Hello George,
when using AP mode the module is working on the WiFi Channel 1. This mean that if there is any other device on this channel, they will interfere with each other.
So please make sure that there is no other (the best is when it is on Channel 4 or higher).
If you are using a radio that has telemetry support, it could interfere with the Wifi - for this reason placing antennas of the receiver or module by 90° in other position may solve the signal quality completely.
Other issue is that if you will install the module in the helicopter frame, the signal may be not strong enough. But usually this is not the case as the module has powerfull transmitter.
For setting the password for the AP, you can do so in the AP Settings menu directly in the web interface of the module (
http://192.168.4.1).
There you can set the Encryption and password.