[Top] [All Lists]

Re: [Amps] Real time tests to see if an RF transformer is

Subject: Re: [Amps] Real time tests to see if an RF transformer is
From: Jim Brown <>
Date: Fri, 16 Jun 2017 12:11:02 -0700
List-post: <>
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 <>
Subject: Re: [Amps] Real time tests to see if an RF transformer is

<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?

###  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 
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.


Amps mailing list

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>