RF Checker with LTC5505 - LTC 5505 and Arduino

Hello, I need to check RF level signal present between 300Mhz and  450Mhz, up to 20 or 30 meters from the transmiter device, I have to use a 3V Coin Cell like power supply.
I have selected the LTC5505 device to do that.
I want to connect the Vout to an analog input of Arduino UNO and show the signal level present by display
I have already the prototype pcb like the typical circuit as shown in the pdf datasheet file, to test the system, But, I have a few doubts
1* - The selected device(LTC5505), is the best option for this project?
*2 - What is the right value of the capacitor connected to the RFin pin to check this range of frequencies?
*2 - I have connected a random value capacitor and 16,5cm antenna printed in the pcb, I receive signal, the Vout pin changes the value when the RF signal is present, but the distance between the 1 Watt transmitter and my prototype pcb is 30 cm,  more away this distance I can't receive signal. Why?
*4 - When I receive the RF signal, the Vout pin changes the value, but the value goes from 25mV to 1,5V in a peak of voltage when the transmitter start to send RF signal and falls down to 25mv inmediatally, even when I keep transmiting. why the voltage level does not keep in 1,5V?
Thank You!

[edited by: Eugeniomercol at 12:20 PM (GMT 0) on 4 Feb 2019]