Test of PH508 audio levels.
Altec Lansing ABM-100 Stereo Computer Microphone.
Heathkit IO-4540 Scope.
1X Probe.
Breadboard bias circuit for microphone. Using 2 AA batteries and 2.2K resistors.
Old 02H35 Hi Tone: .275V PP
Low Tone: .200V PP
New 09A03 Hi Tone: .125V PP
Low Tone: .100V PP
New 10F25 Hi Tone: .075V PP
Low Tone: .100V PP
Side note:
The XTB-IIRs signal was seen during triggering.
On the scope trace. Must have been radiating from the PH508s power transformer.