I wonder if damage to a circuit board or other component would account for the declining accuracy? The reason I asked about damaged equipment earlier is because my experience has shown that unserviceabilities like cracks or impacts from rough handling do not always stop something from functioning, but will degrade performance. Muzzle blast, heat from the sun or improper handling may cause problems.
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Steve, good question. The crystal oscillator is only as good as the components that control it.
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Capacitors and resistors can change values with age which will change the total output and accuracy of the circuit, and transistors due to the NPN or PNP junction also decline in response time with age. They just start getting erratic until finally giving up the ghost. So you can have all kinds of errors introduced due to voltage changes and/or bias changes to both the oscillator and the output circuitry. It’s common.
They state that accuracy is +/-.5% of measured velocity or better. For example, a 3000 fps load would be no more than 15 fps out. Say, 2993 to 3008 fps.
Steve, in the example of +/- .5% of 3,000 fps, the actual range of velocities displayed could be from 2985 to 3015.
Good shootin'
-Al
Oehler just happens to give you all of that.
![[Linked Image from i.postimg.cc]](https://i.postimg.cc/WbtbQ1Rt/191-FE29-D-4-FAF-411-C-AFF5-6-A30742-EE7-DB.jpg)
Ummmm.... I don't think so.
A crystal oscillators frequency is controlled by the physical dimensions of a little piece of quartz, that acts like a very high Q resonant circuit. With some effort, you can "pull" the frequency a bit, but that is on the order of 1 part per 1,000, not enough to matter in this case. If the bias isn't right, the oscillator stops. It doesn't shift frequency. Unless you are running the transistor very hot, or doing reverse breakdown, transistors go practically forever, and if they do fail or degrade, the oscillator stops. Solid state crystal oscillators either work or they don't. Most broadcast receivers use a synthesizer referenced to a crystal oscillater. You don't see those frequency drifting.
Just wild speculation: Maybe they cheaped out and used an LC oscillator rather than a crystal. The cheap way to do it is with a capacitor and a slug tuned inductor. With repeated vibration, the slug can come loose, and without the slug, the frequency of the oscillator goes up, and with it, the indicated bullet speed. If the slug works its way farther in, the opposite happens. That's a bona fide SWAG for you. If that happens to be the case, it's a poor design.
