I have a transmitter setup from my router like shown below. The backplane is made from cardboard and has an RPSMA male wire held up in the middle. It is attached to my router.
Goal: design a monopole that can attach to the middle of this cardboard backplane and transmit a signal better than a simple 3.1 cm paperclip.
I am trying to design a monopole antenna that can attach to the RPSMA male pin in the cardboard through a female pin in this connector. It is the same on both sides.
The RSSI without any antenna using this setup is about -80 to -85.
I have a reference monopole antenna that is just copper wire of length 3.1 cm (the router is transmitting at 2.4 GHz so that is 1/4th wavelength).
However, unlike what I have seen online, the RSSI value only improves about 5 to 10 when this is plugged in. Either way, I expected using some sort of ground radials to improve this.
Using the shell of a motor and a soldering iron, I created this:
The main copper through the middle has an insulting layer of heat shrink tubing to stop it from conducting with the motor casing. It connects to my female SMA on the inside of the casing through the other side of the middle copper wire.
The 4 ground plane radials were soldered on, and they are also 3.1 cm wire in order to match the 1/4th wavelength.
Supposedly this is supposed to reflect the signal, however, this does no better than when the radials weren't there and it was just a plane copper wire. I assume I don't know something about the way ground planes are supposed to work. I was told any conductive radials would do the job but maybe they actually have to be grounded through the coaxial somehow?
This is my entire setup, and I'm not sure where specifically the problem is. My bet is on how I set up the radials, but that wouldn't explain why the improvement is only 5-10 in RSSI from no antenna to antenna.
Cross section of SMA: