at least ten minutes. I didn't bother testing after that.
it has full functions - OPER, band change, etc. This takes only a little
> 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 <
[hidden email]> 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
>
>
[hidden email]
>
>
> On Fri, Feb 5, 2021 at 7:12 AM Chuck Chandler <
[hidden email]>
> 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
>>
>>
[hidden email]
>>
>>
>> On Thu, Feb 4, 2021 at 6:54 PM Jack Brindle <
[hidden email]> 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 <
[hidden email]>
>>> 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 <
[hidden email]> 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 <
[hidden email]>
>>>> 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
>>>> >
>>>> >
[hidden email]
>>>> > ______________________________________________________________
>>>> > Elecraft mailing list
>>>> > Home:
http://mailman.qth.net/mailman/listinfo/elecraft>>>> > Help:
http://mailman.qth.net/mmfaq.htm>>>> > Post: mailto:
[hidden email]
>>>> >
>>>> > This list hosted by:
http://www.qsl.net>>>> > Please help support this email list:
http://www.qsl.net/donate.html>>>> > Message delivered to
[hidden email]
>>>>
>>>> --
>>> Sent from Gmail Mobile Chuck Chandler
[hidden email]
>>>
>>>
>>>
>