Richer-R RK560 Portable Frequency Counter Meter 50MHz-2.4GHz - Handheld Radio Frequency Tester for Two-Way Radios, Baofeng Walkie Talkies - Ideal for Ham Radio, CB Radio, and Wireless Communication Testing

Tried to use to measure RF frequency from an old wireless garage door opener. The opener (RF source) had to be placed less than an inch from the RK560 Frequency Counter to produce any reading at all. And when it did produce a frequency reading, it was useless, because the indicated frequency jumps randomly between widely different numbers once per second. The indicated frequency on the RK560 display jumped wildly and randomly anywhere between 120 kHz to 250 kHz.The same garage door opener showed a rock-steady frequency readout on an older frequency counter which I have unfortunately lost. The remote still works with the garage door, confirming that the remote itself is functional (i.e. it is putting out a good RF signal).That means the problem is with this Richer RK560 Frequency Counter.For my purposes, this is a useless product. I cannot tell what frequency is actually emitted by my garage door opener. (The intention was to fine-tune it, to improve wireless range).