[Elecraft] KE7X KX3 Book and Configuring: KX3, K3, KPA500, and KAT500

Wed Apr 23 09:58:28 EDT 2014

Good morning all.
Sorry I haven't chipped in before.
I think Jack's comment "...something else going on..." is right on.  

The band line pull-ups in the K3 are somewhat problematic.  They weren't there in the first placed (which was good design) but were added to the K3 early on to compensate for band decoders that didn't have pull ups (not good design).  So that explains why the KPA500 shows 5.3 MHZ when the K3 is turned off.

However, neither of the key lines from the K3 (KEY OUT and KEYOUT_LP in ACC, K3 schematic of June 2010) are pulled up.  One is an open drain and one an open collector.  These two lines are wire-ORed together in the KPA500. Wire-OR means either KEY OUT or KEYOUT_LP or both can key the KPA500. So I don't think that is what is causing the behavior you see.

I don't have the KX3 in the mix here at the moment but I tried the following:

K3 on 15 m, KPA on in Operate mode showing 21 MHZ.
Turn K3 off.  KPA switches to Standby immediately and then shows 5.3 MHZ a second or two later (significant delay there).
K3 still off. KPA switch from Standby to Operate and back and forth no problem.
K3 still off, KPA in Standby. Ground the KPA keying line PA KEY.  KPA can switch to operate and back and forth no problem.  When in Operate the * shows on the display as expected (saying the amp key line is low).

Another culprit might be DIGOUT1, although that too is an open collector output.  I wouldn't expect that to be doing anything when the K3 is off but if you see a _ in the KPA display, that means the amp is inhibited when you try to key because INHIBIT in enabled and DIGOUT1 is low.  

Firmware: K3 4.83, KPA 1.38

What is your firmware?  There was a firmware change in the KPA a while ago that fixed a power up problem.

Cheers,
Fred

> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
> Phil Hystad
> Sent: Tuesday, April 22, 2014 11:35 PM
> To: Jack Brindle
> Cc: elecraft; don at w3fpr.com
> Subject: Re: [Elecraft] KE7X KX3 Book and Configuring: KX3, K3, KPA500,
> and KAT500
> 
> Jack,
> 
> Thanks for the detailed explanation.  So, if the K3 pulls the keyline
> to ground and the STBY/OPER switch is inoperative as a result, then why
> would power cycle on KPA500 change things.  I mean, I assume that the
> keyline is still pulled to ground by the K3.  But, I admit that I am
> not an electronics guy as you others so I do not fully understand all
> of the stuff that goes on in these things.
> 
> 73, phil, K7PEH
> 
> 
> On Apr 22, 2014, at 10:18 PM, Jack Brindle <jackbrindle at me.com> wrote:
> 
> > 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 <phystad at mac.com> 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 <w3fpr at embarqmail.com>
> 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 <w3fpr at embarqmail.com>
> 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.
> >>>>>>
> >>>>>>
> >>>> ______________________________________________________________
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> >>>>
> >>>
> >>
> >> ______________________________________________________________
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> >> jackbrindle at me.com
> >
> 
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