Forced air helps keep "hotspots" from happening, though even with forced air there can be some. Auto-turners help keep the user from being tied so closely to the incubator. Care needs to be given that the turner is monitored to be sure something doesn't happen and it stop turning....just pay attention when you look it that the eggs have indeed changed position. Getting all of this for under $100 isn't going to happen unless you find a super deal somewhere or a good used one....it looks like one sold yesterday in the BST forum...you might want to monitor those forums.
Here's a list of three different ones:
GQF 1588 Genesis w/turner (quail and chicken) @ $162.10 plus shipping from Cutlersupply...good quality styrofoam, digital thermostat, forced air (fan), turner has racks for both chicken and quail, large "picture window" viewing, capacity is 42 eggs (if I recall correctly). The digital thermostat seems to be doing an excellent job.
GQF 2362 Hova-Bator w/turner (quail and chicken) @ $121.95 plus shipping from Cutlersupply. Good quality styrofoam, analog (wafer) thermostat, forced air (fan), turner has racks for both chickens and quail, twin smaller windows for viewing, capacity is 42 eggs (IIRC). Wafer thermostat isn't as precise as digital, but millions of birds have been hatched with this type of thermostat.
Brinsea Octagon 20 ECO w/turner @ ~$150.00 while on sale from
www.brinsea.com . Hard plastic. From folk's reports this incubator holds temperature and humidity a bit better than the GQF styrofoam incubators but at the expense of half the hatching capacity.
Best wishes,
Ed