Last year I had no luck in receiving the April ISS SSTV event, as the RTL SDR antenna I had back then turned out to be broken. John from South East Communication was kind enough to ship a replacement to me without having the ship back the broken one.
Until this month while Victoria is in lockdown that the 4-5 Aug ISS SSTV came up, which I would have no excuses to miss as I have to be at home while it happens.
The setup is very simple. I plugged my main 2m/70cm J-pole into the RTL-SDR dongle, via a SMA-Male to SO-239 adaptor. The RTL-SDR is then trivially plugged into my Linux laptop.
On the software side, I used GQRX and tuned to the downlink frqeuency 145.800 of ISS. The signal arrived so strong that I could simply widen the filter to account for doppler shift without jeopardising the signal quality. The audio is piped to the system audio sink, which will also be the input to QSSTV. This way I can see the image decoded in real-time. I also turn on recording in GQRX so I can decode later in case something is wrong.
In QSSTV, configure the audio output sink as input via Options > Configuration > Sound. Once it is configured correctly, you can verify QSSTV is correctly receiving the audio by looking at the volume indicator or the audio spectrum waterfall.