Thought I would finish off this thread and let you know
how things have come out at long last. The amount of time
required is largely due to my very limited shop time,
which I hope to improve on next year.
As the main unit sits now, I am consistently getting
output from the main board. It does require a push of the
reset button on the screen of Nick's Windows program to
get the output started. I understand that is normal
behavior. RF output is constant in power up to about 7
MHz, then falls at the rate of about 6 dB/octave out to 60
MHz. This is consistent with the AD9851 frequency range.
The fall rate is linear when expressed in dB with no large
variations in rate.
In the end, it appears that there were two problems
causing the original concern. The first problem was the
requirement for a jumper to cause serial mode data entry
to the AD9851. The second issue was apparently with a bad
solder joint somewhere on the main board. I resoldered
everything so I can't really say where the fault was.
Jim asked at one point if any of the traces had
deliberately been cut on the main board. The answer is no
and the two places on the board indicating the possibility
of a cut do show continuity.
In any event, it works and I'm now happy.
I do have a couple of questions, if one or both of you
would be so kind as to answer them.
First,there is an R17 variable resistor on the main
board that appears to set a voltage for Aref, pin 30 on
the Arduino. What voltage should this resistor be set
for and what is its function?
Second, I think I remember that Jim said in one of his
posts that he had never gotten around to calibrating his
power meter because it was not necessary for the way he
used the PHSNA. Is that the case, and what uses did not
require calibration? I am thinking they were probably
relative power output readings over a fairly narrow
frequency range, resulting for example from measuring a
crystal filter response. If so, I may also delay the
Thanks for the help guys. This is probably the slowest
build on record.