Re: Response Sweep PHSNA Checkout

Nick Kennedy
 

Wow, that's super jumpy.  Your AD8307 circuit has good stable output to the meter.  But the PHSNA is giving erratic readings ...

As a first check, I'd input some DC voltages <= 5V to the PHSNA box using a solid DC supply and pot.  It might be hard to generate a constant slope, but if you set it to various values, you could see if the software gives stable readings.  Or try one (1.5V), two (3.0 V) and three (4.5) AA cells in series to the input and see what you get.  Measure the voltages and calculate what dBm readings you should be getting.  Are they close?  And stable?  If not, it's in the PHSNA somehow.  If so, it's in the AD8307 circuit or somehow in the interconnections.

73-

Nick, WA5BDU

On Sat, Dec 13, 2014 at 6:43 PM, lh1907@... [PHSNA] <PHSNA@...> wrote:
 

 I'm using Nick's standalone windows program located in the Windows PHSNA folder to checkout PHSNA using Type II AD9850  The windows/Arduino file versions are PHSNA.exe (Ver 1.35) and PHSNA_VB.ino (Ver 1.3).  The Calibrate DDS and Slope/Intercept Setup/Calibration procedures checkout fine. After completing the Slope/Intercept Calibration, I ran an uncompensated Response Sweep over 10-40 MHz frequency range. The dBm spread of data points is too large.
 
 See the graph (UncompensatedResponseSweep.gif) in W2HHV PHSNA Type II Checkout folder. This approximately 8 dBm peak variation in a data point is also observed when the display dBm function is selected. This variation (about 0.4 VDC for the existing slope) is not observed at power meter or Channel 0 ADC input. The +5 VDC reference is a steady level at AREF Arduino input pin. I changed the 2 ms delay in report_adc() function of PHSNA_VB.ino file to 4 ms and there is no change in Response Sweep results. The average frequency response is fine since a 5th order, 27 MHz, Cauer LPF is installed on the PHSNA board.
 
 Windows 7 Home Premium is the PC OS.
 
 Any ideas on where to look next?
 
 Larry, W2HHV


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