I'm very new to shortwave listening and just got to grips with my RTL SDR HF dongle. Last night while on the 20m band, there were signals exactly every 50kHz, starting exactly at 14.000MHz, then at 14.050 MHz, 14.100 Mhz and so on. Google said they may be my power supply. Today I wanted to troubleshoot them but they are mostly gone, making me even more curious to what they could be as I have exactly the same electrical equipment on today.
Here's a close up of the one that was at 14.200 MHz
The SDR is connected to a very simple wire dipole with a 1:1 balun. One end of the antenna is attached to the top of my two storey house but the other end is much lower down, attached to a metal gate (but via insulated dog bone connector).