>I'm running an older borrowed K3 to get various I/O issues worked out >while awaiting arrival of my K3S. I am interfacing the K3 into an older tube >amp with large open frame relays for antenna IN and OUT. The maximum >TX DELAY limit of 20 ms on the borrowed K3 is not enough to avoid hot >switching the amp output relay contacts. I had the delay in my old >FT1000MP set for 30 ms which was adequate with some margin (it had a >max delay of 40 ms I believe). Are there any options in newer K3's for >more than 20 ms of TX DELAY? Hopefully the K3S will have more than 20 >ms or my options for QRO are QRT. . hi. 73. . . Dave, W0FLS
If I remember correctly, Wayne said that 20ms was as far as he could stretch the TX delay without major changes in the firmware. There is no particular reason to expect that to have changed in the K3S. Also, K2AV is right in saying that one shouldn't expect a modern transceiver to neutralize all the problems of the older generation of amplifiers. The cure for that is to update the amplifier to modern standards. However, it isn't always necessary to modify the amplifier for full QSK if you don't personally require that facility. In some amplifiers, there is also a simpler solution that will probably work with the K3 in non-QSK modes. The circuit referenced below will reduce the switching time of a typical open-frame relay by roughly 50%, bringing the typical 30ms delay down to about 15ms which the K3 can handle. In practice, you would simply set TX DLY in the K3 to 20ms, allowing a little extra time for contact bounce. As well as speeding up the RF changeover relays, the circuit also updates the amplifier's PTT interface to the modern "industry standard" of +12V at a few milliamps. <http://www.ifwtech.co.uk/g3sek/in-prac/best-of.htm#speedup> The circuit is fully described in the referenced magazine article (click "April 2002"). 13 years on from the original data of publication, it has earned a good track record. Obviously such a simple circuit cannot magically provide full QSK with slow open-frame relays, but for "the rest of us" it can be a very useful update for older HF amplifiers. It also works well with coaxial relays for VHF. 73 from Ian GM3SEK ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
