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KPA500 efficiency

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Yngvi (TF3Y)

KPA500 efficiency

Hi folks.

I'm wondering about the efficiency of the KPA500.
Mine, which I assembled a few days ago seems to exchibit 76-78% efficiency
on CW. Admittedly I havent tested it on SSB.

The HV stands at 57.6V under load with current at 14A. Hence 806W input.
Measured output using my LP-100A at 630W. Drive for this 29W on 12m.

What class is the amplifier operating in on CW? Does the class depend on
mode? I'm using the KPAK3AUX cable.

The operating temperature seems to remain close to 50C.

73, Yngvi TF3Y
http://www.tf3y.net
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Ignacy

Re: KPA500 efficiency

78% efficiency seems high. But your calculations assume that all the meters are accurate.

KPA500 is rated at 500W in linear mode and is supposed to have an efficiency around 50% at this level. At a higher drive the amp will be less linear but at a higher efficiency. At low power the efficiency increases linearly with output power. If about 50% with 500W then about 62% with 620W.

A data sheet for Microsemi 1 KW module shows efficiency curves in Fig 19 at www.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP61K25H.pdf‎. About 65% efficiency at 700W with IMD3<-40db. Reaching 80% at 1.4 KW and IMD3>-28db. The dissipation is about 370W at 700W level and 350 at the 1.4 KW level. These numbers do not include losses in transformers and filters.

Ignacy, NO9E

Yngvi (TF3Y)

Re: KPA500 efficiency

In reply to this post by Yngvi (TF3Y)

Hi Ignacy.

Many thanks for the response.

The reason for my query was that I was puzzled by my calculated efficiency
numbers - I felt they were high. This also led me to wonder about the
operating class of the amplifier, i.e. whether it was operating in linear
mode on CW or not.

I have confirmed the accuracy of the LP-100A which conforms broadly with
the built in meter of the KPA500.
The LP-100A was factory built so I'd get a NIST calibrated unit. It's an
impressive instrument.

I have not confirmed the accuracy of the KPA500 voltage and current
measurements. I don't think there is anything to adjust in order to
calibrate these.

I did get a response from Wayne N6KR on another email list, where I posted
my message as well. I'm sure he doesn't mind me quoting him: "As with all
broadband power amplifiers, the efficiency of the KPA500 varies somewhat
from band to band due to variations in matching circuit efficiency and
transformer
performance. That's why "typical" efficiency is specified."
However, I got no comment on the operating class of the amplifier on CW or
whether it depends on what mode you are operating the K3. Anyone?

73, Yngvi TF3Y
http://www.tf3y.net

On Tue, Jul 23, 2013 at 6:45 PM, Ignacy <[hidden email]> wrote:

> 78% efficiency seems high. But your calculations assume that all the meters
> are accurate.
>
> KPA500 is rated at 500W in linear mode and is supposed to have an
> efficiency
> around 50% at this level. At a higher drive the amp will be less linear but
> at a higher efficiency. At low power the efficiency increases linearly
> with output power. If about 50% with 500W then about 62% with 620W.
>
> A data sheet for Microsemi 1 KW module shows efficiency curves in Fig 19 at
> www.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP61K25H.pdf. About 65%
>
> efficiency at 700W with IMD3<-40db. Reaching 80% at 1.4 KW and IMD3>-28db.
> The dissipation is about 370W at 700W level and 350 at the 1.4 KW level.
> These numbers do not include losses in transformers and filters.
>
> Ignacy, NO9E
>
>
>
>
>
> --
> View this message in context:
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> Sent from the Elecraft mailing list archive at Nabble.com.
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Lyle Johnson

Re: KPA500 efficiency

The KPA500 has no knowledge of mode. It is a "linear" amplifier, only
and always.

73,

Lyle KK7P

> However, I got no comment on the operating class of the amplifier on CW or
> whether it depends on what mode you are operating the K3. Anyone?

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Yngvi (TF3Y)

Re: KPA500 efficiency

Thanks for the info Lyle. Interesting!

I must study the KPA500 design.
I find it a bit embarrassing having assembled the KPA500 without having
more fundamental insight into its design.

73, Yngvi TF3Y

On Tue, Jul 23, 2013 at 9:26 PM, Lyle Johnson <[hidden email]> wrote:

> The KPA500 has no knowledge of mode. It is a "linear" amplifier, only and
> always.
>
> 73,
>
> Lyle KK7P
>
>
> However, I got no comment on the operating class of the amplifier on CW or
>> whether it depends on what mode you are operating the K3. Anyone?
>>
>
>