"I am Alpha and Omega" - Theses first and the last letters of the Greek alphabet were used to declare that God has always existed. In Isaiah 44:6 we read, "I am the first, and I am the last; and beside me there is no God." There is no doubt that the language here implies absolute divinity and could not ever be applied to any OTHER than the only true and living God.
There is, due to a difference of reading in the Greek, an inability to know absolutely if in this first use - here in Revelation 1:8 - it refers to Jesus Christ. In this particular verse we are reading about God the Father or simply God.
The phrase Alpha and Omega is used five times in scripture, all in the Book of Revelation. Also note the term, "the beginning and the ending" is only used twice in scripture and both in Revelation and both with "Alpha and Omega." Interestingly enough, it does appear that God is sometimes referred to as the speaker who uses the term, but more emphatically we cannot escape the fact that Jesus is also called the Alpha and the Omega here in Revelation.
It seems that the Holy Spirit is completely ignored in the Book of Revelation in terms of ontological description but is only spoken of in terms of speaking. What is intriguing is the phrases that were once used exclusively for God in the Old Testament are now, in the Book of Revelation, being extended to Jesus. It shows that these descriptions now also given to Jesus as evidence that the Man Jesus, born of a woman and born under the Law with the fullness of God present in Him, receiving all that the Father (His Father) has, and as mediator between God and Man, obtaining the titles of Alpha and Omega, the beginning and the end, the first and the last, whereas these terms were not assigned to Him during His walk through mortality. In other words, He now reigns as the One who was, and is, and is to come, the Alpha and Omega of all things, and our access to the Almighty. It difficult to see that the Holy Spirit is a co-equal, co-eternal, third person of the Holy Trinity - come what may.
I am more and more beginning to see God as becoming flesh, filling the Man Jesus, the Man Jesus revealing Him in the flesh, doing what His Father would do, overcoming this world, and the Man Jesus being given all that the father has and reigning until the end where He will submit Himself to God, step aside and God will become all in all.