[Elecraft] K1 tx alignment: cannot hear sidetone or monitor tone

[JT Croteau]

This may help.

K1 Builder Alert #3: Inability to hear transmit signal when making the TX Offset
Adjustment
26 Feb. 2001

Impact: All K1's

Background:
When making the 'Transmit Offset Adjustment' (K1 Rev D manual, page 47) on some
K1s no TX signal tone is heard. (This adjustment has you match the K1 sidetone
frequency with the TX offset.) The reason this happens is because on some rigs
we have two mute circuits that work almost too well. Q10 is a shunt mute FET,
and Q11 is a series mute FET. Jumpering OFS (as noted on page 47)  prevents Q10
from muting, but it does not prevent Q11 from muting. Some J309s mute so well
there is not enough AF signal leakage from U3 to U4 to be heard in the speaker.
TX offset can still be set using an external receiver as a reference, but the
following procedure is suggested if you want to use just the K1.

Modification to TX Offset Adjustment instructions. (Please read the TX Offset
instructions on page 47 first.):

1. Set the RX BFO properly first (K1 Rev. D manual page 40), by adjusting C20
until maximum amplitude is found using an AC voltmeter on the AF output, or
using Spectrogram to peak the AF signal on noise.

2. Then turn off the sidetone completely (StL 0).

3. Set the power level for 2-3 watts.

4. Jumper OFS.

5. Try adjusting TX BFO trimmer C13 to see if you can hear the beat note. If you
still cannot hear the TX-generated tone, temporarily place a resistor of 47k to
100k across the Drain and Source leads of Q11 to allow more audio to leak into
the AF amp at U4. Now you should be able to hear the TX tone well.

6. You can then increase StL to 1-5 or so to match the sidetone and TX signal
levels. You may need to adjust the StL and Power level slightly so both are at
about the same audio level for hearing the beat note.

7. When the TX offset adjustment is complete, remove the OFS jumper and the 47k
to 100k resistor from Q11.

--
 JT Croteau - W6FO - Canton, GA | K1 #292
 ARS #2,147 | NoGA-QRP | SEDXC | ARRL