[Elecraft] First pass... sidetone output tests

[Tom Hammond NØSS]

Hi folks:

OK... haing recovered from a near heart attack when I lost sidetone 
temporarily, I have the following measurements to offer.

My first tests were on the SIDETONE since I didn't have to provide an audio 
signal external from the K2.

SIDETONE TEST RESULTS

   1. Used three (3) 12 Ohms resistors in parallel to give 4 Ohm
      load at the 2-pin SPKR plug on the RF board.

   2. Set ST L (050) to produce 0.4V p-p @ RP7-8.
      On my (Field Test) K2, this generally produces
      a very usable sidetone level in the speaker.

   3. Voltages read at:
                O'scope    RMS DMM      Comment
       RP7-8   0.40V p-p (88.5mV RMS)
       RP3-4   0.22V p-p (81.7mV RMS)
       RP3-6   0.20V p-p (71.5mV RMS)
       U10B-7  0.20V p-p (74.0mV RMS)
       U9-8    0.29V p-p (106.7mV RMS)   BYPASS of U9
       U9-6    0.30V p-p (107.0mV RMS)   AF OUT of U9
       Spkr    0.26V p-p (92.0mV RMS)    @ 4 Ohms load
                                   Note: I get 1.4V p-p (743 mV RMS)
                                         across the 4 Ohm SPKR output
                                         load when ST L = 255

Test conditions:

   K2 #0008
   U8-4 (KIO2) mod installed
   Sidetone sine wave mod installed
   KAF2 NOT installed (Control Board KAF2 connector pins
     jumpered 1-to-1 and 2-to-2).

Equipment used:
   Tektronix 2236 Scope 10X probe
   Fluke 187 True RMS multimeter

Now, to break out the sig gen and do some RF voltage checks.

More later. I'd be REALLY interested to see if others obtain similar results.

73,

Tom  N0SS