[Test-Equipment] Xtal Tester

[Fuqua, Bill L]

  You know, many of us have a way to test the activity with out making an oscillator.
If the crystal is labled you can put it in series with your synthesized signal generator and 
sweep it. If you provide a 50 ohm resistor at the on one end and drive it with a 50 ohm source 
when you get the peak you can look at the ratio of the voltage driven side of the crystal and compare it
to that across the 50 ohm resistor going to ground and calculate its series resistance. A simple
voltage divider since the series reactances have cancled out. There will be a slight error due to
current passing around the crystal due to holder capacitance but that should be minimal at low
frequencies. 
  If the series resistance is low it should be "active" high or you can't get a resonance it is dead.

73
Bill wa4lav

________________________________________
From: test-equipment-bounces at mailman.qth.net [test-equipment-bounces at mailman.qth.net] on behalf of Dino Papas [kl0s at cox.net]
Sent: Monday, March 18, 2013 1:47 PM
To: Discussion of Electronic Test Equipment
Subject: Re: [Test-Equipment] Xtal Tester

Joe - if you want a more capable tester you might consider W1FB's circuit in the January 1990 issue of QST and updated in the W1FB Design Notebook.  The PCB is available from FAR Circuits; makes a nice unit but you will need a signal generator and a counter in order to determine the xtal parameters (series resonant frequency, 3-dB response points and series resistance).

73 - Dino KL0S

On Mar182013, at 1325 PM, Precision Carburetor DP wrote:

> Hi Joe.
>
> In the July 1964 issue of CQ magazine page 30  there is an construction
> article for a crystal tester.  Below is a quote from a blurb on the title
> page.
>
>
>
> "The simple device described below was built to determine the condition of
> the many crystals around the shack."
>
>
>
> W6BLZ EH Marriner was the author.
>
> The simple circuit uses a 6AH6 pentode with a ma meter in the control grid
> circuit.  If there is some interest I will scan the article for anyone who
> wants it.
>
> Jerry
>
> W2JI

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