KPA inhibit SWR? The KPA500 uses Reflected Power for all of its protections except for one item - if the SWR is above 18:1, it will throw an immediate fault. There is no adjustment for these thresholds. As far as the Auxbus, the KPA does not listen but only talks on it, conveying band, mode and power on/off status. The KPA gets its band data from the K3 using the BAND lines. The KPA always does a frequency count of the input signal, and will change bands if the count indicates a band other than what was expected. And yes, we have seen instances where parasitics from a transceiver triggered the band change. It turns out they were much higher in amplitude than the fundamental frequency. I don’t remember the transceiver manufacturer, but it was not an Elecraft.
The KAT500 has adjustments for SWR for tuning requirement. I don’t recall any others, but there may be. The manual should state them. The KAT does listen to the Auxbus, getting frequency info. As you know, if the calculated SWR is above the threshold, the KAT will disable the PTT signal to the KPA, and if in the AUTO mode, it will initiate a tune. Because of timing differences with measuring forward and reflected power, we do not recommend leaving the KAT in AUTO mode, especially for SSB transmissions. One other thing to consider is that the KAT has an internal bypass, which leaves the KAT Ls & Cs in-line, which is separate from the front-panel BYPASS mode, which completely bypasses the Ls and Cs. Also, if the KAT sees too much power at its input when it starts a tune, it will add a resistive pad to lower the power it sees so that it does not hot-switch the relays. I hope this helps explain what you are seeing. I wonder if you have the two thresholds spaced too closely. 1.4:1 and 1.6:1 are awfully close for calculations. Also, I would be really interested in hearing more about the loop antenna you are driving, along with the coax feed, and all connectors. We see an amazingly large amount of problems in the KAT & KPA due to issues that are actually in the antenna system. 73, Jack, W6FB > On Jan 1, 2024, at 6:46 PM, Jeff Wandling <j...@w7brs.com> wrote: > > Thanks. That's good detail. I'll recheck the manual once more. I made a > common mistake of assuming too much and not reading enough. I have > tremendous respect and faith in the engineering put into the system of the > Elecraft line.. That's a long way of saying, It works brilliantly. > > I just want to avoid a mistake in where the ATU-500 and KPA-500 are trying to > resolve a tune whilst the CW spews forth. > > This comment and the prior comment about the Kenwood aspect (and related > command-set mentioned) are interesting. Thanks. > > Aside from all that -- when folks here use the "SWR Thresholds" and use the > K3+KAT+KPA chain via Aux Serial data sharing -- what do you use for the three > metrics in SWR Thresholds? > > There's a KPA Inhibit SWR, Re-tune SWR and Bypass SWR value. The > recommended values in the manuals seem frightfully high for my nerves to > handle. > > Any advice on *that* would be welcomed. > > HNY, Thanks. > > --- > 73, Jeff W7BRS > https://blog.w7brs.com <https://blog.w7brs.com/> > > > > On Monday, January 1st, 2024 at 4:37 PM, G4GNX <g4...@g4gnx.com > <mailto:g4...@g4gnx.com>> wrote: > > >> AFAICR the manual says that if an AUX cable is connected between the KAT500 >> and the radio, the KAT500 will follow any frequency/band change and if a >> tuning solution has already been stored for that frequency/band it will be >> employed before the radio goes into TX. In other words, whilst the radio is >> still in RX mode. >> >> However, elsewhere in the manual it says that when the KAT500 receives RF, >> it will also pickup the nearest tuning solution, which is a fail-safe action >> in case the KAT500 does not receive data from the radio, for any reason. >> >> This is only if the radio is a K3, K3S or K4 and if a KPA500 is in use, RF >> from it is sent to the KAT500 but the AUX cable must be connected AFTER the >> KAT500. i.e. K3———KAT500———KPA500. >> >> I make no comment about using the KAT500 with a Kenwood (or other) rig. >> >> 73, >> Alan - G4GNX >> South Coast UK >> Elecraft K4D / KPA500 / KAT500 / IC-9700 >> >> >> >>> On 1 Jan 2024, at 21:56, Andy Durbin a.dur...@msn.com wrote: >>> >>> "> How does your KAT500 know what frequency to use? Does it have a serial >>> data interface or does it depend only on the internal RF counter? >>> >>> W7BRS> AUX cable between K3 to KAT-500 and KAT-500 to KPA-500. They are in >>> serial communication per Elecraft protcol(s), whatever those are. >>> >>>> What KAT500 mode (AUTO, MAN, BYP) is selected when you observe this >>>> anomaly? >>> >>> W7BRS> Per manual for KAT-500/KPA-500 the stated "nominal" mode is MAN. So >>> I leave the KAT-500 in MAN after tuning the antenna to 1.1." >>> >>> Your problem sounded a bit like the conflict between serial data frequency >>> and RF count when operating near a "bin" boundary. However, my only >>> experience with that problem is with Kenwood rigs using serial data to >>> provide frequency to KAT500. I have no experience with AUXBus. >>> >>> For Kenwood owners one solution was to use the FDT command to desensitize >>> the RF counter so serial data frequency always had priority. The command >>> description implies it is equally applicable to AUXBus so may be worth >>> experimenting. >>> >>> "FDT Frequency Counter Distance for Retune >>> GET format: FDT; >>> SET/RESPONSE format: FDT nn; where nn is the distance, in kHz, between the >>> current ATU frequency and the most recent TX frequency count for the ATU to >>> change ATU settings to the new frequency. The value is between 0 >>> (interpreted as the default of 10 kHz) thru 65535, which disables ATU >>> tuning based on frequency count. This is intended for customers that prefer >>> the KAT500 only follow the frequency provided by a serial port command or >>> the K3/K3S/K4 AUXBUS, or select a minimum distance between current ATU >>> frequency and a newly counted frequency. >>> FDT was introduced in firmware version 01.99." >>> >>> Andy, k3wyc >> >> >> ______________________________________________________________ >> 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 j...@w7brs.com <mailto:j...@w7brs.com> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > <http://mailman.qth.net/mailman/listinfo/elecraft> > Help: http://mailman.qth.net/mmfaq.htm <http://mailman.qth.net/mmfaq.htm> > Post: mailto:Elecraft@mailman.qth.net <mailto:Elecraft@mailman.qth.net> > > This list hosted by: http://www.qsl.net <http://www.qsl.net/> > Please help support this email list: http://www.qsl.net/donate.html > <http://www.qsl.net/donate.html> > Message delivered to jackbrin...@me.com <mailto: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
