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Re: [Amps] HV MOSFETs for RF

To: <amps@contesting.com>, <jtml@vla.com>
Subject: Re: [Amps] HV MOSFETs for RF
From: Catherine James <catherine.james@att.net>
Reply-to: Catherine James <catherine.james@att.net>
Date: Fri, 5 May 2017 17:51:16 +0000 (UTC)
List-post: <amps@contesting.com">mailto:amps@contesting.com>
This is one reason hams are always challenged in the amplifier area.  The 
commercial
users are heavily focused on FM, with its 100% duty cycle but lack of any 
requirement for linearity.

The modes hams use tend to either be 100% duty cycle and nonlinear, but work 
well at low power
(FM, PSK31, JT modes), or benefit strong from high power and have a lower duty 
cycle, but have
a requirement that they be linear (SSB).

So the people who most want and need ham amps are SSB users, and they have 
little
interest in anything that is nonlinear.  If a component works well at high 
power in nonlinear
operation but has to be significantly de-rated to get acceptable IMD, it's 
unlikely to be a
good fit for ham SSB usage.  Advances in the radio art that are highly 
efficient but fundamentally
nonlinear are of little benefit to most hams.

Does anyone outside of ham radio care about modulation modes that require 
excellent linearity?

73,
Cathy
N5WVR


John Lyles <jtml@losalamos.com> wrote:

> Up to now, most of the innovation posted on line has been using nonlinear 
> classes 
> like E for homebrew AM transmitters (another topic!) and the hams there 
> have made great strides with kW level designs.

> But building linear (or Kahn EER/Linc) amplifiers and getting around the laws 
> of physics (very 
> low Z due to low voltages) with the newer devices is the way to look forward. 
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