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Hi All

I think I know the answer to this but before I actually do it can I have confirmation from someone who either knows or at least fully understands the circuit better than me.? I don't want to damage anything.??

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I want to key my Juma PA100-D amplifier with my QMX.? The Juma T/R signal is to ground the tip of the plug.? My understanding of the QXM is that it has +5V and active-ground options on its PTT with active-ground on the tip.? So do I just wire the interconnect lead tip to tip and screen to screen, ignoring the ring?? Then the QMX active-ground grounds the Juma T/R input and the amp is keyed?? (I normally use KX3 which is ring to tip so it looks like I can't use the same interconnect lead).? I also recall some posts recently about the need for an intermediary FET switch rather than keying an amp directly?? Does that only apply if the changeover relay is getting its power via the keying line?? The Juma has a relay changeover but the power for the relay presumably comes from the amp itself rather than the keying line from the QMX if that's just acting as a switch to ground?

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Hopefully its a quick thumbs up and I can make the lead.? I'm planning to use it in the SKCC WES this afternoon testing a prototype UMPP mini straight key I've been developing over the hols.?

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Thanks and 73

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Peter GM0EUL?

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Right, so, after a whole afternoon spent doing a 5 min job I finally got this to work.? At first it just wouldn't work no matter how I configured the firmware for the PTT.? After a bit of testing I decided it must be a problem with the socket itself and, whilst looking for the schematic and assembly manual online to try and troubleshoot, I re-discovered that there is a mistake on the early boards that needs a jumper across the socket to work around.? Grrrr.? Did the mod and immediately the grounding to the tip on tx worked!? Then there was a problem keying the amp because the QMX QSK is so much faster than the amp's relay that it kept tripping the SWR protection as soon as I tried anything over about 10wpm or any character with two consecutive dits.? I always use full QSK and my KX3 copes with it so I wasn't sure what to do.? The I remembered the QMX has a semi-QSK option and tried that.? It immediately worked fine and I was able to work Martin EI3LG in Dublin running 80w.

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73

Peter GM0EUL

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