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

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

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,