[Elecraft] crystal oven question
Darrell Bellerive
ve7cla at shaw.ca
Tue Jun 1 18:24:14 EDT 2004
Don,
Thanks for the information. Wow, I would have never guessed that the
oven would use so much current. It is an order of magnitude greater than
I was figuring.
And I hadn't thought about bringing out battery power either.
This really makes me think twice about the transverter. I have an
MFJ-9406 6 metre transceiver, and perhaps should stay with that.
Although, I would expect the K2/XV50 combination to have far better
performance.
I was thinking of permanently attaching the XV50 to the bottom side of
the K2. I figured I would leave a little air space between them for
cooling the K2 finals by mounting spacers where the feet of the K2 are.
Bolt the XV50 lid to the spacers if possible or use some metal strips on
the sides.
I really wish that the K2 had 6 metres built in or as an internal
option. A K6XV rather than a K60XV. Be nice to have an antenna tuner on
six as well
Darrell
On Tue, 2004-06-01 at 14:00, Don Brown wrote:
> 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/K60XV 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
> To: Elecraft Email List
> 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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