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Antenna SWR measurement

Posted: Sun Nov 19, 2017 5:14 pm
by Cryptlabs

I would like to measure the SWR of an HF antenna.

I have everything setup and working.

How do i connect the HF antenna to the RP ?

I'm using this app :

I also have the

Thanks in advance :)

Re: Antenna SWR measurement

Posted: Thu Dec 21, 2017 10:30 am
by izsurk

you need additional hardware. By its very own nature the bare red pitaya can only measure signals which go through a device under test (DUT). To achive this goal the DAC creates a waveform (sine) which then passes the DUT and is the measured again (using the ADC). This is what's called a insertion loss measurement (sometimes states as S21 in scattering parameters). You could do this measurement too, if you had two antennas. Parctically this measurement won't tell you anything unless you are in a well defined RF environment (RF lab).

But I think you are interested in measuring the match of the antenna to 50R right? So your goal is to measure S11 (which can be converted to VSWR via basic math). For this you need something called: "directional coupler", "return loss bridge" or "reflection bridge". Basically it is a device which will kind of isolate power which is reflected from the DUT and present it to the RP. Should cost around 30$. You won't need a special one for the frequency range of the RP. Google for it, there are tons of homebrew ones around the internet.