I was playing solo when I picked up UA's.
I never attempted the SSS cos it was pointless when I was alone and in a viper.
So yeah, you can still get involved. I'm still going through WSS's.
I took on many Strong Signal Sources both in an Asp (bascially unfit for that) as well as in a Python (dedicated heavy-duty setup to handle SSS).
The best I found in Strong ones was an AI Relic setup as bait for 3 Anacondas - managed to swoop it right under their noses
Still, nothing we'd be looking for, just standard stuff.
Same with USS or the Weak ones - all generic stuff.
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Hint for surviving Strong Signal Sources in ships that aren't made to normally enter them :
Note that after entering them, there's always some delay before bad guys spawn (1-5 sec, Open Play might have higher delays).
Use that delay to kick Afterburner immediately after entering (what momentarily might be empty space or only i.e. some bait Canister(s) ).
Regardless of what will spawn there - it'll do so at low ship speeds, while you're already at max. speed, ready for a fast retreat and quickly out of the dreaded <2km range where Vultures/Anacondas/Pythons/FdLs can quickly reduce the Ship's Shields to rubble.
If there's no Canisters floating around, no reason to stick around anyway...
If there are Canisters - all their content is displayed conviniently in the Contacts Tab, so no need to point the Ship's nose at them while bad guys spawn around.
That trick kept even my 5D-Shielded and unarmed Explorer Asp in good shape every time.
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My general observations from my own tests looking for it :
My priority was the area ~500LY to ~1000LY from civilization, as that's the "not so normal/everyday" area of Signal Source spawns.
In the elevation levels of +150 to +250 (above galactic plane), with X-orientation towards the Galactic center, I got just about zero Signal Sources. 1 Weak one after many hours of traversing that area and scanning tons of Objects.
In the elevation levels of -150 to -300 (below galactic plane) however (X-orientation towards the distant Phantom Streak Nebula), those spawns were occuring
far more often for some reason.
Might be nothing, but to me it was something I definitely took note of (and I didn't expect that).
If that means anything indeed AND what we're looking for is "seeding" or "scanning" suitable Planets - it might come from below the galactic plane rather than from above.
To me, it would make sense if "they" basically followed the same goals as we do - search for suitable Planets and candidates for future expansion/resource-rich Objects.