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Old 17-07-2020, 15:03   #31
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Re: Suddenly Strong, Many GPS Signals

I think this GPS signal boost has been recently explained in a number of threads here. Look for ?GPS, US, jury, Commision, etc. There was something there about another company creating interference, etc.


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Old 20-07-2020, 07:22   #32
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Re: Suddenly Strong, Many GPS Signals

A follow up to my original post:

After further testing on my new computer and new C-Type USB hub, I can see that the USB configuration can have a dramatic effect on the reception of GNSS signals. On my new system configuration I have the GNSS antenna on one port of the C-Type USB hub. I also have a portable hard drive and a thumb drive on that same hub. Under normal operation the GNSS display will show around 14 GPS satellites in view and 12 in use for a fix. When I start additional activity on that hub (e.g., writing a large file to the thumb drive), the SNR values displayed drop dramatically and the GNSS antenna will drop 1 or 2 of the satellites from the in use list (GSA NMEA sentence). When the additional activity ceases the SNR values will slowly increase and within a minute or 2 the SNR values are all strong and the GSA sentence is reporting 12 satellites in use. A similar effect happens to the GLONASS satellites the antenna is tracking.
So the USB port configuration can have a significant effect on GNSS reception. I don't know if this is because the additional activity is causing noise or drawing too much power from the other hub ports. I used a similar USB hub configuration on my old computer so a failing USB port on that computer might explain the dramatic improvement I reported in my original post when I moved to a new computer.
If I move the GNSS antenna to a separate USB port on my computer the GPS reception is not affected by I/O activity on the hub.
This testing was on my personal computer, not the computer at my nav station, The navigation computer does not provide power to the GPS-only receiver for ship navigation, but I definitely would not use a USB hub for GNSS navigation. Although the effect on SNR values was dramatic, the GNSS antenna never lost it's fix and the HDOP value never went above 5 feet, so the real effect may not be that important.

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Old 20-07-2020, 08:14   #33
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Re: Suddenly Strong, Many GPS Signals

Running multiple devices with high power requirements off one USB port is not a good idea. USB C port has a maximum output of 15W (3A @ 5V) If there is not enough power available, it's not surprising that the GPS sensitivity goes down.
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Old 20-07-2020, 08:36   #34
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Re: Suddenly Strong, Many GPS Signals

I got the impression that the USB hub is powered from a power supply rather than the host USB port?
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