I am getting a reading of 442 MHz at -66 dbm, 251 pW. it fluctuates between 200 pW to 315 pW. By accident I discovered when I grab the meter with my thumb and finger at the front of the meter, the signal stops. Any thoughts as to why that happens? There are other readings in the table mode such as 858 MHz, 802 MHz, etc but they don't stop, just the 442 reading.