Stumped by radio near cave

[mythmaker]

Ren has told me to tune my radio near the three rock piles at the cave entrance. I hear rapid morse code around 98. At the first pile - the radio turns bright red - but nothing happens. I have tried each tick around 98 and still nothing happens. What am I missing here?

[Sunsetter]

You're not looking for the morse code, just turn it until you see a shaft of light from the cave and weird noise.
(as far as I remember)

[mythmaker]

Thanks. Frustrating when you don't know what to look for!