Unusual power variations in GPS signal on 20 – 21 June

Timing seems to match with the planned strike to Iran [1]. Wonder if there's some longer term time series on the data, maybe correlated to world events?

[1] https://www.theguardian.com/world/2019/jun/21/united-airline...

Are these measurements difficult to make? IE: could I monitor it myself from my location, with an SDR for example.