It depends on WHY there is dissipation. Is the filter out of alignment
(likely component failure/changing value) ? That sets up a mismatch to
the line from the exciter, and may also increase circulating currents in
the filter. That can result in too much of the fundamental being
dissipated, overheating the filter more. Failure might have been caused
by driving the amp on the wrong band.
When the driver (transceiver) is mismatched to its load, most solid
state output stages will throttle back to protect themselves. When this
happens, the transceiver produces less power.
73, Jim K9YC
On Fri,6/16/2017 9:57 AM, Jim Thomson wrote:
Date: Fri, 16 Jun 2017 12:44:43 +0100
From: Chris Wilson <chris@chriswilson.tv>
To: amps@contesting.com
Subject: Re: [Amps] Real time tests to see if an RF transformer is
saturating?
<Is heat produced in an LPF indicative of wasted energy to the antenna,
<or is it just the function of dissipating the unwanted harmonics and
<will be produced by any filter designed to remove them?
Chris.
### AFAIK, if the LPF heats up, its components are not sized correctly to
handle the
fundamental. The harmonics are reflected back towards the PA. The harmonics
are
not absorbed by the LPF, nor are they routed through to.... ground. But here
we are talking about
136 khz... so the cut off would have to be well below 272 khz, but higher
than 136 khz. Is that
even doable ? How much harmonic suppression is required ? How much
attenuation is
readily achievable, in a practical LPF circuit. I can well imagine a LPF
with a cut off of say
150 khz, having component values that are bizzare.
Jim VE7RF
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