Keying a LA-1k with a Yaesu 991A
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I've been successfully using my LA-1K for a couple days manually keying it with a switch, but that gets a little old/quick, especially when doing digital modes on EME/MSK. From the?users manual/diagrams showing it driving a Yaesu amp, I ass-u-med the FT991 would be able to directly key the LA-1k as well.? I hooked up a known good keying cable to the LIN/TUN jack that I'd borrowed to test it while waiting for?mine I ordered to arrive.? Unfortunately, immediately upon power on of the 991, it enabled transmit on the amp, prior to keying the transmit function on the radio. Upon troubleshooting, I discovered the LIN/TUN keying circuit on pins 2&3 have continuity 100% of the time, regardless of the menu 143 settings/values. It's definitely NOT functioning as expected/intended.? I did speak with the person I borrowed the cable from and he assured me his 991(s) supply a ground return only upon activation of transmit on that cable, regardless of the tuning menu selection (internal/external/etc). He typically uses this very cable to drive his VHF amp or a transverter, so I know the cable is not shorted. What am I missing?? Is their high current draw and/or any special keying requirements on the LA-1k that I’m not seeing here? Thanks in advance, 73 Tim W5TRL ————————————- 73 Tim W5TRL Phone/text 512-799-0308 |
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Folks- I got my answer(s) already....? ?I posted this query to the group yesterday and it just appeared tonight.? Regardless....? ?The Palstar keying current is 20 to 25ma, well within the 200ma limit that Yaesu states the TUN/LIN TX GND signal will handle. However, Yaesu Tech support told me today that they've seen extraneous RF come into the TX GND circuitry previously and cause the switching transistor and/or associated diode(s) to fail and provide a shorted TX GND signal mode in 991s.? ?Usually caused or aggravated by the use of an unshielded keying line.?? So, 6-7 weeks from now and $75-100 later I should have the 991 back, only with shielded cabling and an isolating/buffer accessory... Thanks, 73 Tim W5TRL On Thu, Apr 1, 2021 at 9:13 PM W5TRL via <w5trl.tim=[email protected]> wrote:
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Tim.W5TRL