Ok, I did a few tests:
I connected all the pins of the receiver (gnd’s and 5 v) but that didn’t change anything.
Then I replaced the antennas with my thick antenna wires for thinner ones: the reception was worse.
Then I cut of the antenna of the sender and now I have a much better reception!!!
Now I have a good reception but this is strange isn’t it?
Without a sender antenna I have reasonable good reich but I don’t like this “solution”…
Has anyone ideas for a better solution?
Here a image of my transmitter an receiver (now I cut off the senders antenna):