How do you start the SS quest? I've cleared out Hubris and grabbed the SS outfit and hat and for a while I was receiving a SS radio signal, but i don't seem to be receiving it anymore. Thanks.

Talk to the ghoul in the memory den in goodneighbor. He's in a room to the right of the reception area

When you first tune in to the Silver Shroud Radio, it should start off with a guy saying that all Silver Shroud fans should go to the Memory Den in Goodneighbor and talk to Kent Connelly. The rest of the radio is just a Silver Shroud Radio Serial, and while it's interesting to listen to, it can be ignored, as the initial dialogue before the serial starts is what triggers the quest itself.

Also, the Silver Shroud Radio is like most other radio stations: it's got a limited range, so you have to be near it in order for it to show up for selection in your pip-boy. If you're not hearing it, head to the eastern section of Boston until you get it again, then tune to it long enough to get Kent's call. After that, as I said, you can turn it back off and go to Kent to get the quest moving.

Thanks for your help!

Remember to speak as the Shroud when given the opportunity.