Hardware details.
pa0nhc 20170403

        LET OP:
For other Arduino compatible boards then i used, program file "sweeper.txt" must be changed (definitions of board pins). My PCB design is not useable.

The 9851 DDS board (2x 10 pins) works on 180MHz clock frequency using a 30MHz oscillator cristal (Fclock = 6x Fxtal).

In my version Arduino software, in the comman string for the DDS, the fith byte is "00001". The last (multiplier) bit is "1". The 6x multiplier of the 9851 chip is switched ON.

If a DDS board with a 9850 chip is used (with on it osc.Xtal = ClockXtal = 125MHz), the multiplier bit must be "0", to prevent burning out the DDS chip.

        Detector diodes .
Only especially for RF detection developed germanium diodes are use able. I used N270.

Also use able are : AA143, 1N34A, 1N60, 1N100A. The value of R7 and R11 then probably must be adapted.

Cheap addresses for 1N270 germanium RF diodes :
AliExpress, Banzai, Amazon, Ebay, op-electronics.com

IMPORTANT : Only when D1, D2, D3 en D4 all four have the exact same properties, the temperature drift will be minimal. Order 20 pieces and :

Select (with the help of a DIGITAL ohmmeter) four best matching diodes (all four the same diode-test-reading).

    Correction possibilities :
My values for R7 en R11 (2k2) were experimentally found.

If your SWR1, SWR2, SWR3 en SWR7,8 graphs have not the correct position, two correction possibilities exist :

1. If you used 1N270 diodes, then correct the number in the software line "SWR=SWR*1000 "
2. If you used another type diodes, than firstly correct the values of resistors R7 and R11.

I designed a double sided system board. It should give the best results at high test frequencies. For easy change of of R7 and R11, drill theit holes a little bit wider.

Double sided system board - 69,342mm x 58,674mm

        You could also build this SWRsweeper
- on a single sided (bottom copper) PCB. Green (top copper) tracks must be replaced by wires.
- As a dead bug construction on a piece of blanc copper ground surface.
    Star with the BNC and R1,2,3,C1,D1. Keep mass connections ultra short.