[Elecraft] crystal oven question

[Don Brown]

Hi

I am building 2 XV144 transverters and I have the oven option for them and well as one to add to my XV50. I measured the current draw and until it comes up to temperature it draws about 300 ma after about 30 seconds the draw is down to about 70 ma cycling up to 150 ma. This is measuring it connected to a power supply while not installed. The mass of the crystal can will require a little more heat to bring it up to temperature so the heat time may be a little longer. With the oven installed there will be less air circulation and more mass so the current draw should be more stable at around 100 ma. Of course you would need to add this to the receive current of 250 ma so after a few minutes the current should be around 350 ma.  Measuring the current draw I read 380 ma after a suitable warm up time.

If you are using the K60XV you would be set up for 0-1 mw so the K2 final is turned off. The ALC circuit in the K2/K60<>XV will provide a 0-1 mw level for the transverter so the battery voltage should not matter that much. The transverter will draw about 5 amps at 20 watts out and about 3 amps at 5 watts out. There is not really a good way to bring out the internal battery power to supply the transverter without mounting another connector on the K2 rear panel. It may be better to run the K2 and the transverter on an external battery a little larger than the 2.9 amp hour battery in the K2 because of the increased demands of the transverter.

Don Brown
KD5NDB
  ----- Original Message ----- 
  From: Darrell Bellerive<mailto:ve7cla at shaw.ca> 
  To: Elecraft Email List<mailto:elecraft at mailman.qth.net> 
  Sent: Tuesday, June 01, 2004 2:46 PM
  Subject: Re: [Elecraft] crystal oven question


  Interesting discussion! I have been saving up my pennies for a 6 metre
  transverter and would like to run it off the K2 internal battery for
  portable operation.

  I was wondering if I should get the crystal oven or not.

  Searching the manual does not give much detail about current draw. The
  specs show receive current at about 250 mA which is about the same as my
  K2. I'm not sure if this is with or without the oven.

  If the transverter is optioned to only turn on the local oscillator when
  the transverter is in use, (JP9 1-2) what is the typical drift during
  warm up?

  How much current is used to power the oven, and to keep the local
  oscillator on?

  Is it possible and practical to wire JP9 to a rear mounted switch to
  manually switch the local oscillator off (JP9 1-2) for portable
  operation on HF, but continuously on (JP9 4-5) when on a power supply?
  In effect, sacrificing stability for current draw when portable.

  What is the power output from the 50 Mhz transverter when driving with
  the K60XV, and powering from the K2 internal battery at 3 amps maximum
  current draw?

  73,
  Darrell   VE7CLA   K2 #1973

  On Tue, 2004-06-01 at 12:10, AI4CQ ,James wrote:
  > A crystal oven consists of a heater in an enclosure for the crystal
  > and a temperature controller.  To be able to control the temperature
  > with heat a temperature must be chosen which is above the highest
  > normal operating temperature which is often more than 100 degrees F.  
  > 
  > A crystal will drift with temperature but for common cuts of crystal
  > not in a linear fashion.  The AT cut which is most common at HF drifts
  > in a S shaped plot when plotted temperature vs frequency with the
  > center of the S near room temperature. Crystals for ovens used in
  > frequency counters are often specially cut so they are most stable at
  > the temperature of the oven.   The frequency stability of a crystal in
  > a crystal oven is determined partly by the drift characteristics of
  > the crystal but mostly by the accuracy of the temperature control.  
  > 
  > The disadvantage of a crystal oven is it requires power to generate
  > the heat and it is not suited for portable equipment.  Usually the
  > oven remains on all the time to avoid warm up which is often more than
  > 1/2 hour.  
  > 
  > AI4CQ James
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