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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