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KPA1500 Drive Power

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john@kk9a.com

KPA1500 Drive Power

My KPA500 also has slightly inconsistent output. If I recall output drops
a little after the first few seconds of key down. Perhaps it is normal for
solid state amps as I have never noticed this with a tube amp. This may be
more of a concern with a legal limit amp if you want to keep it as close
to 1500 watts without going over.

John KK9A

Bill Stravinsky k3wjv wrote:

Yup, as the temp climbs the output drops some. Even though I'm glad I
got the solid state amp I still prefer tubes, hi. The drop is anywhere
between 100 to maybe 300 watts.I never really noted the exact numbers.
BillK3WJV
p.s. I'm thinking its a normal solid state thing.

On Wednesday, May 30, 2018, 4:23:47 PM EDT, K9MA <k9ma at
sdellington.us> wrote:

I'm using the K3 with the Elecraft interface cable. I've noticed the
the CW drive power required by mine varies considerably, both with
temperature and SWR. If I set the K3 output for a KPA1500 output of
1500 W output initially, the output will drop to perhaps 1100 W when the
temperature stabilizes at around 65 C. (I've ruled out any change in
antenna impedance, etc.) A similar change occurs if the SWR goes from
1:1 to 1.2:1 when changing frequency or switching antennas. I haven't
changed the ALC from the default setting. Has anyone else noticed this?

73,

Scott K9MA

--
Scott K9MA

k9ma at sdellington.us

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Rick Tavan-2

Re: KPA1500 Drive Power

I've seen some gain drift with temperature, too. I've wondered if there
might be a way to feed back drive power change requests to a K3, or other
radio with adequate command capabilities, to maintain a target output power
(say, 1500w) as the amp warms and cools. This should be done slowly - on
the order of seconds, not milliseconds like ALC. KPA1500 Utility knows its
output power and could be programmed to generate the requests. I don't know
how to get commands into a K3 that has its serial port connected to a
logging program. There are some port-sharing tools out there that might
work, but I'm not familiar with them. In any case, it would require some
engineering at Elecraft. In the meantime, I keep an eye on output and tweak
the drive manually to stay both powerful and legal.

/Rick N6XI

Rick Tavan
Truckee, CA

On Thu, May 31, 2018 at 10:01 AM, [hidden email] <[hidden email]> wrote:

> My KPA500 also has slightly inconsistent output. If I recall output drops
> a little after the first few seconds of key down. Perhaps it is normal for
> solid state amps as I have never noticed this with a tube amp. This may be
> more of a concern with a legal limit amp if you want to keep it as close
> to 1500 watts without going over.
>
> John KK9A
>
> Bill Stravinsky k3wjv wrote:
>
> Yup, as the temp climbs the output drops some. Even though I'm glad I
> got the solid state amp I still prefer tubes, hi. The drop is anywhere
> between 100 to maybe 300 watts.I never really noted the exact numbers.
> BillK3WJV
> p.s. I'm thinking its a normal solid state thing.
>
> On Wednesday, May 30, 2018, 4:23:47 PM EDT, K9MA <k9ma at
> sdellington.us> wrote:
>
> I'm using the K3 with the Elecraft interface cable. I've noticed the
> the CW drive power required by mine varies considerably, both with
> temperature and SWR. If I set the K3 output for a KPA1500 output of
> 1500 W output initially, the output will drop to perhaps 1100 W when the
> temperature stabilizes at around 65 C. (I've ruled out any change in
> antenna impedance, etc.) A similar change occurs if the SWR goes from
> 1:1 to 1.2:1 when changing frequency or switching antennas. I haven't
> changed the ALC from the default setting. Has anyone else noticed this?
>
> 73,
>
> Scott K9MA
>
> --
> Scott K9MA
>
> k9ma at sdellington.us
>
> ______________________________________________________________
> 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]
>

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K9MA

Re: KPA1500 Drive Power

I agree with Rick: A way to slowly adjust the drive power automatically to maintain constant peak output would solve the problem. I'd think the KPA1500 firmware could do this with the K3 via the accessory cable. Probably the K3 should revert to its original output when the KPA1500 is cold, or power would initially overshoot. Better yet if the amp could remember drive power for each band as a function of temperature.

While it's annoying to have to keep fiddling with the power control, I can understand that there are higher priorities now.

73,
Scott K9MA

----------

Scott Ellington

--- via iPad

> On May 31, 2018, at 1:06 PM, Rick Tavan <[hidden email]> wrote:
>
> I've seen some gain drift with temperature, too. I've wondered if there
> might be a way to feed back drive power change requests to a K3, or other
> radio with adequate command capabilities, to maintain a target output power
> (say, 1500w) as the amp warms and cools. This should be done slowly - on
> the order of seconds, not milliseconds like ALC. KPA1500 Utility knows its
> output power and could be programmed to generate the requests. I don't know
> how to get commands into a K3 that has its serial port connected to a
> logging program. There are some port-sharing tools out there that might
> work, but I'm not familiar with them. In any case, it would require some
> engineering at Elecraft. In the meantime, I keep an eye on output and tweak
> the drive manually to stay both powerful and legal.
>
> /Rick N6XI
>
>
> Rick Tavan
> Truckee, CA
>
>> On Thu, May 31, 2018 at 10:01 AM, [hidden email] <[hidden email]> wrote:
>>
>> My KPA500 also has slightly inconsistent output. If I recall output drops
>> a little after the first few seconds of key down. Perhaps it is normal for
>> solid state amps as I have never noticed this with a tube amp. This may be
>> more of a concern with a legal limit amp if you want to keep it as close
>> to 1500 watts without going over.
>>
>> John KK9A
>>
>> Bill Stravinsky k3wjv wrote:
>>
>> Yup, as the temp climbs the output drops some. Even though I'm glad I
>> got the solid state amp I still prefer tubes, hi. The drop is anywhere
>> between 100 to maybe 300 watts.I never really noted the exact numbers.
>> BillK3WJV
>> p.s. I'm thinking its a normal solid state thing.
>>
>> On Wednesday, May 30, 2018, 4:23:47 PM EDT, K9MA <k9ma at
>> sdellington.us> wrote:
>>
>> I'm using the K3 with the Elecraft interface cable. I've noticed the
>> the CW drive power required by mine varies considerably, both with
>> temperature and SWR. If I set the K3 output for a KPA1500 output of
>> 1500 W output initially, the output will drop to perhaps 1100 W when the
>> temperature stabilizes at around 65 C. (I've ruled out any change in
>> antenna impedance, etc.) A similar change occurs if the SWR goes from
>> 1:1 to 1.2:1 when changing frequency or switching antennas. I haven't
>> changed the ALC from the default setting. Has anyone else noticed this?
>>
>> 73,
>>
>> Scott K9MA
>>
>> --
>> Scott K9MA
>>
>> k9ma at sdellington.us
>>
>> ______________________________________________________________
>> 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]
>
> 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]

Michael Blake

Re: KPA1500 Drive Power

Are you sure that it is not the K3(s) itself that has unstable output power. I see this occur on my KPA500 and it is not getting hot.

Michael Blake
[hidden email] <mailto:[hidden email]>

> On May 31, 2018, at 4:09 PM, K9MA <[hidden email]> wrote:
>
> I agree with Rick: A way to slowly adjust the drive power automatically to maintain constant peak output would solve the problem. I'd think the KPA1500 firmware could do this with the K3 via the accessory cable. Probably the K3 should revert to its original output when the KPA1500 is cold, or power would initially overshoot. Better yet if the amp could remember drive power for each band as a function of temperature.
>
> While it's annoying to have to keep fiddling with the power control, I can understand that there are higher priorities now.
>
> 73,
> Scott K9MA
>
>
>
> ----------
>
> Scott Ellington
>
> --- via iPad
>
>> On May 31, 2018, at 1:06 PM, Rick Tavan <[hidden email]> wrote:
>>
>> I've seen some gain drift with temperature, too. I've wondered if there
>> might be a way to feed back drive power change requests to a K3, or other
>> radio with adequate command capabilities, to maintain a target output power
>> (say, 1500w) as the amp warms and cools. This should be done slowly - on
>> the order of seconds, not milliseconds like ALC. KPA1500 Utility knows its
>> output power and could be programmed to generate the requests. I don't know
>> how to get commands into a K3 that has its serial port connected to a
>> logging program. There are some port-sharing tools out there that might
>> work, but I'm not familiar with them. In any case, it would require some
>> engineering at Elecraft. In the meantime, I keep an eye on output and tweak
>> the drive manually to stay both powerful and legal.
>>
>> /Rick N6XI
>>
>>
>> Rick Tavan
>> Truckee, CA
>>
>>> On Thu, May 31, 2018 at 10:01 AM, [hidden email] <[hidden email]> wrote:
>>>
>>> My KPA500 also has slightly inconsistent output. If I recall output drops
>>> a little after the first few seconds of key down. Perhaps it is normal for
>>> solid state amps as I have never noticed this with a tube amp. This may be
>>> more of a concern with a legal limit amp if you want to keep it as close
>>> to 1500 watts without going over.
>>>
>>> John KK9A
>>>
>>> Bill Stravinsky k3wjv wrote:
>>>
>>> Yup, as the temp climbs the output drops some. Even though I'm glad I
>>> got the solid state amp I still prefer tubes, hi. The drop is anywhere
>>> between 100 to maybe 300 watts.I never really noted the exact numbers.
>>> BillK3WJV
>>> p.s. I'm thinking its a normal solid state thing.
>>>
>>> On Wednesday, May 30, 2018, 4:23:47 PM EDT, K9MA <k9ma at
>>> sdellington.us> wrote:
>>>
>>> I'm using the K3 with the Elecraft interface cable. I've noticed the
>>> the CW drive power required by mine varies considerably, both with
>>> temperature and SWR. If I set the K3 output for a KPA1500 output of
>>> 1500 W output initially, the output will drop to perhaps 1100 W when the
>>> temperature stabilizes at around 65 C. (I've ruled out any change in
>>> antenna impedance, etc.) A similar change occurs if the SWR goes from
>>> 1:1 to 1.2:1 when changing frequency or switching antennas. I haven't
>>> changed the ALC from the default setting. Has anyone else noticed this?
>>>
>>> 73,
>>>
>>> Scott K9MA
>>>
>>> --
>>> Scott K9MA
>>>
>>> k9ma at sdellington.us
>>>
>>> ______________________________________________________________
>>> 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]
>>
>> 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
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>
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K9MA

Re: KPA1500 Drive Power

Absolutely. I have never seen such fluctuations of either output or grid current with my other amplifiers.

Scott K9MA

----------

Scott Ellington

--- via iPad

> On May 31, 2018, at 3:14 PM, Michael Blake <[hidden email]> wrote:
>
> Are you sure that it is not the K3(s) itself that has unstable output power.

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Jim Brown-10

Re: KPA1500 Drive Power

In reply to this post by Michael Blake

On 5/31/2018 1:14 PM, Michael Blake wrote:
> Are you sure that it is not the K3(s) itself that has unstable output power. I see this occur on my KPA500 and it is not getting hot.

Me too.

Jim K9YC
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