Re: More questions

 

I dreamed up a work around for Allards CW mod with mine!

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!

Raj


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.

Jerry, KE7ER


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.

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