John E Cache

http://www.gpsvisualizer.com/ is very good. It works online so any browser on any computer works.

Just curious. Were the "offsets" North/South East/West offsets. If so, couldn't you just add the offsets.

If that were true, these components wouldn't last very long! More to the point, if you see the problem begin, and put in a pair of cells that match the voltage that was present during the most recent calibration, the operation returns to NORMAL -- nothing is changing about the characteristics of the chip over the course of a few hours. What's changing is the externally applied voltage. Keep giving that chip the same voltage and it won't mess with you. The part that Garmin is using is apparently not one of those that uses an internal voltage reference for the A>D off what amounts to an internal Wheatstone bridge, and either the chip's analog portion is being asked to run off Vcc, or there's no decent regulation on the analog voltage reference. No good reference voltage, no good output. Further, the sensor elements are likely NOT made of a "doped semiconductor" material. The newer chips are usually made of Permalloy (a nickel-iron material) or some other magnetoresistive material (ala Honeywell, PNI, ALPS and Memsic, etc.). The old indium components are for older design Hall sensors (ala AKM). OK, I admit I was trying to poke you a little for fun. You haven't convinced me, though. The voltage argument leads to some pretty weak conclusions, in my opinion. I can not believe the GPS has no internal regulated voltage, for instance. The speed of CMOS varies with voltage. Speaking of CMOS, the p transistors in CMOS logic also degrade over time. I have always wondered why calibration? When I read an article about Hall Effect chips and how they need to be calibrated periodically, I started discounting the voltage theory. The voltage theory really started crumbling when my new Android phone started asking me to calibrate my compass periodically. Wheatstone bridge? Cmon, man. You can do better than that. :-)You keep bring up other sensor types, but never say if they need to be calibrated. Do you have an example product that uses these parts?

After you install those, you MUST recalibrate. The voltage is higher than what your device has seen from previous cells that you have installed. It's another stake in the heart of other theories about why Garmin's compasses drift. It IS voltage. I thought I would respond to your comment now that you have pointed out the battery voltage drops with use. That is the main reason why am leaning towards the idea that voltage is a Red Herring and has nothing to do with calibration. My alternate theory you mention is that the doped semiconductor used in the sensor changes when an electrical charge is passed through it. The amount of charge in one battery charge ages the semiconductor enough to warrant recalibration. Also, I have heard "goofy" and "erratic" used to describe normal magnetic compass behavior. In fact, I used those words before I figured out how the compass works.

The whole point of the magnetic sensor is so the GPS knows which way the GPS is pointed. The arrow is supposed to stick on the direction of the cache no matter which way you turn.

I did the same upgrade when my Merri Gold fell off of my kayak and now resides on the bottom of the Tualatin River. The 60csx is infinitely better except for one thing. On the Merri Gold if you wanted more waypoint storage you just got a bigger flash card. The 60csx has a limit to the number of caches/waypoints.

I am only guessing that if you "go to" a cache on a river that is added as a "road", the DeLorme will route a along the "river" and tell you the true distance. I assumed the OP was asking for routable when he referred to cgsmapper, which makes routable maps. It is only a guess because I only use the DeLorme mapping software.

I stopped by Ham Radio Outlet while out biking and they have the Wouxon for $119.(no sales tax)

You are in error that the pn 40/60 method would work better. What you describe is the same (just different termonology) with the Garmin. A track on the Garmin works just like your routeable trail. However, while not relavant on a float trip, when you are using it to take a hike, the Garmin track manager will also determine high and low points and add them to your route so you can see how far you have to go until the top. Garmin will also add elevation profile to the track. I think the terminology is different because they are different. DeLorme is firstly a map company. I have used DeLorme Street Atlas for years for trip planning. If you add a road it will use that road for routing a trip if the road is a short cut. "Routable" is not the same as adding routes( or tracks or whatever you want to call it).

I did a lot of kayaking on the Tualatin and the GPS was mainly useless for distance, like you said. I mostly used the map screen and kind of estimated distance. Planning the trip times was easy because the river had mileposts and distances between launch sites. I have manually made bike trail routes by dropping a lot of extra way points in mapsource to follow curves. I just checked and I don't think CGSmapper does routing any more. "Commercial routable version is no longer available."

Map: http://www.nzemperor.com/#mapt ABC news: http://abcnews.go.co...ory?id=14447934

I have a couple of ideas you can think about. A line of LEDs that displays a message when you move it. http://www.adafruit.com/products/20 Some kind of voice recognition SW. Like those elevators. I remember a long time ago someone here had a cache the would light up a beacon every night at midnight. People would gather at the coordinates and wait for the light.

Challenges maybe?

The electronic "compass" is a very puzzling topic for me. Why some people like it a lot and some people don't like it all is a mystery to me. If you buy a GPS with a magnetic sensor, try this demo. "Go to" or "find" a cache. Put the GPS on a flat surface. Hold a pencil or straw above the arrow and sight along it. The pencil should be pointing to the cache you are "going to". Hold the pencil steady and rotate the GPS. The arrow should swing to line up with the pencil. Some will say the arrow turned "erratically" or say that "walking speed" affects the arrow, but I just say it's a beautiful thing and would not be without a magnetic sensor.

I bought a Palm battery on ebay for under $10. Also, I use GPXSpinner to convert the GPX to a web page for my Palm. I convert the web page to an iSilo doc. If you too use GPXSpinner maybe just the web page can be loaded to a tablet or smart phone or iPod for viewing.

Mostly - as long as we agree that although you say "Garmin's problem is that their filters are not sharp enough", we can extrapolate from that to say "None of the GPS manufacturers' filtering is sharp enough, and neither should anyone have thought to attempt to design them to handle a problem like this. Nor is it clear that given the power levels involved, that it is even practical to do so." I used Garmin as an example because they were the one's who's response was posted here. I have since learned that they designed their filters with low power sat signals on adjacent bands in mind. I now see their point and think Garmin has a valid point. Your CB story is the similar. I should point out EEs argue with each other on occasion. :-) The CB band is 11 meters or 27mhz, I think. Ham amplifiers that work for the ham 10 meter band(28mhz) band work for 11 meters. One difference is you are talking several CB channels in one band, not adjacent bands. My guess is that your old CBs probably were not selective enough to select only the weak channel in the presence of an illegal high power channel. Hams can put filters on their neighbors TV if they are running high power and it gets into their TV. The problem is the ham is perfectly legal, like LightSquared, and a filter is not legally required by the transmitter owner. I can see several towers on the west hills of Portland. They do not interfere with each other by design and governed by laws founded by Fourier in the 1800s. Just because someone draws a nice picture of the radio spectrum with the bands in a nice order, you can not infer that nearby bands interfere with each other. The math is much more complicated than a simple picture.

Late. Maybe you have internet on your trip. I always stop and see the prairie dogs on my trips back to Minnesota. Town dogs

Mostly - as long as we agree that although you say "Garmin's problem is that their filters are not sharp enough", we can extrapolate from that to say "None of the GPS manufacturers' filtering is sharp enough, and neither should anyone have thought to attempt to design them to handle a problem like this. Nor is it clear that given the power levels involved, that it is even practical to do so." I used Garmin as an example because they were the one's who's response was posted here. I have since learned that they designed their filters with low power sat signals on adjacent bands in mind. I now see their point and think Garmin has a valid point.

No, he didn't miss your point. You are incorrect. The interference being discussed here is sideband interference, not harmonic interference. You seem oddly fixated on one and completely ignorant of the other. Once again, slowly. A high power in one band will always leak into adjacent bands if there is information being transmitted. It's pretty basic physics. I guess I don't get what basic physics you are talking about unless you can cite a reference. I learned about frequency domain and Fourier series and Laplace transforms in third or fourth year electrical engineering. The modulation method is designed so the bandwidth of the signal fits in the band. The bandwidth of the signal does not increase when run trough a linear amplifier to increase power. As far as the two sidebands from amplitude modulation(AM) the sidebands and carrier frequencies fit in the band. In the "band pass filter" link I cited, the slanted sides of the filter in the GPS may be in the adjacent bands and if the Lightspeed signal is towards the GPS end of their band the signal may be in the skirts of the GPS filter. That's all I am saying. If you are listening to radio and drive by a powerful station it appears to be bleeding over, but in fact the signal is stronger than the filter can filter out(even the flat floor on the sides of the filter diagram). As far as harmonics, I think the oscillator of the transmitter as a spinning wheel with a white dot. If you count how many times the white dot passes the frequency is the count divided by time. If you add a dot you get a harmonic at twice the frequency. As a side note for listeners: Fizzy and I like to argue. At least on my end it is all in fun if it does not get personal. "You seem oddly fixated" and "slowly" is getting close being personal, but not there, yet.

Forget harmonics - that's not the issue. You missed my point entirely. Only harmonics can be generated and they do not fall in the adjacent band. So there is no GPS interference. Like you, I was trying to tell someone to forget the bleeding into adjacent frequencies interference. I also pointed out that the band pass filter is swamped in my other post. I am glad another EMI guy agrees with me.

Reading that article should be enough to show you that bandpass filtering does not come for free. you should also know that it is physically impossible for Lightwave to keep all their power at their assigned frequency; some will inevitably leak to adjacent frequencies. Regardless of modifications to the GPS hardware presently in use, the Lightsquared towers will cause GPS interference. It's physics. In the frequency domain transmitter noise is generated on multiples of the frequency(harmonics) you don't bleed over into adjacent frequencies. The first harmonic is twice the frequency, for example. The FCC has very specific rules on the transmission on unwanted frequencies. I have had to sit over a spectrum analyzer in the radio quiet north woods tracking down noise sources in computer systems so they would pass FCC qualification. Your bold type doesn't sway me and like I said I would prefer a tech doc.

I guess this is the "official" thread. I was posting under topic Lightsquared jamming GPS signals and the thread was closed. Basically my minor nitpick is that Lightspeed is not jamming the GPS band and Garmin's problem is that their filters are not sharp enough(the sides of the filter curve are not vertical enough) to knock down adjacent powerful frequencies. I know the filters aren't strong enough for non-adjacent frequencies because my Garmin fails near TV or cell towers. Band-pass filter If anyone sees articles that are more technical, please post a link.

GPS is different because it's spread spectrum. There isn't a strong frequency peak you can just use a narrow filter for. The peak is spread out and barely above the noise, so you need a wide front end to get the signal at all. It's even worse for high accuracy commercial receivers and high sensitivity consumer receivers that need to go wider to get as much signal as possible. They can handle a reasonable amount of raised noise floor, but LightSquared's scheme is far from reasonable - even their "reduced impact" plan. Their spreading overlaps with GPS's spreading too much, and is a lot stronger. OK, I may be getting it ... or not. In my world the FCC assigns a range of frequencies called a band. You can use any frequency for a transmission as long as any type of modulation of that frequency does not generate frequencies outside the band. The modulation type can be AM, FM, SSB, spread spectrum and on and on. Are you saying the FCC is proposing overlapping bands or sharing of a band? EDIT: I may be missing a key point about spread spectrum. My thinking it is just multiple frequencies for one info stream.

"bleed over" makes no sense to me as an engineer and a ham operator. What do you mean?. Transmitters can make noise on multiples of the frequency called harmonics. Harmonics don't affect nearby frequencies(the first harmonic is double the frequency). A transmitter can be too strong for a receiver's front end tuner band pass filter, which affects all frequencies, not just nearby ones. That is solved by moving away or fixing the receiver. Many a ham has put better filters on their neighbors TVs, even though hams are not legally required to install filters. I think maybe the front ends of today's modern GPSs are much better than TVs IMHO and they should be fine. I have had GPS problems near high power cell or TV towers. I have pretty much ignored previous threads so this is my first reaction..

I did the hall effect experiment in college. You pass a current through a doped semiconductor and the current splits into holes and electrons, which causes a voltage at right angles to the current. The voltage is proportional to current and field strength. So you need a known current source that is not dependant on voltage. I still think the battery voltage may be a red herring.