[Elecraft] L31 change

[Don Brown]

Hi

Thanks for the explanation.=20

Don Brown



  ----- Original Message -----=20
  From: John, KI6WX<mailto:ki6wx@pacbell.net>=20
  To: Elecraft<mailto:elecraft@mailman.qth.net>=20
  Sent: Sunday, March 07, 2004 2:53 PM
  Subject: Re: [Elecraft] L31 change


  I am the person responsible for the design change of L31 from 10uH to =
12uH.
  When I designed the temperature compensation circuit, I needed to get =
a
  wider swing out of the PLL reference oscillator to make up for the =
reduced
  voltage swing at the varactor diodes.  The easiest way to do this was =
to
  increase the value of L31 which will pull the 12 MHz crystal about 20% =
more.
  This worked fine with the crystals that ECS was shipping in early =
2003.

  Over time, the motional inductance of the ECS crystals has dropped.  =
In the
  beginning of 2003 it was about 6.7mH, but toward the end of 2003 it is =
now
  less than 6mH.  This increases the frequency swing of the PLL =
reference
  oscillator, which should normally be in the range of 11 to 15 kHz.  As =
the
  frequency range increases, it decreases the effectiveness of the =
temperature
  compensation circuit.  This can be compensated either by changing the
  resistor values in the temperature compensation circuit or reducing =
the
  value of L31.

  It is a lot easier to reduce the value of L31, so this is the approach =
that
  has been adopted.  If a K2 shows a PLL reference frequency range =
greater
  than 15 kHz, Elecraft will send a 10uH inductor to get it back within =
the
  normal range.  This is done to better match the temperature =
compensation
  circuit; changing the inductor has no other effect on the K2's =
performance.

  -John
   KI6WX

  ----- Original Message -----=20
  From: "Don Brown" <DolfinDon@msn.com<mailto:DolfinDon@msn.com>


  Hi

  The newest manual still has it at 12 uH. I just bought the newest =
version of
  the manual as well as I downloaded it. The errata sheet was included =
with
  the manual with the note to change it to 10 uH. I am building a K2 now =
and I
  had already installed a 12 uH, but it seems to work to spec that way. =
I was
  just wondering if I should replace it with the 10 uH and re-run CAL =
PLL. I
  have not heard any information on why it was changed back and if it =
improves
  anything.

  Don


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