Satelite Watching

It's always raining here. I see puddles.. :(

D from BC Amateur smps designer British Columbia, Canada Posted to sci.electronics.design

I'm sorry about that. It's kinda cold tonight 56*F might get into the low 40s. Oh, I see your around 30*F. I'm sorry about that. Mike :-)

This must have been a rare occurance, look how close the were. Maximum altitude is at ISS 17:44:57 STS 17:45:19 Within 22 seconds Altitude ISS 37° STS 38° Within 1° Azimuth ISS 44° STS 44° Same Distance ISS 549 km STS 545 km Within 4 km.

ISS = International Space Station STS= The Space shuttle- STS 129 Mike

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Try this. It shows other birds that will be in your view. Remember brightness is an inverse scale. Something negative is very bright.

Yes, That's what I used to find the ISS would be coming over. Then when we saw two objects, I tried to get back on that sight and it was to busy for the next few hours. Mike

y

er.

It helps to have an "atomic clock" when you do this kind of stuff.

My cellphone was close enough, but a compass would have helped pinpoint the rising direction better. 4 hours later and I'm still excited! Mike

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=A0 =A0 =A0 =A0 =A0 =A0 =A0 Mike

The phosphorus version is good enough. I "juice it" with a flashlight since I'm not working SWAT or special ops. ;-) You can pay extra for tritium, but it wears out. You shouldn't buy one used for that reason. The phosphorus version is under $40 and it will last a lifetime, or until it is lost or stolen.

I have a GPS with a compass in it, but you have to remember to calibrate them. Really annoying.

Next up of course is that damn magnetic correction.

Yech. I do some TV antenna alignments and the usual point to point wireless. I don't bother with a compass because they're not accurate enough. What works best is a road map, a plywood board, and some nails. Mark your position on the map with a nail, push pin, or pin. Mark the position of a distant mountain, building, or landmark on the map. Eyeball the line between the two nails to the distant mountain, building or landmark. All maps have true north marked on them. The direction of the map arrow is true north. I can usually locate true north to within +/- 2 degrees depending on the size of the map and the distance to the marker. Using multiple distant points improves the accuracy.

If you're into astronomy, sighting the north star also works well. Also, using a computer sky chart/map to locate easy to find stars.

One I establish true north, I like to mark it on the road, sidewalk, or deck with a line or arrow. I have a brass marker arrow nailed to my deck.

Calibrate? You have to be moving in order for it to work. Then, it will only tell you the direction that you're moving. If you only go a short distance, it's not going to be very accurate.

I don't do no stinkin magnetic correction cause I don't use no stinkin magnetic or fluxgate compass.

Incidentally, I have a really handy item for watching expensive birds. I made a panorama (stitched) photo of the view from my rooftop at home, at the office, and at my favorite astronomy meeting places. I then marked the azimuths every 10 degrees on the JPG. Although difficult to see the remote hilltops at night, I now have the azimuth of anything in the sky or between me and the surrounding hills.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

The "virtual" compass requires you to move since it bases direction on differential GPS readings. OK in a car, semi-OK on foot, worthless if the going is slow since the delta of distance is not significant enough to get a good calculation.

The newer GPSs have sensors in them. To null out the nearby magnetic field, you need to slow spin it around. Two revolutions generally. Or you can spin your body around and look like an idiot. The trouble is the GPS has to be level unless you have a 3-D compass. [Garmin doesn't, Magellan does. Too many complaints about Magellan gear, so you just put up with Garmin.] The GPS has a threshold where it will shift from magnetic sensor to virtual compass. You can really screw yourself up if you don't know about this.

Your technique is fine if you spot from the same location. If you are on the move, you realy do need a compass. Occasionally I'll see something off in the distance.[OK, OK, in denied access area.] Log your position, take a vector, then study it on google earth or a map. Other times I am DFing radio signals. Again, the compass does the log. Log everything in magnetic, then use your mag in magnetic, and you won't go crazy. Attempt to correct your readings and you are either correct or you just added twice the adjustment factor to your reading. Really not a good idea.

Aviation long ago decided on doing everything magnetic, probably to get around the confusion. Of course, they still use AGL (above ground level) and MSL (mean sea level) for altitude. You may recall either a Thunderbird or Blue Angel getting into trouble with this.

I use your spotting technique at times too. It depends on if I can do the preparation. Your scheme works better in mountain areas, which is where I use it since I know the various peaks and where the campsite is located.

Actually, it's not too horrible for determining the general direction of travel. However, totally useless for determining the azimuth of something from a fixed location.

I spent some time trying to get sane readings from the fluxgate "magnetic" compass in a borrowed Garmin GPS. The rotation method worked quite well, until I moved. When standing next to a vehicle, it was nearly useless.

Ummm.... orbital satellite spotting from a moving vehicle is rather uncommon and dangerous.

Sigh. I suppose the alien technology that they're hiding is better than a compass.

Ok. I'll admit to having added my declination instead subtracted more than once. Still, some additional practice and a few sanity checks against known locations should help.

Mostly true. All US runways are magnetic. So is the VOR. However, all sectional maps are based on true north. GPS navigation devices can be either way. Magnetic is a big help when using a magnetic compass for finding the runway.

Canadian aviation is really strange. The northern half uses true north, while the southern half uses magnetic.

Dunno. However, I've screwed up a few HAAT calculations on FCC license applications when I was doing them with just a calculator:

It works with any decent road map. You don't even need to sight the distant mountain peaks. Just align the map with the local roadways and it's already better than a magnetic compass. The most difficult part is finding a large flat area on which to place the map. When desperate, I use corrugated box cardboard and pins for markers.

Incidentally, I have a crude system of doing TDOA (time difference of arrival) hyperbolic RDF location on a paper map using two nails and some string. I'm slowly scribbling a web page on the subject, so no details until I'm done.

Oh, if you want high tech location and mapping assistance, there's GPS augmented reality.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

I wish I could turn the damn sensor off at times.

I was speaking in the general sense of navigation.

Anyone that tracks my posts knows I sniff around Groom Lake. Knowing the terrain makes it easy to know where to point the binocs or telescope.

I've concluded I'm certifiable! ;-)

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Those old schemes where you quickly switch between antennas work well for voice signals. I've found data channels don't do so well. I was told that it has to do with how the data channels are nearly always at full modulation. One of these days I'm going to hack two radios so they share one local oscillator and see if I can DF based on phase comparison of the last IF output.

The difference in distance between you and ISS and between you and STS was 4 km. This does not mean they are 4km apart. That would only be true if they were on a straight line from you to those objects.

The mission before this one, we went out to watch the ISS and saw the shuttle leading the ISS. Quite a treat and surprise. Although I had my camera, the lens was too long to get both in. Yes, you can sort of make out the ISS structure with a 500mm lens.

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Mark

A "Homer" works fine for continuous uni-directional data. It doesn't work well for half duplex such as Wi-Fi. They're really awful for situations where you hear multiple xmitters with the added bonus of collisions (i.e. packet data). There are workarounds, but all require decoding the data first and using a computah to keep track of which xmitter you're hearing.

It will work with one big catch. You'll have to replace the IF crystal filters with one that has a fairly stable group delay across the IF bandwidth. If you're working with data that has modulation components all the way to the edge of the IF filter, you're going to go through huge variations in phase shift between the carrier and the filter skirts. Building two matched receivers just adds to the complexity. OAR (Ocean Applied Research, now part of Cubic) once made an Adcock antenna DF system that had 3 receivers for measuring the phase and displaying the direction on a scope.

Personally, I think you would do better with multiple remote receivers and measuring the TDOA (time difference of arrival) at each receiver. Each burst of RF is time coded and packaged along with signal strength, GPS phase, and decoded data, and sent off to a central computah for processing. The time codes are critical as that allows storage, replay, and post processing. Spewing RF around Area 51 is probably a bad idea, so post processing make sense. Collect the time coded data on thumb drives, stuff the data into a computah on your way out, compute, and replay the captured data later.

Drivel: If you're thinking of doing it with a Doppler ADF, then please read my previous rants before blundering onward:

Those are 15 year old postings about a 35 year old product, but it's still generally accurate.

Did you ever build and try the 1090 Mhz AMOS/Franklin antenna?

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

[snip]

An example of British humor: I saw an old (1950s era?) British military training film clip on how to use a compass. The instructor stated that it was necessary to remove metal objects that could distort the readings from the vicinity. He proceeded to remove pocket knives, coins, pens and his belt buckle prior to reading his compass. He was standing next to a locomotive.

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Paul Hovnanian  paul@hovnanian.com
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Have gnu, will travel.

An iron belt buckle and brass locomotive?

I fiddled with the AMOS 1090 and didn't like the big dip in the vertical axis. No amount of running the optimizer could get rid of it. I do appreciate the NEC file as it helped me understand the program.

After studying all the AMOS designs, the best plan would be to use the

3 element inverted AMOS. It is a natural 200 ohm antenna, so I assume you could skip the combiner and the associated loss. That is, just slap 4 in parallel to make 50 ohms. I'll probably be bugging you off- line on this, but I want to hack more myself er since it builds character. .-) [Of course it also wastes time, but I consider the wasted time education.] The 3 element AMOS creates a near perfect "blob" in the vertical. I could see the quad 3-element inverted AMOS working for satellite use.

Regarding TDOA, I bought two Trimble (Datum) StarLoc disciplined 10Mhz time references at Livermore. New old stock at $30 a pop. What I fool that I didn't wipe the vendor out since he had three. But at the time I didn't know if I could make it work. Anyway, I think TDOA using time stamp and synchronization via GPS disciplined clocks would make TDOA work well, even if after the fact. If I had three, I'd be TDOAing. As it stands, I was nice enough to sell one at cost to a friend, so now I need two more. I wasn't thinking TDOA at the time.

If you look at Plane Plotter, they have a MLAT for 1090. [Not every plane reports position.] The big drawback is the MLAT position reference is some other plane in the sky that is position reporting. Some airports have a constant mode-s, so I suspect there may be a FAA MLAT in the works. However, if they built the 1090 receivers with capability to use GPS timing, it would work with a simple TDOA.

r.

If you google John Locker, he has satellite photos via telescope.