It didn't take police long to trace the number and listen in on boasts to his girlfriend and other acquaintances about the crimes.

During one monitored call, he told his girlfriend: "Well, they want to know how dangerous I am, and if I pull knives and axes then I'm that dangerous."

The 20-year-old Vincentia man looked far less dangerous yesterday as he sat in the dock of Wollongong District Court to hear Judge Paul Conlon sentence him to six months' jail. Wighton had pleaded guilty to two charges of armed robbery.

The first robbery took place on March 17, when he phoned Eagle Boys Pizza about 8.20pm and made an order, giving a false name and the address of a house in Shoalhaven St, Nowra.

The occupant of the house told the delivery woman they did not place the order and, as she returned to her car, Wighton emerged from hiding wearing a hooded shirt and holding a knife.

She handed over $230, then Wighton ran away.

On May 22, he again used a false name when he placed an order with Pizza Bella and gave an address in Elizabeth Dr, Vincentia.

When the pizza delivery man found no-one home, Wighton approached him armed with a tomahawk and demanded his money belt.

The delivery man handed over $213 and the robber fled the scene.

Wighton later gambled the money he stole on poker machines.

Judge Conlon said pizza delivery drivers were easily categorised as vulnerable people and said the incidents would have been very traumatic for them.

"He has earlier told how he felt ashamed, sorry for his victims and his family, and I accept that as a genuine expression of his remorse," Judge Conlon said.

"Rehabilitation is important ... but the court cannot be blind to community expectations in a case of armed robbery where deterrence is important."

He sentenced Wightman to a non-parole period of six months' jail on each count, backdating it to the time he was first taken into custody.

Wightman will be released on December 9 and will serve an additional 18 months on parole after his release.