[Elecraft] KPA-1500 Efficiency

[Jeff Blaine]

There's no way 40W drives exactly 1500W on all bands.  Here's what I get 
into a DL (no tuner).  Power measurements based on the LP100 which was 
calibrated by Larry last year - not what I would call a current cal but 
certainly better than a generic Bird.  Feed with a key-down in CW, with 
the data taken after about 5 seconds to get a stable reading.  Dont' 
take the values as gospel.  There is at least a 50w error range.

160        1644W

80            1466W

40            1515W

20            1436W

15        1371W

10        1414W

But it's definitely unrealistic to assume that the amp should have a 
uniform gain vs. frequency response.  The gain is going to be related to 
many things.

There is a LPF hanging off the back and it's insertion loss is a factor 
- and it's going to drift a touch as it heats up.  Theres the front  end 
which likly a pad.  The overall gain is be in compliance with the FCC 
regulation.  Most SS amps native gain is such that a few watts is enough 
to get LL output levels and I'm sure that's the case with the LDMOS even 
if they have a ton of NFB in the design.  Plus the effects of the 
combiners internally which are definitely not going to be completely 
flat.  And there is some compression that gets to be easily measurable 
once you hit about the KW level.  And temp.  And who knows what else.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 15-Aug-18 10:18 PM, Paul Baldock wrote:
> Are you saying it took exactly 40W input on each band to produce 1500W 
> out..
>
> I find the gain of the amp very different from band to band. For 
> example on 80M mine takes 32W to produce 1500W into a dummy load, and 
> 15M it takes 47W to produce 1500W in to a dummy load. That's a 
> variation of 1.7dB, not very flat.
>
> Also as others have reported as the amp warms up the gain decreases a 
> little (requires a bit more drive).
>
> - Paul KW7Y
>
> At 07:40 PM 8/15/2018, you wrote:
>> Just curious what other users of the KPA-1500 see as the efficiency 
>> reported by the KPA-1500 utility app.
>>
>> The following efficiencies are being report by my KPA-1500 utility 
>> app by band into a dummy load running 40 watts input and 1500 watts 
>> output:
>>
>> 80M CW:   61%
>> 80M SSB:  64%
>> 40M CW:   54%
>> 40M SSB:  59%
>> 20M CW:   52%
>> 20M SSB:  52%
>> 17M CW:   55%
>> 15M CW:   64%
>> 15M SSB:  62%
>> 12M CW:   68%
>> 10M CW:   56%
>> 10M SSB:  58%
>>
>> Does this compare favorably with other KPA-1500 owners?
>>
>> Charles  K5UA
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