I can confirm this approach works in practice, however one point is important -
If you turn off the K3S, but leave the KPA on, the discharge time will be at least ten minutes. I didn't bother testing after that. If you turn off the K3S, then turn off the KPA, then turn the KPA back on, it has full functions - OPER, band change, etc. This takes only a little bit of time. I did not observe a KPA band change to 60M though. Thanks Jack for taking the trouble of explaining what is going on. 73 de Chuck, WS1L [email protected] On Fri, Feb 5, 2021 at 6:57 PM Jack Brindle <[email protected]> wrote: > This bothered me a bit, so I took a good look at the source code and did > some testing. my results may be interesting. > > Chuck’s description with the K3S Not connected to the KPA are correct. > When nothing is connected to the band lines, they are pulled high inside > the KPA500. In the two radio modes that rely on BAND inputs, this would be > an invalid band (1111) and not allow the amplifier to go into OPER mode. > Chuck is correct here in that switching to either analog or serial mode > will allow the operation he desires. > > But, there is another choice. When the KPA500 is in one of the BCD modes > (RADIO = K3 or BCD), and the band signals indicate a valid band, then the > KPA will go into OPER mode and should work properly. > Now, how can this happen with a K3 or K3S attached? The K3/K3S has > resistive pull-ups on the band signals, so the signals are pulled up to Vcc > when they are not driven to ground. Vcc is the 5V regulated power bus in > the transceiver when it is powered. But when the K3/K3S is powered off, the > 5V rail will sink to the 0V level as the capacitors bleed off. That means > that the band signals are actually pulled to 0V (ground) a short time after > the K3/K3S is powered off. This combination defines a valid band, and if > the KPA is set to K3 or BCD modes, the amplifier will actually switch to > the 60 meter band. It will also go into OPER mode if you tap the OP button. > > So, the alternative solution is to leave the K3S attached, power it off, > wait until the KPA500 switches to 60 meters, then you can switch the KPA > into OPER mode, switch the input to the alternate rig, and start operating. > > 73! > Jack, W6FB > > > On Feb 5, 2021, at 5:12 AM, Chuck Chandler <[email protected]> wrote: > > OK, I've figured out the problem. I took a step back and realized I am > spoiled by the close integration of the K-Line. The reason the FT101 can't > key the amp is because, unless the K3S is turned on, the amp won't leave > STANDBY mode. > > Even with the AUX cable disconnected, the amp sits in STANDBY and pushing > the OPER-STBY button doesn't do anything. I guessed a menu setting might > control this, and setting the KPA Menu item RADIO to ANALOG now allows me > to switch bands and from STANDBY to OPERATE via the KPA front panel buttons > with the K3S turned off. > > A quick test shows 25 watts of tube-generated CW gives 450 watts output. > Looks like I'm in business. Just need to change the menu item when I > switch radios. > > Many thanks to all for the help! > > 73 de Chuck, WS1L > > [email protected] > > > On Fri, Feb 5, 2021 at 7:12 AM Chuck Chandler <[email protected]> > wrote: > >> Just tried it out - AUX cable removed, RF Input cable removed, RCA plug >> with clip leads inserted in PA Key. Shorting the leads does not put KPA in >> TX. >> >> 73 de Chuck, WS1L >> >> [email protected] >> >> >> On Thu, Feb 4, 2021 at 6:54 PM Jack Brindle <[email protected]> wrote: >> >>> That is good. If you plug a pig-tail RCA jack into the KPA’s PTT input >>> and short the wires, does the KPA go into TX mode? If so, the issue is in >>> the transmitter or the cable you are using. >>> You should do this test with nothing connected to the KPA’s RF input. >>> >>> As i noted in my post to the reflector, Fred Cady’s book has some very >>> good info about this. Now if I can find it in my electronic copy... >>> >>> 73! >>> Jack, W6FB >>> >>> >>> On Feb 4, 2021, at 3:47 PM, Chuck Chandler <[email protected]> >>> wrote: >>> >>> Hi Jack >>> >>> It’s a Yaesu FT101ZD, and my multimeter shows it closes continuity >>> between the key line center and shield on TX. >>> >>> No grid block keying! >>> >>> Chuck >>> >>> On Thu, Feb 4, 2021 at 18:37 Jack Brindle <[email protected]> wrote: >>> >>>> Chuck; >>>> >>>> What is the PTT output from your other radio? It needs to be just >>>> open-circuit, pull to ground on transmit. If anything else (I’m thinking >>>> grid-block keying), then I predict a trip back to the factory for your KPA. >>>> >>>> There are two key lines coming into the KPA, and going through the KAT. >>>> These are the AUX I/O PTT, and the RCA-jack PTT. They are maintained >>>> separately through the Kat on their way to the KPA. Either can key the >>>> KPA500, and both are opened by the KAT when it has high SWR or needs to >>>> tune. The AUX I/O version is only meant be used with Elecraft rigs using 0 >>>> - 5 signaling. The RCA jack is likewise meant to be used with rigs that >>>> only pull the signal to ground on transmit, and leave it open on receive. >>>> >>>> Thus my question - what i the signal characteristic of the rigs PTT >>>> output? >>>> >>>> 73! >>>> Jack, W6FB >>>> Elecraft Engineering >>>> >>>> >>>> > On Feb 4, 2021, at 2:15 PM, Chuck Chandler <[email protected]> >>>> wrote: >>>> > >>>> > Just a follow-up to my question about using the KPA500/KAT500 with a >>>> > second, older radio. I just finished some more testing and found >>>> that when >>>> > I remove the AUX cable from the back of the KPA and try to put the >>>> KPA into >>>> > TX with the keyline, it stays in RX. >>>> > >>>> > A continuity tester confirms the rig keyline is closing when the rig >>>> is in >>>> > TX, and the KPA shows driver power output, as does the KAT. But, the >>>> KPA >>>> > won't switch to TX and amplify. >>>> > >>>> > Is there some other function keeping the KPA in RX even though the AUX >>>> > cable is disconnected? >>>> > >>>> > 73 de Chuck, WS1L >>>> > >>>> > [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] >>>> >>>> -- >>> Sent from Gmail Mobile Chuck Chandler [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]
