On Mon, Nov 11, 2024 at 11:11 AM, Neil Preston W0NRP wrote:
Is there any practical way to make a VNA that provides the same measurements
over the frequency range of ~10 Hz to maybe 1 MHz?
I have seen articles describing ham use of, and there are commercial versions of, UPconverter/DOWNconverter products for using low(er)-frequency VNAs to measure higher-frequency and even waveguide components.
All of these, however, use a sample of the analyzer's local oscillator with which to lock the up/downconverter.
Perhaps some clever ham could devise a hack to do the reverse, DOWNconvert the VNA port 1signal with a mixer and after passing the resulting audio frequency signal through the device being tested, UPconvert the AF signal using another mixer and the same LO and feed it to VNA port 2. Likely some filtering and/or image-reject mixers would be needed. I am not certain whether correct phase relationships would be preserved going through the mixers, though.
Another problem would be that the IF filters in the VNA may be too wide for audio use; there may be software workarounds for this.
73, Don N2VGU
Donald S Brant Jr