I dreamed up a work around for Allards CW mod with mine!
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Add a 1K across C107. Feed Allards CW DC voltage to the common of D15/16
through a 10K!
Current flows through the diode and the new resistor to ground to
unbalance the mixer.
Bobs your uncle! My elmer used to say!
At 19/10/2017, you wrote:
Note that this fix is not
compatible with Allard's instructions for using the rig on CW.
Also, note that there are two PTT bursts.
Raj's fix is for the carrier burst that transmits out over the air.
There's also a kerchunk you hear in the headphones.
On Thu, Oct 19, 2017 at 01:31 am, Raj vu2zap wrote:
- The carrier burst on PTT is due to the C122 charging up through D15
or 16 unbalancing it and allowing a leak.
- Quick fix is put a 0.68uF cap from the common of D15/16 to the atten
pad R39. A track has to be cut.
- If your board has a trimpot there then you can tombstone the pot and
add the cap.
- A 1K resistor across C107 helps.
- The leak is almost eliminated.