While it may be true that antenna gain doesn't go negative, you will still see physically small antennas with a gain of less than 1 dBi. I have seen as low as 0.25.
Why ? Because the whole device itself is so small.
However, there are some very nice tiny ceramic antennas, with a decent amount of gain. See Johanson Technology for some examples. We used them for Bluetooth and they were great performers.
Yes, I think you have it. But just to be clear, when you say the receiver can be negative, are you saying the receive antenna or the receive signal?
The receive signal can be negative, but the receive antenna cannot be negative.
Thank you again Eric, yes I meant received signal. As I understood received antenna will be positive as it is antenna gain along with the transmit antenna.