[Amps] how to measure tank

[DAVE WHITE]

I'd echo W6TC's good advice - a resistor of the same value as your calculated resonant load impedance or that off the data sheet for the drive and ht you're using.  Just make sure it's a non-inductive resistor, of course.  And if you're running any cathode bias then make sure that the cathode is at rf ground.
 
If I were you I'd try to do the measurements with the same capacitors at calculated settings (an LCR meter was one of the best investments I ever made), the same switch, the same plate blocking cap and the same plate choke in the same formation as you'll use in the amp.  even better, actually assemble those bits in the plate tank and put the lid on to do your mesurements as it all measures differently on the bench!  
I learned that the hard way having silver soldered and silver plated a tank coil that I'd resonated outside the amp with a dip meter, only to find that the resonant positions had changed wildly.  Much rework, snarling and and swearing ensued.....
 
Oh, and check the series and parallel resonances in your plate choke or things will go spectacularly "POP"......
 
Are you using a PI or a PI-L?  If the latter, you can set up the L section to your desired image impedance in much the same way, just setting up the matching one bit at a time.  Choose the right image impedance and you'll get optimal harmonic suppression.  WB6BLD wrote a little program called PIEL which you can download, but I can't seem to find the link.  I'm sure a littke Googling will find it.  This may help?
 
I'm, sure you knew all this anyway, in which case please discount this email as the rantings of a crazed Englishman who's suffered too much RF damage..... 
 
cheers
 
Dave G0OIL / K2MOO

--- On Sun, 30/11/08, George Badger <gbadger at sbcglobal.net> wrote:

From: George Badger <gbadger at sbcglobal.net>
Subject: Re: [Amps] how to measure tank
To: "Lynn Osterbur" <no9z at yahoo.com>, amps at contesting.com
Date: Sunday, 30 November, 2008, 5:02 AM

Lynn
Put a resistor from plate ground to simulate the load and look into the output
with an MFJ 259. Tune for a match. Works like a charm.
George    W6TC


----- Original Message ----
From: Lynn Osterbur <no9z at yahoo.com>
To: amps at contesting.com
Sent: Saturday, November 29, 2008 6:50:47 PM
Subject: [Amps] how to measure tank

I am starting to forget all I know!

Components  Homebrew amp and cushman service monitor

What is the proper way to measure a pi network with a tracking generator and
spectrum analyzer.
I am mostly interested in the connections to the tank circuit.

using cushman 5100 with tracking generator and spectrum analyzer.  I havent
used it for 
3 or 4 years and that was on a set of 2m bandpass filters.  I also assume that
I will need to
put a load resistor across the tube equal to the load resistance.

Lynn NO9Z


      
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