+StarDoc Posted February 12, 2007 Share Posted February 12, 2007 Yesterday while driving with my Legend Cx, I experienced several signal losses. The GPSr lost all the satellites simultaneously, then gave me the "Lost signal" message. The first time I was willing to wave it off as the local trees I was driving through, but it happened several more times during the morning, and again later in the evening. The later occurances happened in clear areas. It took several minutes each time to even see any satellites again, and another minute to lock again. The final time the signal never came back in the 30 minutes of driving I had left. Restarting the unit had no effect, nor did starting with a new location to get a new ephemeris. It would simply sit there and then randomly decide to lock on again. I'm just wondering if anyone else has experienced this (especially yesterday), or if I should be worried about the unit itself. I've been using GPS unit for several years, and I don't think I've ever had this problem before. Quote Link to comment
MtnHermit Posted February 12, 2007 Share Posted February 12, 2007 I'm just wondering if anyone else has experienced this (especially yesterday), or if I should be worried about the unit itself. I've been using GPS unit for several years, and I don't think I've ever had this problem before.WOW, DajaVue!!! I used my Venture Cx yesterday afternoon, roughly 3-4PM MST, where I normally get 8-10 satellites, I was only seeing 3 satellites and it NEVER locked. All I saw was acquiring satellite. It gets weirder, this morning I went to those same location, I was trying to measure my mining claim corners. Where before the best average error was always 10-12 feet after 200 readings, this morning my average error was consistently 5-6 feet. My error numbers were under 10 feet just walking around. Perhaps, the Feds, having been playing with their satellites. What do you think? Hermit Quote Link to comment
+Klemmer Posted February 12, 2007 Share Posted February 12, 2007 (edited) No GPS system outages yesterday. They would be listed under the ADVISORIES section, each with it's own Notice Advisory to Navstar Users (NANU). Solar Flare activity is very low at present. There was a small X-ray flux yesterday, but if that caused problems with your Cx, I'd be surprised. But it's possible. Those "x" suffix units with the SIRF III chipsets are very sensitive... maybe TOO sensitive? Hmmmm.... Might want to keep an eye on the unit. MIGHT have been some local interference, but also unlikely (or illegal if there was...). Edit: There WAS a Coronal Mass Ejection (CME) event yesterday. I'm still surprised it effcted your Cx, but certainly it is a possible explanation. "And today (editor - 10 Feb), a coronal mass ejection (CME) billowed over the sun's eastern limb. Are the two observations connected? We'll know more in a few days. The sun's rotation should carry the farside spot over the eastern limb on Feb 12th or 13th, giving us a better view of its size and explosive potential. Stay tuned." Check your unit a couple times on 12 / 13 / 14 Feb. I'm going to try to remember to try a couple different (older ones) I have then. Edited February 12, 2007 by Klemmer & TeddyBearMama Quote Link to comment
+StarDoc Posted February 12, 2007 Author Share Posted February 12, 2007 No GPS system outages yesterday. They would be listed under the ADVISORIES section, each with it's own Notice Advisory to Navstar Users (NANU). Solar Flare activity is very low at present. There was a small X-ray flux yesterday, but if that caused problems with your Cx, I'd be surprised. But it's possible. Those "x" suffix units with the SIRF III chipsets are very sensitive... maybe TOO sensitive? Hmmmm.... Might want to keep an eye on the unit. MIGHT have been some local interference, but also unlikely (or illegal if there was...). Edit: There WAS a Coronal Mass Ejection (CME) event yesterday. I'm still surprised it effcted your Cx, but certainly it is a possible explanation. "And today (editor - 10 Feb), a coronal mass ejection (CME) billowed over the sun's eastern limb. Are the two observations connected? We'll know more in a few days. The sun's rotation should carry the farside spot over the eastern limb on Feb 12th or 13th, giving us a better view of its size and explosive potential. Stay tuned." Check your unit a couple times on 12 / 13 / 14 Feb. I'm going to try to remember to try a couple different (older ones) I have then. I thought of solar activity, but yeah, there was none, and I seriously doubt there was enough radiation from that CME to affect it. I used it without any problems during the last couple of solar storms. Ironically, yesterday I was at a Boy Scout camp teaching some Cubs about astronomy and actually observing the Sun. Not a single sunspot... I mainly used it from 7-9am CST, and again from 8:30-10:30pm CST. I had it on once or twice during the day but never noticed a problem then. I didn't even think to look for outages on the web. I ruled out local interference since it happened along a 100 mile stretch at random. I thought it was weird how it just suddenly cut out. A little alarming, since I've only had the unit for a couple of months. I'll definitely keep an eye on it. Thanks. Quote Link to comment
+Klemmer Posted February 12, 2007 Share Posted February 12, 2007 Hah!!! With a name likle StarDoc, you were sure to know all about Solar events! Didn't pay attention to the name until just now. LOL!! I dunnnooo -- that CME on the 10th could have done have been the culprit.... Quote Link to comment
MtnHermit Posted February 12, 2007 Share Posted February 12, 2007 I dunnnooo -- that CME on the 10th could have done have been the culprit....Doesn't it take days for a CME to get to the earth? Besides, would it have been the right frequency or is a CME white noise? Just what frequency does GPS work at in any case? Thanks Hermit Quote Link to comment
+EraSeek Posted February 12, 2007 Share Posted February 12, 2007 I believe that the CMEs have to be pointed in our direction to have an effect. Here is a real time site to watch for monitoring these effects: http://www.sec.noaa.gov/rt_plots/kp_3d.html Quote Link to comment
+EraSeek Posted February 12, 2007 Share Posted February 12, 2007 (edited) What is a CME? : http://antwrp.gsfc.nasa.gov/apod/ap070206.html Edited February 12, 2007 by EraSeek Quote Link to comment
+EraSeek Posted February 12, 2007 Share Posted February 12, 2007 the latest MPEG solar movie (within 48hours) : http://sohowww.nascom.nasa.gov/data/LATEST...it_304small.mpg Quote Link to comment
+EraSeek Posted February 12, 2007 Share Posted February 12, 2007 "The GPS signal frequency of about 1575mhz was chosen expressly because it is a "window" in the weather as far as signal propagation is concerned. " Quote Link to comment
+EraSeek Posted February 12, 2007 Share Posted February 12, 2007 "The speed of the solar wind varies from less than 300 km/s (about half a million miles per hour) to over 800 km/s depending upon the conditions in the corona where the solar wind has its source. " Guess that would be 2 to 4 days. Frankly I think it (your problem) is a glitch (scientific term). The sirf chips can be a little wacky sometimes, also my old map76 used to do some weird thing like that and it had to do with changing battery types. Might try just poping the batteries out and putting them back in again. Who knows? Quote Link to comment
+Paulsan Posted February 12, 2007 Share Posted February 12, 2007 (edited) I didn't know the Legend Cx had a Sirf III chipset. I thought you had to move up to a 60x or 76x unit to get Sirf III. Edited February 12, 2007 by Paulsan Quote Link to comment
+EraSeek Posted February 13, 2007 Share Posted February 13, 2007 Opps. Didn't notice it was a legend. No they do not have the sirf chip. Quote Link to comment
+EraSeek Posted February 13, 2007 Share Posted February 13, 2007 Anyway let us know what happens. Could be a loose connection. Quote Link to comment
+StarDoc Posted February 18, 2007 Author Share Posted February 18, 2007 Problem Solved! Sorry it took so long, but my week was especially hectic, so I didn't get a chance to play with it again until yesterday. The problem: my cheap radio transmitter I bought to listen to the iPod in the car. Tune the thing to 85.5 MHz (first default freq), turn it on, and watching the satellite display drop to zero. It must be putting out some nasty harmonics that reach all the way up to the GPS frequency. Changing the frequency of the transmitter makes the problem go away. This explains why the GPSr worked fine until I got to the car. Last weekend was the first time I'd used both the GPS and transmitter in the car at the same time. I was even getting good signal inside the middle of the main dining hall at the camp I was at last Saturday. Just not in the car. I don't know if anyone else has had this problem, but the transmitter looks just like the Belkin Tunecast II unit. Sorry, I don't have any manufacturer name, since I no longer have the packaging. Funny thing is, I'm running a ham radio in the car, and even transmitting on 50 watts, there is no GPSr interference (I have a trunk-lip mount antenna, so I don't do that very often anyway). At least it's an easy fix, and I don't have to call Garmin. Quote Link to comment
+EraSeek Posted February 19, 2007 Share Posted February 19, 2007 Hey thanks so much for the follow up! Always great to know the cause of these things. Quote Link to comment
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