HC12 Limited range

I have been able to transmit with my sensors from an Arduino UNO to another UNO using the HC12's. I have set the AT8 command for highest xmot power level but can only get about 7 feet before it looses connection. I am only using the stubby wire antennas. Is there a better antenna (specific model please) that will work with these units or am I doing something wrong?

I eventually have to have my sensors transmit from outside the house to the display inside. Will these work?

I also have the 2.4GhZ (NRF24L01's) units but cannot get those to work at all.

Any help would be appreciated.

There are clones on the market.
First check if the modules are exactly the same.

Shouldn't have to use max power or different aerials.
The modules should do at least 1km at low bit rates line of sight.
Leo..

Yes they are. They both are the ones with the white silkscreen and logo on it.

Please read the "How to use this forum".
We can't properly help you without knowing all the details.
Leo..

If you are using the helicals then make sure there is no metal near them, such as wires , metal box etc, as they detune very easily.
If that doesnt work, then try 17 cm of straight wire soldered to where the helical goes.

Thank you, I’ll try that. Like I said, they do work and one does transmit to the other, but if I separate them more that 7 to 8 feet, it stops talking.

Mauried, Thank you again for your suggestion. The 17cm Wire helped significantly. I can no go from outside through a glass sliding door into 20 feet in the house and still get reception. I can work with this.

A helical shouldn't be much different from a 17cm wire at that distance, unless the helical isn't made for 433Mhz.
Did the "stubby wire antenna" (post#0) come with the HC-12 modules?

These modules output 100mW, so you should use a properly tuned aerial.
Not doing so could overheat or even fry the transmitter output stage.
Leo..

Yes, the stubs antennas came with it, but the range was terrible. So not sure what else the issue could be.