Re: DDS Module is not functioning

William Kimber

Hi John,

If I can step in here.

First: The Ared voltage uses separate regulator as it is more stable and less noisy than the Arduino power supply. Set to 5v or slightly below, assuming Arduino powered at 5V..

Second: As you say anything requiring just relative measurements does not require calibration. Things like crystal or hi/low/bandpass filters. Return loss, stage gain/loss.  In fact many of the uses of the PHSNA.


On 12/12/15 10:44, jpking8@... [PHSNA] wrote:

Jim, Nick:

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 calibration procedure.

Thanks for the help guys.  This is probably the slowest build on record.

John, W5IDA

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