Date: Tue, 22 Oct 2013 19:26:50 +0200
From: peter chadwick <g8on@fsmail.net>
To: Jim Thomson <jim.thom@telus.net>, amps@contesting.com
Subject: Re: [Amps] ?200-ohm tank and "un-un" in HF amp design
## I checked..and cant find any reference to minimum harmonic suppression
requirements anywhere......so far.
If you manage to find out..... pse let me know.
Jim VE7RF
Jim,
The regulations state in level in the feedline. However, I could ask one of my
friends at Industry Canada what they think.....
73
Peter G3RZP
========================================
Message Received: Oct 22 2013, 03:06 PM
From: "Jim Thomson" <jim.thom@telus.net>
To: amps@contesting.com
Cc:
Subject: [Amps] ?200-ohm tank and "un-un" in HF amp design
Date: Mon, 21 Oct 2013 10:32:27 +0200
From: peter chadwick <g8on@fsmail.net>
To: amps@contesting.com
Subject: Re: [Amps] ?200-ohm tank and "un-un" in HF amp design?
>The touted higher harmonic suppression of a PI-L is mainly a myth.....a plane
>jane PI is more than ample for harmonic suppression.<
As a Class AB stage has a second harmonic component of plate current only 6dB
down on the fundamental, what sort of Q do you run in the pi network to get the
extra 37dB of suppression needed to meet the FCC regulations or the extra 44dB
needed elsewhere?
73
Peter G3RZP
## ameritron uses a simple PI net on 40-10m on their bigger amps...and it
easily meets the 44 db down FCC requirements. Ameritron uses a PI-L on
160+80m..but that?s so a smaller load cap can be used.
My ants all exhibit sky high swr on their harmonics..including the 3rd...so
whats the problem ? Me, I could care less about harmonic suppression since
the amp kills most of it..and the ants kill the rest. My F12 40m yagi
barely resonates just a bit below the
12m band...and not at all on 15m. Optibeam uses linear decoupling stubs on
their 40m yagis so they wont resonate on 15m. I enter a Q of 8-10 on
the GM3SEK spreadsheet for all my hb amps. 30-36 db of 2nd harmonic
suppression
is plenty imo..... from any amp. With 1 kw out....and 36 db down.... that
means 1/4 watt on the 2nd harmonic. .25 watt into a sky high swr isnt
gonna bother anybody anytime soon.
Jim VE7RF
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