From: Sverre Holm
Sent: 21. mai 2003 18:56
To: 'Steven Weber'
Subject: AT Sprint - DDS deceased?

Hi Steve,

I have now run SP and G on 40 m, PA and TA on 30 m, and UA on 20 meters with the 
AT Sprint. I am still amazed that I can put out such a strong signal from the tiny
final amplifier of this rig. Last night I modified the input boards with more diodes,
tested it on all bands, and fine-tuned the input filter. I brought it to the room
upstairs where I do radio operating, and then something wrong ... 

...

I am still investigating this, but so far it seems as if the DDS has given up. 
...



From: Sverre Holm
Sent: 22. mai 2003 09:01
To: 'Steven Weber'

...

My voltages are 11.9, 5.14, and 3.45. Notice that 5V is on the high side and 3.5V
is on the low side. The DDS has 0 Volts on pins 1, 2, and 14, indicating that set
up data has not been received.

My theory is that the difference between AVDD (5.14) and DVDD (3.45) is too large
for the AD9835, here it is 1.69 Volts. I hope I don't have the right datasheet for
the AD9835, but mine says Absolute max AVDDD to DVDD is in the range -0.3 ... 0.3 Volts.