ELECRAFT 59
BFO Test
The BFO (beat-frequency oscillator) will be tested in the following
steps.
Switch to the 40-m band.
Connect the frequency counter to the BFO test point (TP2),
which is on the right side of the RF board near the crystal filter.
Using the menu, select C A L F C T R . The counter should show
a frequency between 4908 and 4918 kHz.
i
If you see a reading of 0 0 0 0 . 0 0 kHz or one that is
changing rapidly, you may not have the frequency counter probe
connected properly, or the BFO may not be working (see
Troubleshooting). If you see a stable frequency reading that is
nowhere near 4908-4918 kHz, you may have installed the wrong
crystals in the BFO (X3/X4).
When you’re in frequency counter mode, the B A N D + and
B A N D - switches can be used to check the range of the BFO. First,
tap
B A N D + and write down the frequency reading below (typically
about 4916-4917 kHz). Then tap
B A N D - and write down this
frequency reading (usually about 4909-4912 kHz). Finally, calculate
the BFO range (high - low) in kHz. Typical range is 4 to 6 kHz.
BFO High Freq. ___________ (must be >= 4916.3 kHz)
BFO Low Freq. ___________ (must be <= 4912.7 kHz)
Range (High - Low) ___________ (must be >= 3.6 kHz)
If your BFO range is less than 3.6 kHz, you may have the wrong
varactor diodes installed at D37 or D38, or the wrong crystals
installed at X3 or X4.
If the BFO frequencies are shifted too high or too low, it may be
due to one of the following:
If you didn't calibrate the K2's internal frequency counter using
an external counter, it may not be reading accurately. If
possible, borrow an accurate counter and re-do the 4 MHz
Oscillator Calibration.
The BFO range shift could be due to the inductance of L33
being too high or too low. However, since L33 is supplied pre-
wound and tested, this is unlikely.
The leads of R116 may have been heated excessively during
soldering, shorting out a portion of L33's turns.
One of L33's leads could be broken. Look closely at the leads
using a magnifying glass.
One or more of the capacitors or varactor diodes in the BFO
circuit could be of the wrong value.
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