Thank you gentlemen for the comments.
Had looked for years for available video or tapes w/o success on how to operate a yelper. There could be some now. I just tracked down several well know 'yelper' call makers and picked there brains for a couple of years. Even took several road trips that were well worth it.
Suction calls are not properly operated by sucking on them. Learning to control the draw, as you draw in air across moistened lips is key. A little similar to making a squeak or rodent squeal to attract a yote using your lips. Once you get the gist, you are ready to move forward.
I can't cover all the pertinent information here. There is much -much more. Please feel free to contact me if you have any questions.
The major draw back of suction calls is that irresponsible and rookie hunters have ended up hunting me on numerous occassions. Wasn't pleased once when two guys tried to sneak up on what they perceived as a hen, while having one of my young twins with me. When I stepped out of the blind, they knew what was up as they left in a hurry w/o me saying a word. Yes, I know that the human voice is the safest, but I let emotions take-over.