[Elecraft] K3: incrementing Power level

[Ian White GM3SEK]

Joe Subich, W4TV wrote:
>
>Ian,
>
>> If this area of code is to be revisited, the gap in available power
>> settings on 50MHz also needs to be addressed.
>>
>> The maximum available power without the KPA3 is 8W on 50MHz, but the
>> minimum available power with the KPA3 activates is about 13W
>> - a jump of more than 60%.
>
>The "gap" is not a matter of code, it is a matter of the power
>available from the LPA on six meters.  The LPA can not make more
>than about 8 watts and stay "clean."  However, the gain (ca. 12 dB)
>of the HPA is such that 13W is a minimum practical output.  This
>leaves the gap.
>

Only the lower end of the gap, 8W, is a hardware limitation. The upper 
end of the gap, 13W, is set by DSP.

On 1.8-30MHz the KPA3 comes online above 12W. The excitation level is 
automatically reduced in DSP (by ca. 12dB, equal to the gain of the 
KPA3) so that the next notch of the PWR control will be a smooth 
transition from 12W to 13W. Then the excitation level is ramped up again 
to cover the 'high' power range from 13 to 100W.

The only thing wrong with 50MHz is that the 'high' power range appears 
to be using the same code as the lower bands. Nobody outside Elecraft 
knows how easy or difficult it would be to change the excitation levels 
for 50MHz to bring the next available step down to 9W... hence the 
respectful request to see if this problem can be addressed.


>If the external 50 MHz amplifier needs only 10 W for full output
>(e.g., a grid driven tetrode) additional grid swamping on an
>attenuator would be a wise investment.
>
That statement is only valid for some people's amplifiers and some 
countries' power limits. But regardless of all that, modifying the 
amplifier would be a clumsy external patch for a problem that resides 
strictly in the transceiver.

The real issue is that a gap of 60% in the available power level, from 
any transmitter, on any band, simply ain't elegant.



73 from Ian GM3SEK


>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Ian
>> White GM3SEK
>> Sent: Monday, December 07, 2009 1:39 PM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] K3: incrementing Power level
>>
>>
>> DOUGLAS ZWIEBEL wrote:
>> >Well, if this can be a user selection fine.  But I really like the
>> >"tiny steps" below 12 watts.  Please retain that.
>>
>> If this area of code is to be revisited, the gap in available power
>> settings on 50MHz also needs to be addressed.
>>
>> The maximum available power without the KPA3 is 8W on 50MHz, but the
>> minimum available power with the KPA3 activates is about 13W
>> - a jump of
>> more than 60%.
>>
>> This isn't important when the K3 is operating barefoot... but
>> with some
>> power amplifiers, in some countries, the legal power limit
>> falls right
>> into the hole.
>>
>>
>>
>> --
>>
>> 73 from Ian GM3SEK
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