KPA1500 in CQWW CW

[K9MA]

This was my first serious contest effort with the new amplifier. It is
paired with a K3. It survived about 24 hours of operation, though it
faulted a few times, as described below. Clearly, the protection
circuitry did its job. Firmware is 1.87.

A couple glitches:

The power gain drifts downward as the transistors heat up. If I start
out at 1500 W, it will drift down to about 1100, without changing
frequency or SWR. Conversely, if I turn the drive up after the amp is
warm, and forget to turn it back down, the amp will fault when cold.
Since the amp is talking to the K3, couldn't some clever software fix this?

Despite setting tune power to 40 W, the ATU sometimes just won't get the
SWR below 1.4:1 or so. This is with antennas below 2:1, and the ATU stop
set to 1.0. This happens on 40 meters, so it's probably not an ATU L/C
resolution limit. This 1.4:1 SWR is sometimes high enough to limit
output to well below 1500 W due to high drive power or high current. I
have not yet tried manually tuning the ATU to see if I can get the SWR
lower.

Finally, after "training" the ATU across the band, I sometimes find that
the SWR has gone up significantly at some frequencies. I don't believe
this is due to changing antenna SWR. It seems more like the ATU has
"forgotten" the settings, or tried to retune itself without permission.
(HiSWR RETUNE OFF)

Has anyone else seen similar issues?

73,

Scott K9MA

--
Scott  K9MA

[hidden email]

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[Richard Zalewski]

Yes to all...

Richard
*W7ZR* ex:5C5Z, CN2ZR, K2JSP, W6SBZ, W7KXR, K9ZIJ, W9KNF, W0KDF, W0MQU,
J68ZR, KC6ZR, PJ4/W7ZR, KH2,W7ZR, KH6/W7ZR, V31ZR, VK4AAZ, XE2DV


*Be joyful in hope, patient in affliction, faithful in prayer*


On Mon, Nov 26, 2018 at 5:15 PM K9MA <[hidden email]> wrote:

> This was my first serious contest effort with the new amplifier. It is
> paired with a K3. It survived about 24 hours of operation, though it
> faulted a few times, as described below. Clearly, the protection
> circuitry did its job. Firmware is 1.87.
>
> A couple glitches:
>
> The power gain drifts downward as the transistors heat up. If I start
> out at 1500 W, it will drift down to about 1100, without changing
> frequency or SWR. Conversely, if I turn the drive up after the amp is
> warm, and forget to turn it back down, the amp will fault when cold.
> Since the amp is talking to the K3, couldn't some clever software fix this?
>
> Despite setting tune power to 40 W, the ATU sometimes just won't get the
> SWR below 1.4:1 or so. This is with antennas below 2:1, and the ATU stop
> set to 1.0. This happens on 40 meters, so it's probably not an ATU L/C
> resolution limit. This 1.4:1 SWR is sometimes high enough to limit
> output to well below 1500 W due to high drive power or high current. I
> have not yet tried manually tuning the ATU to see if I can get the SWR
> lower.
>
> Finally, after "training" the ATU across the band, I sometimes find that
> the SWR has gone up significantly at some frequencies. I don't believe
> this is due to changing antenna SWR. It seems more like the ATU has
> "forgotten" the settings, or tried to retune itself without permission.
> (HiSWR RETUNE OFF)
>
> Has anyone else seen similar issues?
>
> 73,
>
> Scott K9MA
>
> --
> Scott  K9MA
>
> [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]
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]