The TV is likely not emitting any information, but rather just noise. A TV from the 80s would have been a CRT set. These work by sweeping a beam of electrons through a raster scan. The aiming of that electron beam is accomplished by subjecting it to a controlled electric field, and as we know, radios are machines for detecting electric fields.
Since the raster is scanned at a regular rhythm, you are most likely receiving signals at the same frequency as the horizontal scan, or some multiple thereof. It looks like PAL scans 625 lines, 50 times per second. So the horizontal sync frequency is 625*50 = 31.25 kHz. It is probably approximately a triangle wave, so you will also find harmonics at every odd multiple: 93.75 kHz, 156.25 kHz, 218.75 kHz, and so on.
The intensity of the electron beam is further modulated as it scans the display, and so multiplied by the 31.25 kHz line frequency can generate frequency components into several MHz, depending on what's being displayed on the TV.
Lastly, if your HackRF antenna is very close to the TV, you may be overloading the receiver, causing clipping and associated harmonic distortion, which will in effect create copies of signals at regular intervals throughout the spectrum. A CRT produces a very strong electric field with very little current, which is why they don't radiate noise very well far away. But up close the electric fields can be very strong (that's why they attract your hair).
