On Wed, 18 Jan 2006 21:59:12 -0600, Didier Juges <[EMAIL PROTECTED]> wrote:
>Tom Van Baak wrote: > >> >> >>>I should be able to improve the receiver performance some by ovenizing >>>it. I wonder if it would be worth the effort? >>> >>> >> >>You can check this with a hair dryer. Measure the effect >>of a 10 C rise and then extrapolate back to 0.1 or 0.01C >>to see what the result of making an oven would buy you. >> >> >> >One problem with that approach is that crystals that are not intended >for oven operation are optimized for minimum frequency change over 0-50 >or some other "normal" environment temperature range, and at 75 degree C >or wherever you are going to run the oven at, the temperature >sensitivity might be much greater than around 25 degrees. So even though >the oven might reduce the temperature variation by a factor of 10 or >better, the overall frequency sensitivity may not improve by the same >factor.. The approach that I've taken in the past is to "room temperature ovenize" the oscillator. That is, put it in an insulated enclosure with a Peltier junction and set up a 4 quadrant PID control loop to maintain the temperature at, say 80 deg F. One of the most successful applications was to an inexpensive frequency counter with a simple TCXO. I applied some RTV to the crystal and oscillator chip for heat conductivity, laid a small Peltier junction and a thermistor in the RTV, then enclosed that area of the board with aerosol spray foam (Great Stuff), along with a similar amount on the bottom of the board. I set the control point to 80 degrees. After aging for a couple of years, that counter settled down to be one of my most stable, despite costing less than $200. I brought out a test point so I could monitor the power to the Peltier. Even when using the counter in a hot 2-way radio shack, the temperature remained precisely at 80 deg. My main curiosity with the GPS is whether there are other stabilization methods employed that would make ovenizing moot. john --- John De Armond See my website for my current email address http://www.johngsbbq.com Cleveland, Occupied TN A foolish consistency is the hobgoblin of little minds.-Ralph Waldo Emerson _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
