Testing SSTV Reception on Vertical Antenna Without Doppler Correction

I was testing SSTV (Slow Scan Television) reception from International Space Station using my vertical antenna without Doppler correction. In the frequency display you can see that it is static at 145.800 MHz, the nominal downlink frequency of SSTV transmission from ARISS. Signal strength of the audio as well as that displayed as number of segments below the frequency can be seen as varying as the satellite moves across the sky. Ideal method would be to use a directional cross Yagi antenna pointed in the direction of pass with live tracking and Doppler correction for the velocity of the satellite. Suboptimal method of reception has affected the picture quality. As I do not have an antenna rotator, I was trying with my vertical antenna rather than my Moxon Yagi. As it was the first attempt, I thought I will try without Doppler correction. During the next pass of ARISS I am planning to use Moxon Yagi and Doppler correction, to see if the reception is better. I was directly feeding the audio from the radio to my mobile phone with Robot 36 app in PD 120 Mode. PD 120 mode is meant for pictures sent over two minutes while PD 180 is meant for pictures sent over three minutes.