On 2019-11-04 7:34 PM, W2xj wrote:
One could always have a modular approach which is how other
industries approach this.
Sure, a modular approach would work well ... a 12V/60W PA or
a 40V/200W PA that would plug into the same space. Not exactly
rocket science.
> BTW, predistortion is common practice is a number of industries.
Yes, I'm very familiar with predistortion - it was common in analog
UHF TV transmitters 30+ years ago and integral to broadcast HDTV
today. Still, proper setup was not something for an "appliance
operator" and tracking changing operating conditions (e.g., fading
batteries) takes a lot of computational horsepower. On top of that,
predistortion works best when the amplifier chain is not pushed for
every last fraction of a watt of output - best results will always
be obtained when the PA chain is reasonably clean to start with.
73,
... Joe, W4TV
On 2019-11-04 7:34 PM, W2xj wrote:
One could always have a modular approach which is how other industries approach
this. Broadband combiners are not that complicated. BTW, predistortion is
common practice is a number of industries.
Sent from my iPad
On Nov 4, 2019, at 5:03 PM, Joe Subich, W4TV <li...@subich.com> wrote:
On 2019-11-04 4:44 PM, Scott Manthe wrote:
Elecraft's design philosophy dictates that their radio be capable of
portable/field operation, so that's how they design their radios.
They're lightweight, efficient, and operate off 12 volts.
If that's the design philosophy, limit the power output to 60 W PEP.
Elecraft already have *two* other 12V capable radios - the KX2 and KX3 -
of one doesn't count the K2. *WHY* create another dirty 12V radio
("active predistortion" is not the solution) when one can have a clean
60W radio at 12V or a clean 200W radio at 40V?
Build a DC-DC supply for the 40V PA stage if one wants to run it from
an automobile electrical system (or install a separate 48V alternator,
regulator and battery specifically for the PA stage).
Increasing transmit IMD by a factor of 40 just to operate the radio
at 100 W PEP on a 12 battery is unconscionable given today's state
of the art. It was different when 48V transistors/FETs were not
available but that ship sailed almost 20 years ago.
73,
... Joe, W4TV
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