Hi,
my question originates from recent one in this list, but I'd like to put it in into
a new thread, to avoid confusions.
Intending to do a two-tone test of my K2, I decided to try a 1000 Hz single tone
first. On the ocsilloscope on antenna jack I expected a signal much like when holding
key down in CW.
Instead, I get something like an AM signal. It's modulated with the frequency of the
single tone test signal.
AntJack_1_watt_1_tone_1000Hz.jpgTo see if it is really the test tone frequency or may be +-50 or 100 Hz, I checked
RF board D9 cathode (out detector) and registered 1kHz sine overlayed on DC level.
RF_D9_catode_1_watt_1_tone_1000Hz.jpgI varied the test tone and cross-checked oscilloscope's time base, it really seems to
be the test tone frequency.
Emitter of Q8 on control board (ALC) has a constant level.
In CW - nice constant amplitude and usual K2's outstanding shaping.
I hope somebody can help me explaining the first oscillogram - where is this AM
coming from?
I did balance the carrier on KSB2 successfully. With mic jack disconnected, RF
amplitude is less than 100mV (checked both with the same scope probe and K2's RF
probe). Filters were aligned with noise generator and Spectran, lower roll-off freq of FL1
is about 400 Hz.
Test conditions: PC as tone generator, K2 power set to 1 watt, CAL probe removed, 40m
band, both LSB and USB tried, ALC shows one LED, dummy load on antenna jack, K2
powered from a 12V 7Ah battery. KPA100 removed; KSB2, KNB2 and K160RX are in.
73! Oleg
Locked
Mar 10, 2010; 12:00am
