the pictures suck and the roads are blocked but the airspace is not restricted. my slowstick can only go 1.5 miles before i start to worry, but my scratch build shadow has flights of over 30 min and still room for more mah.

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ModeratorPermalink Reply by James Ross on March 5, 2008 at 11:19pm

If you stay low enough and away from airports, it wont really cause a safety issue. The military is really interested in developing automated collision avoidance. I imagine the eventual solution will be some kind of protocol that broadcasts location and predicted flight path of everything in the sky. Possibly combined with computer vision. Who knows.

As for the AeroComm transceivers...they weren't working on them tonight.

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Permalink Reply by hpux on March 6, 2008 at 7:13am

This already exists. It's kinda in it's infancy, but intended to replace the radar/transponder model used now. I'm sure they'll keep radars around, but it's much easier for other planes to just listen to a common radio frequency for updates to nearby traffic. I think it's called "TIS" for traffic information service. Computer vision would probably be a challenging and ultimately unrewarding way to do this. i think, because the government has a lot of control over what's in the sky. This makes it possible to implement sweeping changes such as TIS, or systems like it.

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Permalink Reply by hotelzululima on March 9, 2008 at 7:52am

Hi Michael,
(warning topic drift to michaels flight area)
old Ft ord property too interesting? just watch out for the approach paths to monterey airport, downwind is often over the town of seaside itself and the ft ord properties themselves and is low, the planes are on approach remember?

In addition life flight(s) to/from CHOMP in carmel are often low(under 400ft), couple that with occasional low fast passes of private helicopters off the seaside beach(only just over the water) at fremont exit ,to the terror of the paraglider pilots locally.


A safer bet would be to stay to the eastern half of the ft ord property and also have access to the large fenceless agricultural fields surrounding all around, makes retrieval real easy, no fences of course you may have to pay for any crop damage you may cause, and you want to make SURE no agricultural aircraft are NOT arround(watch out for the skydiving ops at Ft ord airstrip.). Another hazard to watch for on landing/takeoff are those high tension towers that DONT show on google earth.



The area Michael is chatting about is excellent EXCEPT if retrieval needs to take place , unexploded ordinance and regular burns scheduled for this year occupy some of this areas flying spots , other than the above caveats michael excellent choice. I have just been over flying the are myself with google earth to get an idea what it looks like.

gwen

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