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RF Noise From Ultimate GPS Breakout
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RF Noise From Ultimate GPS Breakout

by mrgougeo on Mon Aug 05, 2019 8:59 pm

I recently purchased the Ultimate GPS Breakout board, I found some noise being transmitted at 1Hz from the TX line of the GPS device.

Behavior:
    When powered with 5V or 3.3V a beep noise is heard on the radio every second
    The beeping noise correlates to UART data received on a raspberry pi
    Noise is present when receiving AM signals on aviation band frequencies (100-130MHz)
    SDR analysis showed noise on many isolated frequencies from 100-1000MHz corresponding with UART data transmission
    Noise is only heard when the receiving antenna is close to the TX line of the board, attempted with RX and other lines and it does not occur.


Has anyone had similar issues or may be able to suggest a method of eliminating this transmission of noise?

Thanks!

mrgougeo
 
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Re: RF Noise From Ultimate GPS Breakout

by franklin97355 on Tue Aug 06, 2019 3:16 am

If you power the GPS with a battery and have nothing else connected to it do you still get noise?

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Re: RF Noise From Ultimate GPS Breakout

by mrgougeo on Tue Aug 06, 2019 9:13 pm

Tested with just a LiPo battery connected directly to the GPS chip for power, no change in behaviour, still get 1Hz noise on some frequencies.

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Re: RF Noise From Ultimate GPS Breakout

by adafruit2 on Tue Aug 06, 2019 9:55 pm

you can shield the TX pin, put a resistor in series...its sending the 9600 baud data on that pin once a second, its normal

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Re: RF Noise From Ultimate GPS Breakout

by mrgougeo on Wed Aug 07, 2019 8:08 pm

Thanks for the advise!

How does one shield the TX pin? Am I expected to use a small coax cable?

Also does a "resistor in series" mean pull up/pull down? Or between the TX and RX pins?

None of the other GPS modules that I've tested have given off such strong RF noise from the TX pin.

mrgougeo
 
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Joined: Fri Mar 22, 2019 9:44 pm

Please be positive and constructive with your questions and comments.