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Texas Ranger SRA-FC393 Frequency counter drift

DaveEbelII

New Member
Jul 4, 2023
19
16
3
Glendive Montana
I've noticed after it's on a while it just starts randomly drifting from 27 all the way down to 25 MHz . It does this no matter what radio it's on ..
I don't suppose any of you fellers know of a solution for this problem?
 

That counter was designed to be powered from a radio's internal 9-Volt regulator. Packaging it in a plastic box invites folks to power it from 13.8 Volts or more. This overheats and degrades the 5-Volt regulator. That chip drops about 4 Volts when built into the radio. The drop will be twice that if it's powered from 13.8, and this doubles the heat load on the regulator chip.

Don't know which of several production versions is in your counter, but popping the cover and reading the output of the 5-Volt regulator when it does this could reveal the cause if it's dropping or showing quirky noise when probed with a 'scope.

A meter alone won't tell you if funny noise pulses are coming out of the regulator chip.

73
 
That counter was designed to be powered from a radio's internal 9-Volt regulator. Packaging it in a plastic box invites folks to power it from 13.8 Volts or more. This overheats and degrades the 5-Volt regulator. That chip drops about 4 Volts when built into the radio. The drop will be twice that if it's powered from 13.8, and this doubles the heat load on the regulator chip.

Don't know which of several production versions is in your counter, but popping the cover and reading the output of the 5-Volt regulator when it does this could reveal the cause if it's dropping or showing quirky noise when probed with a 'scope.

A meter alone won't tell you if funny noise pulses are coming out of the regulator chip.

73
It's brand new . I've only used the 5 volt jack on the back of three different radios with the same results.. sever drift after it's been on a few minutes.
 

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