Do Sats Ever Go Down/Become Unavailable?

kbreeden · 10-18-2005, 05:17 PM

This may be a stupid question, but I'm having a problem with my GPS and want to eliminate satellite problems as a cause.

I'm using the BU-353 and it has worked flawlessly for the week I've had it in my car. Even in the trunk, it always immediately grabs at least eight satellites. Today, for the first time, it will not grab any satellites. I have confirmed that the receiver is being recognized by Iguidance. Nothing has changed in my system since it was last working. It is sunny and clear outside. I have removed the receiver from my trunk and placed it in the open - still nothing. Is it possible something is going on with the satellites?

Thanks in advance.

Kevin

xdjxklusivex · 10-18-2005, 05:20 PM

Quote: Originally Posted by kbreeden

This may be a stupid question, but I'm having a problem with my GPS and want to eliminate satellite problems as a cause.

I'm using the BU-353 and it has worked flawlessly for the week I've had it in my car. Even in the trunk, it always immediately grabs at least eight satellites. Today, for the first time, it will not grab any satellites. I have confirmed that the receiver is being recognized by Iguidance. Nothing has changed in my system since it was last working. It is sunny and clear outside. I have removed the receiver from my trunk and placed it in the open - still nothing. Is it possible something is going on with the satellites?

Thanks in advance.

Kevin

could be :-)

?

kbreeden · 10-18-2005, 05:43 PM

Searched. Haven't found much except one poster saying that solar flares sometimes cause a problem.

greenwire · 10-18-2005, 05:48 PM

Solar flares, atmospheric conditions, bad power to your reciever, other EM interference in around the same band...

All those things can contribute to you not seeing a satellite signal.

As far as a it being a problem with the network of satellites, that's not really plausible. One or two satellites might go down, but there's about 26 GPS satellites up there and i think 3 are backups anyways, so i doubt it's that.

Also, GPS is very good at spotting it's signal. I remember hearing somewhere that a GPS reciever can hear it's timecode and get a signal buried under 10db of noise, and that's pretty damn impressive.

Anyways, make sure your reciever has a clear view of the sky, is running off battery power and isn't recieving any interference from high frequency switching electronics (power supplies, motors, light dimmers, flourescent lights, laptop backlights, wifi cards, all kinds of stuff)

Good luck!

kbreeden · 10-18-2005, 06:24 PM

Big help. Thank you!

lez · 10-18-2005, 06:47 PM

gps signals are weak. good cloud can reduce signal 50-70%, but I dont think the sats transmit full power all the time.

In peacetime the US military may reduce power to save on power, IYSWIM.

I often on a clear day get 7 sats, on a cloudy day 3-4 etc. But I'm urban and dont have a clear sky view at the best of times.

0l33l · 10-18-2005, 06:55 PM

Bad battery

Enforcer · 10-18-2005, 07:16 PM

Quote: Originally Posted by 0l33l

Bad battery

send it to the naughty step

dhowse · 10-18-2005, 07:32 PM

GPS signals are L Band. They are not seriously attenuated by clouds. You've got to get up to Ku/Ka Band before you take big hits due to rain clouds.

GPS xmitter power is constant. There is no need to save power on these birds. Battery power is only needed for breif eclipse periods. The accurcy can be easily degraded by turning Selective Availibility back on (It's currently turned off).

Don't forget these are moving satellites in five different planes. The number of satellites tracked is primarily determined by visibility.

And yes, I am a Rocket Scientist,

kiztope · 10-18-2005, 07:52 PM

Quote: Originally Posted by Enforcer

send it to the naughty step

0l33l · 10-18-2005, 08:22 PM

Quote: Originally Posted by Enforcer

send it to the naughty step

lez · 10-19-2005, 03:20 AM

##

Oh hang on I got it, the naughty corner.

We dont have steps, seen them outside houses apartments etc on american shows and ppl just sit on them like drug dealers........

If you sat outside your house where I am you'd be visited by drug dealers trying to sell to you or to KTF out of you.

lez · 10-19-2005, 03:25 AM

Quote: Originally Posted by 0l33l

Bad battery

OK I have managed to get it open, it was well glued but a whack with a hammer got the case open.

I cant find a battery anywhere but I think I pulled a wire off the usb plug.

0l33l · 10-19-2005, 03:26 AM

Quote: Originally Posted by lez

OK I have managed to get it open, it was well glued but a whack with a hammer got the case open.

I cant find a battery anywhere but I think I pulled a wire off the usb plug.

Well, I thought that the BU-303 had a battery which died pretty soon. I guess the BU-353 is different.

lez · 10-19-2005, 03:34 AM

Quote: Originally Posted by dhowse

GPS signals are L Band. They are not seriously attenuated by clouds. You've got to get up to Ku/Ka Band before you take big hits due to rain clouds.

And yes, I am a Rocket Scientist,

And me a radio amature and ex electronics engineer, been working on cars since I left school and playing with computers for 25 years, there is no radio signal known to man that is _not_ affected by atmospheric conditions.

I dont care what band the signals are in, I work in Ghz/Mhz/Khz, but the PROOF is the readings, I get better readings on days with no cloud cover.

I'm static, the car has not been driven in nearly 2 years so its not different parked positions etc.

I will backstep a little here and agree the point the water vapour is unlikely, but its the readings, unless the cloud cover causes something in the higher atmosphere that is affecting it?

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