I have a sparkfun f9r pi hat that is working fine with an l1 antenna I used on another project. I’m able to see data with both the python interface and ucenter.
I switched to a new top106 antenna I got last week with a tnc to sma adapter cable and all of the satellites immediately drop to zero in ucenter. I’ve tried disabling a few types of beidou and glonas to see if maybe it was a baudrate idsue but I still don’t see anything.
Hi Jefswat,
This could be:
A faulty antenna
A faulty cable
Or the F9R Pi Hat isn’t delivering enough voltage to power the TOP106 active antenna
Are you confident enough to try the following?
Take anti-static precautions - you don’t want to zap the F9R RF_IN.
Use a digital multimeter to measure the DC voltage at the u.FL antenna connector center pin RF_IN - marked by the arrow in the attached photo. Measure between RF_IN and GND. Do this with the antenna connected.
Close to 3.0V indicates all is well.
Zero volts or close to zero volts indicates a cable short.
3.3V indicates a cable open circuit.
A voltage around 2.5V or below indicates the antenna is connected but is drawing slightly more current than expected, and the 33 Ohm current limit resistor on the Pi Hat is limiting the voltage.
If it’s the current limit resistor, you can try the following:
Take anti-static precautions - you don’t want to zap the F9R RF_IN.
Use a paperclip or a short length of wire to jumper (short) the 33 Ohm resistor R2 - highlighted in the photo.
Watch the signal strengths in u-center. Do they start popping up with the resistor shorted?
If the signal strengths return to normal, 33R is too high for the antenna you have. The solution would be to reduce the resistance by soldering e.g. a 10 Ohm resistor on top of (in parallel with) the 33 Ohm one.
Let us know if you need more help with this.
Best wishes,
Paul
Hi Paul,
I am reading about 3.3v with the TOP106 antenna attached and 2.7v with the working L1 only antenna attached.
However, I observed when switching to the functioning antenna that does not require a TNC to SMA adapter cable that i am completely missing the center Pin on the SMA end of the cable in the TNC to SMA adapter cable that i purchased with the antenna. Can i get a new one delivered or do i need to return the cable? Its listed as 6.95$ on the website.
Thanks,
Jeff
Hi Jeff,
Do you have this cable? https://www.sparkfun.com/products/14132
If so, it is a reverse-polarity cable - for RFID projects. The center pin is supposed to be missing - both ends…
You need one of these instead:
0.3m: https://www.sparkfun.com/products/21739
10m: https://www.sparkfun.com/products/21740
Best wishes,
Paul