A GLASAIR PLT OFF RWY 7R HAS AN NMAC WITH A SENECA OFF OF RWY 7L 2 MI E OF DVT; AZ.

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DEER VALLEY ARPT HAS 2 PARALLEL RWYS THAT ARE VERY CLOSELY SPACED TOGETHER. OFTEN; DURING THE WKDAYS; ONE CTLR WORKS BOTH RWYS ON DIFFERENT FREQS. EVEN THOUGH DIFFERENT FREQS; THERE'S A 'PARTLY LIVE' EFFECT; WHEN YOU CAN TELL WHAT'S HAPPENING ON THE N RWY EVEN IF YOU ONLY HEAR 1/2 THE TWR CONVERSATION ON THE S TWR FREQ. BUT THIS WAS A BUSY WKEND; WHERE 2 CTLRS WORK EACH RWY SEPARATELY ON THEIR OWN FREQ (NO PARTY LINE). I HAD BEEN CLRED FOR TKOF ON RWY 7R STRAIGHT OUT TO THE E. APPARENTLY; A TWIN HAD BEEN CLRED FOR TKOF BEFORE ME ON RWY 7L; ALSO STRAIGHT OUT. NO ONE TOLD ME ABOUT THE TWIN; AND SO I WASN'T REALLY LOOKING FOR HIM. I DEPARTED RWY 7R; AND BECAUSE SDL CLASS D AIRSPACE IS SO CLOSE TO OUR CLASS D AIRSPACE; I STARTED VEERING ABOUT 10 DEGS TO THE N. WE HAVE A NEW TOY IN THE PLANE. IT'S A POOR MAN'S TCASII. IT WAS GOING OFF LIKE CRAZY; WHICH IS NOT UNCOMMON NEAR AN ARPT. BUT I WAS SCANNING ANYWAY; AND AS I LOOKED TO MY LOWER REAR L; I SAW I HAD OVERTAKEN A TWIN BELOW ME. YIKES! THANKS LORD. NO ONE IN THE TWR SAID ANYTHING OTHER THAN 'FREQ CHANGE APPROVED' (IT SOUNDED LIKE S TWR UNAWARE OF THE NEAR HIT) AND THEY WERE TOO BUSY FOR ME TO QUERY ABOUT THE TWIN. (FRANKLY; I DON'T KNOW IF HE SHOULD HAVE BEEN THERE OR NOT.) COULD HAVE BEEN A TRAINEE ON THE N TWR FREQ; AND NO COORD BTWN TWR CTLRS. (TRAINEES DON'T KNOW HOW FAST GLASAIRS HOMEBUILT ACFT ARE.) I WAS FLYING FROM R SEAT (FORMER CFII) WHICH MADE SEEING TWIN ON LOWER L HARDER. ALSO; EVEN THOUGH THE GLASAIR IS FASTER THAN THE TWIN; IT WAS ONE OF THOSE SLOW CLOSING SPD SITS; WHERE THE HUMAN EYE DOESN'T DETECT MOTION. HAVE RESOLVED TO SCAN N RWY FOR DEPARTING ACFT AS I TAXI INTO POS AND TO HOLD RWY CTRLINE BETTER FOR AT LEAST 2 MI BEFORE VEERING OFF.