Spektrum servo compatibility with Arduino

We are currently using our Spectrum H6040 Digital high speed servo motor for our system with Arduino Duemilanove board, and the speed from the specs is 0.08 sec/60 deg at 6V, but when we tested sweep arduino program, upon changing the delay per step to 8ms (delay value of 8), the servo was jerking a lot, and not acting the way the sweep program is asking it to do. Any idea why it's not working? We had used a Hitec servo (doesn't say it's digital) of spec of 210ms/60 deg (3.5ms/deg) and it was fine with the sweep program.

The Spectrum servo performed according to the sweep program when the delay value was above 8ms. Any ideas on why this is doing this?

Thanks a lot.

Killer servo! Are you using an external power supply for the servo? That one will pull a lot of amps; likely more than the board can supply.

I used an external power supply (a voltage regulator from Dimension Engineering but any 4.8v - 6v battery or supply would work). I tied the ground to the ground on the board. I am not running such big servos, but I am running a lot of them. Here is a thread where I show some of what I have done. http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1265626147/6#6

Changing the delay to 8 might not have the result you expect. The servo library only sends refresh signals to the servo every 20mS. So multiple servo writes in that time period will be ignored (except the last one)