Radio Operator, Wo/AG, Wireless Operator Designations?

Why were there so many varied Radio Operator positions in the RAF and USAAF?
I have found RAF Observer, Radio Operator, Wo/AG, Wireless Operator (Air) designations?
The USAAF had most if not all these plus Assistant Radio Operator...

Were there special qualifications and training for each?
Were there much more complicated Radio equipment in some aircraft that required a specially trained person in the position of Radio Operator or...?

Granted the Wo/AG had also qualified as an Air Gunner. So I assume he ran between the two positions as needed.
What was the difference between an RAF Radio Operator and an RAF Wireless Operator?
===> The Brit word for Radio is Wireless <===

USAAF Special Operator must have been associated with Radio Jamming Operator. Correct?

Photo from the article at: http://commons.wikimedia.org/wiki/File:Lancaster_wireless_operator_WWII_IWM_CH_8790.jpg
IWM caption : Flying Officer R W Stewart, a wireless operator on board an Avro Lancaster B Mark I of No. 57 Squadron RAF
based at Scampton, Lincolnshire, speaking to the pilot from his position in front of the Marconi T1154/R1155 transmitter/receiver set.

 

You can add to this the SO (Special Operator) for ABC Cigar devices.

 

Call me old-fashioned(and not a Brit), but Wireless Radio was the old "morse code" utilizing the telegraph key.(which you can see in the lower right of the photo). "Radio" radio, would be that utilizing direct voice communications. I would think that it took some extra training for a wireless operator to get good at sending and receiving Morse transmissions.

Just a word of advice - never send faster than you can receive.

 

The AAF had one basic MOS for radio operators on aircrews: 757 - Radio Operator-Mechanic-Gunner. There was an MOS 2756 - Radio Operator and Mechanic, but I've never run across an aircrew member with this MOS. All R/O were also trained as gunners. Only on lead crews was the R/O at the radio console for the entire flight, and these men were still MOS 757. On normal crews, the R/O also manned a gun, on B-24s usually either the nose turret or a waist position. Spot Jammers, etc. were also MOS 757.