Dan: The PC-P3-K3 connection is used because the P3 gets frequency, IF bandwidth, RIT offset and other data from the K3 very frequently. Logging programs also require a PC connection to the K3. Hence the need for the "daisy chain". The P3 passes command / response data through from one serial port to another, adding its own command / response stream to the P3 to K3 part of the "chain".
The KPA500 gets band data from the K3 via the band change lines on 15-pin ACC connector. The KPA500 communicates its band switching preference to the K3 via the AUXBUS line of the 15-pin ACC connector, so that the K3 changes bands when you press band buttons on the KPA500 front panel. None of the K3/KPA500 integration uses serial ports. There's no need or advantage to daisy chain the serial port. The KPA500 does not "pass thru" commands and responses between the two serial port connectors, as you have discovered experimentally. The KPA500 uses its XCVR serial connector for firmware load, configuration save/restore, fault analysis and remote control of the amplifier; these are functions of the KPA Utility. A serial port command set has been published that permits others to write KPA500 remote control software as well. As N1RX correctly stated, the KPA500's XCVR serial connector is for radios that provide frequency information via a serial port, primarily Kenwood. Band change information from the K3 isn't needed for the KPA500 if you don't mind that the first dit or "ahh" (or "hola") on the new band is shortened. When my prototype KPA500 didn't yet have band change via the parallel port, I'd just tune the radio to the new band, tap the paddle, and the amp was ready to go on the new band. My K3 to KPA500 connection consisted of the RF cable and an RCA connection between the K3's Key Out and the KPA500 PA Key connectors. I didn't connect ALC. This still works today. The ACC line connection between K3 and KPA500 does offer one additional operational advantage: The K3 retains two different power levels for each band, one for use when the KPA500 is in operation, and another when it's off. So I can set the K3 power level to transmit at 100 watts when the amplifier is switched off and about 30-35 watts from the K3 to the KPA500 when the amplifier is in Operate, and I don't have to remember to change the K3 power each time I turn the amplifier on. The K3 learns that the KPA500 is or isn't operating via AUXBUS communication over the 15-pin ACC cable. The amplifier keying connection and ALC line also go through the 15-pin ACC connection, which makes for a straightforward installation requiring just two cables between radio and amplifier, the 15-pin ACC cable and the RF output of the transceiver. I haven't played with ALC, I just keep the K3's power where it belongs. But the ALC connection is there. Some antenna tuners and SWR monitor devices offer a relay to interrupt the amplifier key line when SWR exceeds a threshold. If you want to use this capability, use an RCA connector keying line daisy chain from radio to SWR bridge/ATU to KPA500. The KPAK3AUX cable kit includes a small "key line interrupter" that looks like an DB-9 "gender changer" with a pin removed so that the key line from K3 to KPA500 through the ACC cable is "interrupted". The KPAK3AUX accessory connector cable option kit also includes an all-15-pins-connected Y cable so that you can concurrently connect additional devices to the K3's ACC connector. Some cables and Y connectors sold for VGA monitor applications do not have all pins connected "straight thru". I use a 4-port 9-pin serial "ABCD" switch box connected to an Elecraft KUSB USB-to-Serial Adapter connected to my development computer as "common", and the four serial port outputs from this ABCD switch go to one of two K3s, a KPA500, and a 3.5mm serial data cable that I plug into a W2, XG3, or K144XV, depending on what I'm doing. I may in the future add another layer of switching so that 3.5mm data cables can be connected to a W2, other products in development, and a free cable for use with the XG3 or K144XV. I use a KUSB rather than a multi-port serial PCI card because I need to very frequently test the various utilities through the USB to Serial adapters that Elecraft sells, and I use relatively long and convoluted RS-232 paths so that I develop and test with a less than ideal short direct connection. Absent this requirement, I'd use a 4- or 8-port PCI serial card like a "Rocket Port" and use USB to Serial adapters only when I had no other choice. 73 de Dick, K6KR -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Dan Atchison Sent: Saturday, July 16, 2011 7:13 AM To: elecraft@mailman.qth.net Subject: [Elecraft] [KPA500] Serial Port Connections on KPA500 Team: Now that I have completed my KPA500 (S/N 196) I have a question regarding serial port connections. I have the current, complete K-Line (K3, P3, KPA500). 1. Do I need to put the KPA500 in the serial port chain? After all, it does have a serial port goes-inna and goes-outta. 2. Is it really necessary? 3. If there are benefits, in what order should they be chained. 4. Then, what are the benefits? Reason I ask, I just did the following chain things are not working correctly. Serial port - P3 - KPA500 - K3. Obviously, I am missing something. Thanks, Dan ______________________________________________________________ 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
