Here is my version of a "squealer" for an audio output from the R2LC. It consists of an inverter/level shifter and a 555 timer chip. The frequency range isn't really broad, but it is enough to hear changes of RF signal strength. I am also using my meter in voltage mode for a digital readout via wireless video. The loudness potentiometer is 500 ohms. The battery's positive terminal (via a switch) is connected to Pins 4/8.
I needed an acoustical baffle for the rear of the speaker, so I just decided to stick the circuit board inside the a truncated pill bottle that had already donated its closed end to another project. It is powered off the 9V battery I am using for the R2LC.
I wanted to swap out the Harbor Freight meter for one with display illumination so that my video camera's image would be clearer, but wouldn't you know it, HF didn't have a single one in stock yesterday! When I go to Camarillo Wednesday, I will go to the main HF headquarters to pick one up.
So now my configuration is complete - test receiver, squealer, meter, wireless video, and a 'scope and one of my Track Signal Strength meters to monitor the output of the Base.
Now what was I going to do with all of this.....?
Dale, so was this a rhetorical question? That is, have you tried using the squealer to some effect?
I did wire up a squealer to the R2LC but to Elliot's earlier point, it is not "calibrated" in any absolute sense so you can't hear a pitch and translate it to "good"... not that there is/was any claim that it is anything more than a relative (getting warmer, getting colder) tool. What I noticed is if the pitch changes, even a few seconds later the brain (mine anyway) has no memory of what the pitch was 10 seconds ago. Obviously with the digital readout, one can just see it was 35 or whatever and after some fluctuation see that it is 35 again and be confident the signal strength is what it was.
So ignoring "talking" digital meters that speak the measurement, what more can be done using audio or any other indication method to provide a better tool for troubleshooting? In an off-thread message Elliot suggested perhaps a limited number of pitches might be easier to interpret ... similar to red-yellow-green.