Re: Sweep Response Results After Completing All Calibrations

Nick Kennedy

Hi Vince,

Frequency compensation should produce a reported value of 0 dBm across the full frequency range.  Is the output of your DDS connected directly to the log power circuit's input?  If so, you should be seeing 0 dBm.

The values in the provided file are more or less "place holders" .  It's possible they'd work with someone else's hardware, but not likely.  For one thing, my DDS puts out about +1 dBm actual power, but the standard build puts out about -10 dBm.

So I'd recommend going through the process of producing your own custom set of coefficients.



On Jan 21, 2015 1:14 PM, "n1vc@... [PHSNA]" <PHSNA@...> wrote:

I am performing the calibration procedure in Windows. Please see my question below:

I am calibrating from 1mhz to 30mhz and using -10dbm input to power meter:

1.      *Verified -10 dbm by looking at U1 pin 4 and it measures 1.846 volts. That is very close to the value stated on the schematic.

2.      * I did not zero the polynomials. I never changed them.

3.      * I then performed the slope/intercept calibration using a step attenuator and entered the new value in the txt file. Here is what I observed on the graph:


1mhz   -10 db                     30mhz   -12.8 db



1mhz   -10.2 db                  30mhz   -10.6 db

Maybe I am lucky, but I think these results look pretty good at least for my needs.

Question – I still don’t know what to do with the polynomials????

Please advise,

Vince N1VC

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