If you have a different opto, try that. Or try reducing the resistance. The
opto will switch more reliably then. I had a problem like this one time and
reducing the resistance to increase the opto's LED current helped. Don't
know about the RFI.
Jerry W4UK
At 09:35 PM 2/8/2002 +0000, Glenn VanBlaricum, W6KNB wrote:
>As usual, a few hours before a rtty contest, I'm trying once again to
>solve an RFI problem.
>
>I've been using identical resistor/transistor circuits to key both the PTT
>and data line to my FT-1000. On 40 meters at power levels above about 200
>W, the circuits lock on until I dial down the power. This doesn't occur on
>other bands.
>
>I thought I would try optoisolator circuits instead, so I wired up a 4N25
>with an input line 1.2 k resistor only to discover that while it seems to
>switch state when the input is toggled, the resistance in the output
>collector-emitter is too high to switch my transceiver. I measure about 40
>ohms in the "on" state for the optoisolator, but the transistor circuit
>shows only about 3 ohms and works fine with the transceiver. I tried 4N33
>optoisolators with the exact same results.
>
>Has anyone experienced similar problems and found a solution? Obviously
>the real solution is fixing the 40-meter RFI, but the antenna match is
>pretty good, I have the coax coiled near the rig, and I have ferrites on
>every line in sight. Any ideas?
>
>Good luck to all in the WPX later. I'll be there, just with not much poop
>on 40 meters.
>
>Glenn W6KNB
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