On Tuesday, September 9, 2014 10:41:29 AM UTC-5, Vince Mulhollon wrote:
I'm tempted to hook it up with RF gear in place of the regulator and sweep the board
Done. Results follow. TLDR is results not really what I expected.
Prop Console IO V2. All on board components installed, no ICs, no regs.
Connected test equipment to ground and where the 5V regulator output.
One meter length 50 ohm test lead BNC to alligator clips.
I'm well aware that poorly terminating a 50 ohm cable 1 meter long is measuring the cable more than the circuit above 50 megs or so, but its still at least kinda interesting.
RF gear designed for nominal 50 ohm impedance so its not happy but gives some results anyway.
Reactance increases with freq... do we have a resonance below 2 MHz so its going back up again?
2 MHz 0 ohms resistive 7 ohms reactive
4 MHz 1 ohm resistive 14 ohms reactive
6 MHz 1 ohm resistive 23 ohms reactive
That's as exciting as it gets at the low end. Nice and linear. No resonances or funny business below 20 MHz
Resistive goes up as freq goes up... skin effect? I'm sure there's measurement errors using 50 ohm gear to read single digit resistances, or there may be other measurement issues. Still I think it not entirely unreasonable I'm seeing skin effect resistance increases? At least its going up with freq LOL.
8 MHz 1 ohm resistive
12 MHz 3 ohms resistive
16 MHz 10 ohms resistive
As for resonances (noting I'm using a 1 meter 50 ohm cable):
23 MHz reactance infinity
62.2 MHz reactance zero
107 MHz reactance peak at 121 ohms
154 MHz reactance zero.
The data isn't really what I was expecting. I'll have to digest it some. Soon I'll be sticking ICs in this and bringing it up as a console IO.
With more motivation and time than I have, the logical next steps would be blasting 5 volt square waves down the power bus and probing various locations with a scope to see how they looks. I'm probably going to stuff the board with ICs instead and bring it up this weekend... Probably..