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Possible K3 over shoot on transmit

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Possible K3 over shoot on transmit

Just started noticing that occasionally the first character sent on CW will peg the watt meter on the KPA500. It does not fault. Sometimes a QSY to a different band or even a different band segment will trigger it again, sometimes not. Both of my antennas require my KAT500 which seems to have found acceptable matches for both antennas on the appropriate bands. It just uses a previous found solution when QSYing. Trying to determine which piece of equipment might have an issue. Planning on sending the K3 in for a check up but was hoping to have a K4 here first.
Any thoughts?
73, Gary KC9EE

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Re: Possible K3 over shoot on transmit

I’ve never seen this on my K3/PKA500/KAT500 setup.

Just went back into the check, and all is normal!

73 Tom W4KX

> On Jan 12, 2020, at 12:32 PM, Gary Hunt via Elecraft <[hidden email]> wrote:
>
> Just started noticing that occasionally the first character sent on CW will peg the watt meter on the KPA500. It does not fault. Sometimes a QSY to a different band or even a different band segment will trigger it again, sometimes not. Both of my antennas require my KAT500 which seems to have found acceptable matches for both antennas on the appropriate bands. It just uses a previous found solution when QSYing. Trying to determine which piece of equipment might have an issue. Planning on sending the K3 in for a check up but was hoping to have a K4 here first.
> Any thoughts?
> 73, Gary KC9EE
>
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Re: Possible K3 over shoot on transmit

I also just caused this anomaly by first slightly adjusting the K3 power output. First character again sent the KPA 500 to 700 watts. I'm going to see if I can find an accurate watt meter and see if I can see something on the K3 output.
KC9EE

Sent from Yahoo Mail on Android

On Sun, Jan 12, 2020 at 12:01 PM, Tom Doligalski<[hidden email]> wrote: I’ve never seen this on my K3/PKA500/KAT500 setup.

Just went back into the check, and all is normal!

73 Tom W4KX

Elecraft mailing list

Re: Possible K3 over shoot on transmit

In reply to this post by Elecraft mailing list

There are two things at play here. First, the KPA500 has an unregulated power supply. On first key down, the power will spike, then quickly lower as the big filter capacitors decay from their peak voltage to the rms voltage. This is normal and we all see it. While I am sure you are seeing this, I don’t think it is what you are commenting about.

The second thing is that over time the K3 power calibration may change. One of the symptoms of poor calibration is power spiking, and I suspect this is what you are seeing. The solution is easy, perform a power calibration on the K3. The best way is to use the K3 utility’s Calibration selection; follow its directions and you should see improved performance.

If that doesn’t correct the situation, let us know!

73!
Jack, W6FB

> On Jan 12, 2020, at 9:32 AM, Gary Hunt via Elecraft <[hidden email]> wrote:
>
> Just started noticing that occasionally the first character sent on CW will peg the watt meter on the KPA500. It does not fault. Sometimes a QSY to a different band or even a different band segment will trigger it again, sometimes not. Both of my antennas require my KAT500 which seems to have found acceptable matches for both antennas on the appropriate bands. It just uses a previous found solution when QSYing. Trying to determine which piece of equipment might have an issue. Planning on sending the K3 in for a check up but was hoping to have a K4 here first.
> Any thoughts?
> 73, Gary KC9EE
>
> ______________________________________________________________
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Bob McGraw - K4TAX

Re: Possible K3 over shoot on transmit

In reply to this post by Elecraft mailing list

Yep, the power control circuit does have a bit of initial character
overshoot.    This is noticed when changing power levels or when
changing bands and a few other instances which I don't recall.   Since
it occurs on the first CW element only, and doesn't fault the amp, I
don't consider it of concern.

You do have the ALC active from the amp and correctly set in the amp
menu and the K3S menu.......don't you?   That's what it is there for.
Just be sure during normal operation the amp ALC is not active as seen
on the K3S ALC indicator.

73

Bob, K4TAX

On 1/12/2020 11:32 AM, Gary Hunt via Elecraft wrote:

> Just started noticing that occasionally the first character sent on CW will peg the watt meter on the KPA500. It does not fault. Sometimes a QSY to a different band or even a different band segment will trigger it again, sometimes not. Both of my antennas require my KAT500 which seems to have found acceptable matches for both antennas on the appropriate bands. It just uses a previous found solution when QSYing. Trying to determine which piece of equipment might have an issue. Planning on sending the K3 in for a check up but was hoping to have a K4 here first.
> Any thoughts?
> 73, Gary KC9EE
>
> ______________________________________________________________
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Elecraft mailing list

Re: Possible K3 over shoot on transmit

Actually ALC is there because people expect it to be there. We recommend not using ALC between the KPA500 and K3.

73!
Jack, W6FB

> On Jan 12, 2020, at 12:00 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>
> Yep, the power control circuit does have a bit of initial character overshoot. This is noticed when changing power levels or when changing bands and a few other instances which I don't recall. Since it occurs on the first CW element only, and doesn't fault the amp, I don't consider it of concern.
>
> You do have the ALC active from the amp and correctly set in the amp menu and the K3S menu.......don't you? That's what it is there for. Just be sure during normal operation the amp ALC is not active as seen on the K3S ALC indicator.
>
> 73
>
> Bob, K4TAX
>
> On 1/12/2020 11:32 AM, Gary Hunt via Elecraft wrote:
>> Just started noticing that occasionally the first character sent on CW will peg the watt meter on the KPA500. It does not fault. Sometimes a QSY to a different band or even a different band segment will trigger it again, sometimes not. Both of my antennas require my KAT500 which seems to have found acceptable matches for both antennas on the appropriate bands. It just uses a previous found solution when QSYing. Trying to determine which piece of equipment might have an issue. Planning on sending the K3 in for a check up but was hoping to have a K4 here first.
>> Any thoughts?
>> 73, Gary KC9EE
>>
>> ______________________________________________________________
>> 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]
>
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Jim Brown-10

Re: Possible K3 over shoot on transmit

On 1/12/2020 1:08 PM, Jack Brindle via Elecraft wrote:
> Actually ALC is there because people expect it to be there. We recommend not using ALC between the KPA500 and K3.
>

Exactly that statement is in the User Manual for my 1979-vintage Ten Tec
Titan 425 legal limit amps. They were designed by K4XU, who also
designed the RF section (but not the control circuitry) of the Alpha 86
and 87A.

73, Jim K9YC
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Brian Hunt

Re: Possible K3 over shoot on transmit

In reply to this post by Bob McGraw - K4TAX

I saw this problem with my K3 #4xxx and discovered a large voltage drop between the PS and K3 using the provided power cable. Cured the problem by: 1) shorter & fatter power cable, 2) increased the PS (Astron 30A linear) to 14.5v, and 3) running the K3 utility power calibration _twice_ back-to-back. Why it took 2x I don't know but it's been 100% fine ever since.

73,
Brian, K0DTJ
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Bob McGraw - K4TAX

Re: Possible K3 over shoot on transmit

Since the K3/K3S has the ability to indicate voltage on the display, from actual experience, between RX and TX there should be less than 0.5 volts difference in CW mode, key closed at 100 watts output. Anything greater indicates poor power supply regulation, or more likely, excessive resistance in the DC power cables or related connections.

NEVER use a power distribution strip but always connect the radio directly to the power supply terminals. And without added in- line fuses unless a battery is used for the DC source as a battery does not contain current limiting as found with a power supply.

Bob, K4TAX

Sent from my iPhone

> On Jan 12, 2020, at 6:01 PM, Brian Hunt <[hidden email]> wrote:
>
> I saw this problem with my K3 #4xxx and discovered a large voltage drop between the PS and K3 using the provided power cable. Cured the problem by: 1) shorter & fatter power cable, 2) increased the PS (Astron 30A linear) to 14.5v, and 3) running the K3 utility power calibration _twice_ back-to-back. Why it took 2x I don't know but it's been 100% fine ever since.
>
> 73,
> Brian, K0DTJ
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>