[arm-allstar] A question for node builders bf888s

iabarry Buel iabarryyy at gmail.com
Sun Feb 10 15:44:02 EST 2019


 From a system perspective, the little HT nodes have several potential 
problems:

If the antenna is either on the HT or nearby, you could be getting 
digital noise in to the radio. Use the clamp on ferrite on BOTH the 
audio and power cables. Bundle the cables, don't have a spider web.

There is usually no real Ground as the PS is isolated and the case is 
plastic.  If you can, connect the low side of the HT and the RPI 
together and then to a real earth ground.

Put the RPI in a case, then wrap it in alum foil to see if that makes a 
difference. You can't leave it that way as it will overheat, but it will 
help with diagnosing things.  You might also try shielding the BF888 for 
testing.
Does the BF888 LED blink when the RPI is NOT powered?
Or not connected to the FOB?

Look at the DC power source. SMPS can have RF crap going way up in 
frequency. Even the trusty 7805 regulators can oscillate if not properly 
bypassed. Swap the ps for something entirely different.

You need to look at a bigger picture than just the BF888.

Barry




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