I think you answered your own question !
While a Q of 10 would be on the low side for 2nd harmonic attenuation 12 to 15
puts you in a reasonable range. See W6SAI handbook if you have any questions
on this.
--- On Wed, 2/25/09, amps-request@contesting.com <amps-request@contesting.com>
wrote:
From: amps-request@contesting.com <amps-request@contesting.com>
Subject: Amps Digest, Vol 74, Issue 82
To: amps@contesting.com
Date: Wednesday, February 25, 2009, 11:00 AM
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Today's Topics:
1. Amp Building (Bob Maser)
----------------------------------------------------------------------
Message: 1
Date: Wed, 25 Feb 2009 03:38:27 -0000
From: "Bob Maser" <bmaser@tampabay.rr.com>
Subject: [Amps] Amp Building
To: "AMPS" <amps@contesting.com>
Message-ID: <43EA8A3A2B4941A8A08076401EACEE86@Main>
Content-Type: text/plain; format=flowed; charset="Windows-1252";
reply-type=original
As some of you are aware, I am building a tetrode amplifier mainly because I
have never tried it. All my efforts have always been with triodes. When I
first started collecting parts for this amp, I came across a really nice
B&W
852 tank coil. It was originally designed for use with a lower PLI and to
be used in Pi circuits. Indeed, the 852 seems to be tailor made for the
pair of 4CX1500B that I will be using. In looking at its usage in a Pi-L
tank circuit, I find that by juggling the Q for each band, it is
serviceable in a Pi-L configured tank circuit as well. I find that by using
a spreadsheet based tank circuit calculation program, I could take the
inductances that the 852 has for each of the bands(15M thru 75M) and
manipulate the Q so that it will be resonant. The resultant Q's ranged
from
12 up to 15. I used actual measured inductances rather than published data
using an AADE meter. I would appreciate hearing from the group whether Q
variations that I came up with will result in an amplifier that will have
good efficiency and at the same time, acceptable harmonic attenuation.
BTW, I ran the same analysis for a Pi tank circuit using the 852 and found
that with the exception of 20M, which needed a Q of 9.4 to resonate, the
other bands fell between 11.5 and 12.5 Q values.
Your comments will be appreciated.
Bob Maser W6TR
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