Minima QRP Transceiver The Audio part.

AF Amp

After reading on the freelists i decide to test the audio amplifier, because there was lot of ides to change the design i have LM380 and LM386 in the box. The original amplifier could give around 600mV rms over 8 ohm before clipping. The LM386 could give 2,8V rms over 8 ohm P = U*U/R = 2,8*2,8/8 ~ 1W, LM380 give less power.

47 uF out. -3dB @ 200 Hz, 0 dB @ 100 kHz

5 mA no input signal.

135 mA @ 1 W out.

input 150 mVrms  @ 2,8Vrms  out.

Pre Amplifier

Max out 940 mV rms before clipping. Around 1 mV in. T16:c = 11V.

T15:c = 8,2V , T15:e = 6,4V, Around 2 mA current.

Mic Amplifier

30 mV in around 40 mV rms out.  -3dB @ 20 Hz  -3 dB @ 10 kHz. there is a little maxi-ma @ 200 Hz around + 5-6 dB. T13.e = 1.5V T13:c = 5.1 V must be 7 mA.

Side Tone

Wen tone on gives around 100mV @ max volym on speaker output, Tx monitoring.

Around 1 mV @ C28 modulator. T17:c = 6,7V T17:e = 0,27V.

Next it is time to do the BFO, stay tuned SM4HNG, I relay like this building the Minima