With all the various pieces of information in this discussion, let’s answer things correctly. First, is hardwired cabling needed? The answer is no, it is definitely not. The KPA500 always counts the RF frequency and will switch to the counted band if it does not agree with whatever else it sees. If the input frequency from a cable says 10 meters, but the counted frequency is for 15 meters, the amplifier _will_ switch to 15 meters. This is to make sure that we are always on the band for which RF iS coming in. So, is there any advantage to having the hard-wired cable? Yes, a slight one. To answer this, let me explain how the band switching occurs. When the amplifier detects, and confirms that RF is coming into the input port on a band different than what it was last using, it will institute a band change. This causes the KPA to drop out of amplifying, then switch bands, and then re-enable amplification. This takes 17 milliseconds to accomplish. What this means is that you will lose a portion of the first CW character. If you were sending a W, you will get a shortened dit. If you were sending at high speed, you might end up with an M. Considering that this happens rarely (just on band changes), you probably won’t object to the shortened dit (or dah). Note that the count is always verified (at least two valid counts must match as I recall).
So, what is the recommended usage? As I note, it works with a cable, or without. You just need the PTT input connected to the transceiver so that the KPA knows when to go into transmit. Can there be problems with not using a frequency cable? The KPA does a remarkable job of protecting itself. You don’t want to make a habit of transmitting into the amplifier at 100 watts, or you could damage the front end protection. But, in general it works just fine without problems. So, what do _I_ use? I have the very first KPA, and another that is a couple of years old. I use a K3-compatible band cable with my amplifiers. The biggest reason is that I am constantly testing my amplifiers (even while using them in a contest), and want to make sure everything is working just fine. After more than ten years, no problems. I do test them without the cable at times as well.In general, when you hear me in a contest, it is with the cables in use. Thus, both ways work great. If you try it without a band cable and are troubled by the shortened dit, then build (or buy) a cable. Otherwise, just enjoy the KPA500. We worked very hard on the protection circuits and processor code, and it does a very good job of taking care of itself. 73, Jack, W6FB > On Mar 22, 2022, at 4:24 AM, F5vjc <foxfive....@gmail.com> wrote: > > What is the advantage of using a band switching cable between the > transceiver and the KPA500 over just relying on the RF sensing function? > > I want to drive my KPA500 from an FTDX 101D, is a cable the better way to > go? > > 73 F5VJC > ______________________________________________________________ > 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 jackbrin...@me.com ______________________________________________________________ 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
