Can I use a nanoVNA to align a TV aerial?

[Chris Wilson]

Google suggests I can but I don't see how it would work as the VNA is basically a transmitter, so how can it show a received signal peak as the aerial is moved? Thanks If it can be done could some say how, or link to how please?

[jwet]

Yes- VNA's measure not only reflection but also transmission.

The most common configuration for a VNA is in reflection mode- S11, etc.  Reflected voltage/Incident Voltage measured with a single port.  The other common operating mode is transmission mode (two port mode) where you measure the ratio of Transmitted voltage to Incident voltage - S21.  The second port is a Receiver and acts similarly to a spectrum analyzer with a few wrinkles.   S21 as displayed is the ratio of received voltage on port 2 to incident voltage on port 1 and this is a vector ratio (it accounts for phase). With your antenna, you won't connect port 1 to anything (terminating it would be best).  The s21 ratio will be zero everywhere except where you get a a signal from the antenna.  You'll get an amplitude that is greatest when the antenna output (s2 voltage) is greatest, ignore the phase, it will be meaningless- its not driven from the signal generator.  You can derive how good a spectrum analyser this makes.  Its only OK since you're not making a ratiometric measurment, there is a small IF offset, the dynamic range isn't great and bandwidth and resolution isn't what you would typically want but it will work.  It will give you signal strength after a fashion.  A spectrum analyzer like the Tiny SA would be a better tool for this.  There may be a way to just readout S2 voltage on the Tiny VNA but its not in the menus- this would make it a bit more like an SA.  Will the PC software allow this?- I don't know.