Why am I measuring decreased voltage between my dryer's neutral and hot conductors?
There is a problem with the neutral wire.  I would start by making sure the screw in the breaker box to the dryer's neutral wire is secure, and that the wire is mechanically intact by firmly wiggling it at the neutral bar end.

Also, the neutral bus in the main breaker box should be bonded to ground&mdash;usually by a green screw like this:


Check the bonding screw by unscrewing it a turn or two and then screwing it back in well.  If this is not in a service breaker box, but an auxiliary panel instead, there must be no neutral to ground bond.

If the breaker end checks out okay, then look inside the dryer outlet box.  (Turn off circuit breaker first.)  Those have screws to secure the house wire into the outlet.  Make sure the neutral wire (as well as the others) are mechanically sound and firmly attached to the socket.

If you measured the neutral inside the dryer, you should also check the appliance pigtail ("wall cord") for signs of wear.

If the ends of the neutral wire are okay, then it is time to measure the resistance of the wire from end to end.  Unless the dryer is located within leads span of the breaker box, you will need to scrounge up a piece of wire to extend the lead range.  It can be any gauge, but do measure its resistance so you can easily determine the additional resistance of the dryer wire.  The dryer's wires should be 8 or 10 gauge so the resistance should be very low:  100 ft (30 m) should be no more than 0.10 ohms.