There appears to be some misconceptions in this discussion. First, the information flow from the K3 to the KPA only occurs on the band lines and the key line. Auxbus communications is one-way, from the KPA to the K3. The KPA does not listen on the Auxbus.
There is also something else going on that is in play here. When the K3 is powered off, the pull-ups on the band lines (and the key line, I believe) continue to work. They continue to pull the lines to Vcc. But with the K3 off, Vcc is now 0 volts. This means that a short time after the K3 powers off the KPA will see all zeros on the band lines, and will switch to 60 meters. After this, RF coming into the KPA will cause it to switch to the appropriate band, and all band switching will occur with incoming RF as long as the band lines do not change. Of course, there is one other signal in play here. The Key line is important since it causes the KPA to switch into transmit. We have seen the K3 pull the Key line to ground at times, which just may be what you are seeing. If the KEY line is active, the KPA will not switch from STBY to OPER. For this to happen the KEY line must be high. The best way to connect two transceivers to the KPA is to use a physical switch to select the transceiver. A five-pole two position switch will do for the band and key lines, plus a coax switch of the RF. In short, you may get things to work with the description from Fred’s book. But if the key line becomes driven low by the “off” transceiver for any reason, you can expect weird things to happen. Jack Brindle, W6FB Elecraft Engineering On Apr 22, 2014, at 5:04 PM, Phil Hystad <[email protected]> wrote: > Don, > > OK, I may be expecting too much. Actually, I am not sure if I was expecting > as much as I was a little bit surprised by the behavior. I didn't think that > the KPA500 and KX3 communicated with each other other than RF and Key line > but maybe that was enough of a difference from the K3. The K3 of course in > my case has the AUX cable connections with the KPA500 and KAT500. > > It is not a big deal as long as this is the way it is expected to work. I > was not sure if I had done something wrong or not. > > But, just picked up W1AW/5 MS QRP power with the KX3. Actually, it was about > 6 watts. > > 73, phil, K7PEH > > > On Apr 22, 2014, at 4:57 PM, Don Wilhelm <[email protected]> wrote: > >> Phil, >> >> I think you may be expecting too much. >> Consider a parallel - a computer communicating with a printer. If you >> suddenly switch the printer cable to another computer, would you expect the >> printer to continue printing without any intervention? >> >> The "printer" in this comparison is the KPA500 and the two "computers" are >> the K3 and the KX3. >> >> It is not unreasonable IMHO to expect that a reset of the KPA500 would be >> required. >> >> If the KPA500 were simply an amplifier with no communications capability >> with the driving transceiver, switching from one source of RF input to >> another should proceed without regard to whatever is the driving device, but >> your KPA500 is more than "just an amplifier" because it can communicate with >> the K3 or KX3 driving transceiver. Expecting the KPA500 to switch data >> streams from two different transceivers with no intervening reset is not >> realistic. >> >> 73, >> Don W3FPR >> >> On 4/22/2014 7:41 PM, Phil Hystad wrote: >>> So, is this normal behavior? I wasn't expecting any kind of comms between >>> the K3 and the KPA500 that affects the STBY/OPER switching. It does seem >>> that a power on/off cycle for the KPA500 is required to enable that switch. >>> >>> Is this designed to work this way or is this a flaw in the design or maybe >>> a missing mini-feature of configuring two different transceivers with the >>> KPA500. I admit to not scouring all of the documentation yet on the >>> expected functionality of the STBY/OPER switch. >>> >>> 73, phil, K7PEH >>> >>> >>> On Apr 22, 2014, at 4:14 PM, Don Wilhelm <[email protected]> wrote: >>> >>>> Phil, >>>> >>>> Let me get this straight - the KPA500 is communicating with the K3, then >>>> you switch to the KX3 and the KPA500 does not talk with the KX3. >>>> >>>> If that is what is happening, I would expect that to be the case. The >>>> communications with the K3 is not synchronized with the attempted >>>> communications with the KX3, so a reset (power cycle) of the KPA500 may be >>>> required. >>>> >>>> 73, >>>> Don W3FPR >>>> >>>> On 4/22/2014 7:02 PM, Phil Hystad wrote: >>>>> Some follow-up questions: >>>>> >>>>> OK, I have the KX3 and K3 configured with the KPA500 and KAT500. >>>>> Everything seems to work with one little exception. >>>>> >>>>> The exception: >>>>> >>>>> --- initial conditions, K3 is on and switched to use the KPA500 and >>>>> KAT500. KX3 is off. >>>>> >>>>> --- using K3 and so on works fine with amp on or with amp in standby. >>>>> >>>>> --- I turn off K3. Leave KPA500 on but in STBY mode. >>>>> >>>>> --- Switch coax from K3 to KX3 (1x2 switch). >>>>> >>>>> --- Turn on KX3. KPA500 still in STBY mode. >>>>> >>>>> --- Attempt to switch KPA500 to OPER from STBY but switch does not >>>>> work. If I power off the >>>>> KPA500 (front panel switch) and power back on then switch works >>>>> fine. >>>>> >>>>> I have experimented with all kinds of starting initial conditions and >>>>> order of events but whenever >>>>> the KPA500 is left on after using the K3 and then switching to the KX3, >>>>> the switch on the KPA500 >>>>> to go from STBY to OPER does not work. I always have to cycle the power >>>>> from the front panel on/off >>>>> switch. >>>>> >>>>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:[email protected] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [email protected] >>> >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
