Old receiver

Dear all,
I have just finished to setup my first drone, but I have some doubts about my rc receiver. I am using an old one I had since a lot of years, but when I tried to setup the receiver fail safe parameter, I noticed that when I turn off the transmitter, the receiver does not go down to a stable pwm value, but gives random values. So I am worried that if it happens when flying, the pixwak will not detect it as a loss signal. Does anybody have experience about this issue?

Hi gents,

just for your information, I have found the problem: the receiver works properly, but when I was testing I was very closed with my laptop and the signal of the wifi was making it crazy when disconnected from the transmitter.