Weird Troubleshooting Experiences
- One time we did a complete radio installation in a small twin. Back in the 80's the radios still used crystals to tune in the various the frequencies. (Now Phased Locked Loops PLL do a better job).
After the installation was complete, when we transmitted on one radio it could be heard in the other, even though the interlock wire was in place. (An interlock shuts one radio receiver off while the other was transmitting)
This drove us nuts for a while until someone got the idea to switch out the main crystal in one of the radios.
Low and behold this solved the problem. The crystals were so evenly matched that they influenced each other.
Weird but true !
- War bird takes off and after about 30 minutes in flight, other pilots report nasty noise during radio transmission.
Even switching to the other radio did not solve the noise.
Once on the ground I checked everything over, but could not duplicate the problem.
We ran the engine up, which is quite a procedure for a war bird, and still no noise.
Even checked noise with an oscilloscope thinking it was coming from the generator.
On a hunch, while the engine was running I crawled up on the wing and reached in the cockpit and wiggled the radio selector switch while the pilot transmitted, and while wiggling the switch the noise happened !
Could it just be a bad switch ?
The switch looked like it was original equipment so I ordered up a new one that would fit in the existing hole and low and behold it solved the problem !
When the aircraft was in flight there was enough vibration to hamper the contacts inside the switch.
Weird but true !