Hallerb has described why electricity should not be coming from coax
- if properly installed. That coax earth ground is required by code.
Yet many installers either don't know or don't bother to make that
earthing connection (that should also connect to breaker box ground).
A house built in the 60s or 70s may not have that earthing ground - may
only use a cold water pipe. Therefore cable and AC electric may not be
sufficiently bonded together. Visual inspection is required - this
cannot be measured.

AC electric voltage might be coming from safety ground of AC
recpetacle. For example, if receptacle safety grounds are not properly
connected to breaker box, then even another shorted and dangerous
appliance could put AC electric on that satellite receiver dish. There
could be many possible sources of dangerous voltages coming from that
AC outlet - if safet ground was compromised. We strongly suspect one
thing. Unacceptable AC voltage is probably on the AC safety ground.
A voltage that may (only may because we only have a subjective shock -
no numbers) trip a circuit breaker if safety ground is then properly
connected to breaker box.

That three prong tester would confirm a missing safety ground.
Tester can detect defective safety ground, but tester cannot confirm a
safety ground is properly installed. Appreicate the limits of that
tester.

wrote:
I agree it should be grounded immediately before the coax enters your
home and the grounding block should be unified with your main house
ground. for a long list of reasons not all are, and this is helped by
grounded plugs on all new receivers