N2PK Standalone VNA - SVNA

The N2PK Standalone VNA (SVNA) is based on a design by Lawrence, VE7IT. To see Lawrence's adaptation of the N2PK VNA PCB to a standalone, reflection only, VNA with its own controller and user interface, click here.

Here are some of the changes that I made to Lawrence's design:
  1. RFIV Test Head instead of a T1-6T bridge and the bridge type is software selectable to be one of: RFIV test head, matched Hi-Z bridge, Lo-Z bridge or T1-6T bridge.
  2. Soft power control where the toggle switch in the pixes below was later replaced with a pushbutton. This also includes an inactivity shut-down to conserve batteries and a low voltage shutdown to preserve accuracy (and batteries).
  3. Provisions for transmission measurements including group delay.
  4. Internal smart battery charger.
  5. 5V switcher to conserve batteries and minimize internal heating.
  6. Coax cable parameters.
  7. Search a user specified frequency range for minimum SWR
  8. Code updates to support these and other changes.
A rather unique test configuration is used for transmission measurement with one detector. This configuration places the transmission DUT (T.DUT) between the RF DDS and either the RFIV Test Head or a matched Hi-Z bridge which is, in turn, connected to the detector RF Input.

With 50 ohms as the reflection DUT (R.DUT), the transmission DUT sees a nominal 50 ohm load (as needed) and the RF DDS provides the nominal 50 ohm source impedance. At the same time, both the RFIV Test Head and the matched Hi-Z bridge provide relatively low insertion loss with the 50 ohm reflection DUT unlike the T1-6T bridge which is balanced with the 50 ohm reflection DUT present.

For reflection measurements, a coax jumper is used between the RF DDS and the RFIV Test Head input. This coax jumper is also the transmission thru calibration standard.

The above configuration and other features of the N2PK SVNA can be seen in the following block diagram:

Click to enlarge
(The block diagram can be enlarged for better clarity by clicking on it in an 800x600 window or larger.)

N2PK SVNA Photo Gallery

Here are some pixs of my N2PK SVNA (click on each to enlarge):

If you're still reading and interested in more, click on each document or ZIP file named below to either view or download it:
  1. N2PK SVNA Schematics (Ver. 1, 110 KB)
  2. N2PK SVNA Software (Ver 1f, 227 KB)
Note that these schematics are untested since there have been NO builds directly from them yet. Verify pinouts etc against other sources of info. Use at your own risk!


Please feel free to contact me with any comments or questions at:


Paul Kiciak, N2PK 

URL: http://n2pk.com/SVNA/SVNA.html
Last updated: 20 September 2010
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