Hello everybody.
?
My name is Jirka, callsign OK1IEC, and I am new in the group. Recently I bought BITX40v3 and built it in the Al box. RX is ok, comparable? with my K2 in normal conditions. The problem is with transmitting ¨C I am not able to reach more than about 1W of output power shouting very loudly into electret mike. Mike change does not help, pot R136 is in the full gain position.
I? decided to do some measurements: I? used Audacity software to produce 1 kHz audio and connected it to Mic pins of BITX40 via 47uF capacitor.? I need 280mV p-p AF signal to get 6W RF output power on my dummy load.
AF signal levels:?? Mic (C121): 280 mV p-p;? C122: 410 mV p-p
RF signal levels: C132: 1.3V p-p;? C134: 3.45V p-p;? C141: 3.25V p-p; C152: 8.6V p-p; C155: 51V p-p; Antenna: 50V p-p.
It seems the RF chain is ok but? AF stage Q12 has suspectly low gain. Components seem to be ok, Q12 Uc=10V, Ue=2.26V
Any idea or advice appreciated. ?
73! Jirka
?
Trafo T4 in BFO mixer ??? BTW I see the difference between schematic (D15, D16, R106) and real components on the pc board.
