[Amps] Amps Digest, Vol 74, Issue 82

[Ronald Brown]

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 at contesting.com <amps-request at contesting.com> wrote:
From: amps-request at contesting.com <amps-request at contesting.com>
Subject: Amps Digest, Vol 74, Issue 82
To: amps at 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 at tampabay.rr.com>
Subject: [Amps] Amp Building
To: "AMPS" <amps at contesting.com>
Message-ID: <43EA8A3A2B4941A8A08076401EACEE86 at 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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End of Amps Digest, Vol 74, Issue 82
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