[Elecraft] Boost power supplies for RF amps

[David Orman]

I believe the new Anan-8000DLE does exactly this, and steps up the voltage
to 50V. No idea if there's any noise related to these boost converters.
Seems like a neat idea, just not sure how it will work in practice.

On Mon, Feb 20, 2017 at 4:08 PM, Bill Frantz <frantz at pwpconsult.com> wrote:

> The short answer is they can. It is only a matter of engineering time,
> cost, resulting price, number of customers and competing projects. In other
> words, the usual business considerations.
>
> Lets work the idea through for several of the Elecraft RF amplifiers:
>
> The 10-15W K3(s) amp: This amp can have significant IMD at low voltages as
> we have discovered with our QRP, all Elecraft, field day operation. The KX3
> seems to do better, so reengineering the amp may be a better solution. For
> field day, we try to have fresh batteries available.
>
> The 100W K3(s) internal amp: This amp also has low voltage IMD as we found
> during our 100W California QSO party expeditions. But, consider the K3(s)'s
> construction. The front of the radio is the digital portion, including the
> DSPs and the front panel computer. All of this digital noise is isolated
> from the analog circuits in the back of the radio. If Elecraft were to
> include a boost power supply with the internal amp, that high-current
> switcher would be in the analog section, and probably impossible to quiet.
> Solution: Get an external boost power supply.
>
> The KXPA100 external amp: This form factor would be an ideal place to
> include a boost power supply. The use profile includes portable battery
> operation and designing isolation for the power supply into the package
> seems straight forward.
>
> The KPA500 external amp: The amp setup procedure sets the voltage to to
> 65v to 85v and the specifications call for about 1000 VA of power or about
> 13A at 75v. That would be nearly 75A at 13.5 volts assuming 100%
> efficiency, so it would be a good idea to put the boost power supply next
> to the battery and run 75v to the amp. It would make a nice high power
> mobil rig.
>
> 73 Bill AE6JV
>
> In thread "Re: [Elecraft] Chinese ebay amps for KX3", on 2/20/17 at 5:47
> AM, pincon at erols.com (Charlie T, K3ICH) wrote:
>
> So now, tell me why a mid-sized radio can't have a built in 12 V to say, 50
>> V converter to drive some HV FETs for cleaner output specs like the Yuge
>> radios.
>>
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