Gordon Hawthorn has admitted stalking BBC Points West presenter Alex Lovell and will be sentenced at Bristol Crown Court next year.
In an interview with the programme, Ms Lovell said she wanted to believe Hawthorn did not pose a threat.
But he had portrayed himself as a strong man who had previously raped women and was obsessive about Ms Lovell.
“These weren’t a couple of cards that came out of the blue, there were four years of cards before that, that were just filthy,” she said.
“Then suddenly there were these two years of the threats, that just got progressively worse.
“He would talk about how he was going to do it and it was very physical and so in my mind he was sexually aggressive, misogynistic, strong and frightening.”
Ms Lovell and BBC security teams contacted Avon and Somerset Police in January 2016, after the rape threats began.
Images of the greetings cards Ms Lovell had been sent were circulated, as well as examples of the handwriting inside them.
When asked if she ever believed officers would track down the author of the cards, Ms Lovell replied: “We all knew it was a real long shot.
“It was kind of frightening as well because I’ve got this image of a big bloke who could see this when it’s being shared and he could suddenly act out on all these threats, all these things he was going to do – that he’d been close, he knew where I was – so there was a real threat for me.
“I’m thinking ‘what’s going to be his reaction?’.
“It was a long shot but it was shared so much on social media and actually I’ve got to thank everyone that shared it because that’s how he ended up being arrested.
“It was just amazing that it came to that finally, to that conclusion.”
Ms Lovell appealed to other victims of stalking to “talk to somebody”, as well as to write about their experiences in detail.