OdBm is 0.775v from function generator. If you only have a meter to measure this with them make the freq quite low. Maybe 200Hz because not all meters have a great freq resp when measuring a.c.So!
I've got what's shaping up to be a pretty nice build going. I made gerber files of the PCBs which I will happily share once I get my unit tested and verified. In the meantime, I wonder if anyone can help me try to figure out a good calibration procedure?
I'll re-attach Spencer's most recent schematic (which I'm working from), along with some notes:
- VR1, the original documentation says: "Do not adjust, factory set"
- VR2, original docs say: "Adjust so meter reads zero when output has reached threshold of limiting." Seems easy enough, though determining when that threshold has been reached will require a method of some sort
- VR3 again says: "Do not adjust, factory set"
- VR4 in the original is a supply voltage trim, and is made obsolete by a good regulated 18V supply; not included on my unit
- VR5, docs say: "Adjust to give 0dbm at pin L with 0dbm being applied to
pin H." This might be a stupid question, but... dB milliwatts? How would I measure this?
- VR6 is another "do not adjust, factory set
VR1, I'm rather clueless what to do.
VR2, I'm pretty sure I can handle.
For VR3, the old hand drawn schematic appears to say "VR ADJ BIAS (at slo release)" and then another notation in proximity that says "4.4-5.4 V". I assume I adjust adjust this until I read something like 5v... somewhere? This VR eventually connects (through attack and release controls, etc) to the gate of Q10, so maybe gate-source voltage there?
VR5 my only question is... what test equipment do I need to read "dBm," (dB milliwatts, or could they mean dB VU?) and when they say "0dbM applied to pin H" do they mean... signal from a function generator? I'm just a bit confused.
VR6, on the hand drawn and annotated schematic, there's a note in red that says "Waveshape adj. (symmetry)(2f in) (at slo attack)" Off to the side, in black, there's a note that says "5.9k total" with an arrow pointing to the red annotation.
I lack the knowledge to truly understand every aspect of what's going on here in the design, so I'd appreciate if anyone could help me make heads-or-tails of this.