Wow Evan, That is pretty much what I observed with mine for drift and it is legitimate drift since I set the calibrator to ON and listened to the signal shift in pitch significantly over time. From a cold start I was seeing roughly 500Hz of drift by the digital readout. I also have a fan and it seemed to take a long time to finally settle down.
Like you, I did not test it with transmitting which would heat it up and cool it down and add more variables to the mix. Since I added the DAFC it seems totally solid with no observable drift at all. The DAFC from Conny has the advantage that it is already built and tested and installs out of the way using an existing screw hole. I really wanted to build one but I found it hard to track down a PCB and locate all of the parts for any of the available designs that I could find and then I would have faced trying to figure out how and where to connect it and I got lazy and took the "easy" way out!!! ;-) 73, Mike WA3WOM ----- Original Message ----- From: K9sqg To: [email protected] Cc: [email protected] Sent: Wednesday, September 15, 2010 10:36 AM Subject: [Drakelist] Drake 7 line drift Fellow Drake Enthusiasts, The discussion of the VFO stabilizers prompted me to describe what I have observed about 7 line PTOs over the past 25 years or so. At the risk of offending, I would like to express some observations I have made through tests of my own equipment, TR-7s (over a dozen or so), TR-7As (three), R7s (two), and R7A (one). My experiences have indicated two groups or classes, if you will, of drift characteristics. One set of equipment appears to drift well under 50 hz per hour, while the other set can drift 100-200 hz per hour. Stabilization varies from a few hours to almost 24 hours. Note that I can't be precise since (1) I wasn't using an external counter with known accuracy, (2) the resolution/display of the DR7 is 100 hz, and (3) I didn't make detailed records of all the equipment for archive purposes, from my initial tests. Having said that, let me present one record I did make recently of one of my TR-7As. Frequency was set via the PTO dial approximately midway between the next highest and next lowest 100 hz readouts. The times are Zulu and the frequency was on 40 meters, normal ambient room temperature, from a cold start. No transmit cycles were used. A cooling fan was used to exhaust air from the rear of the rig. 1340 hrs 7258.0 kc 1348 7258.1 1410 7258.2 1425 7258.3 1458 7258.4 1541 7258.5 1551 7258.5 1627 7258.5 1726 7258.6 1838 7258.6 2352 7258.7 0733 7258.9 1208 7258.9 1343 7258.9 1421 7258.9 1528 7258.9 1824 7258.9 From the above observational data, you can see that the PTO did eventually stabilize after about 18 hours or so, for the given TR-7A, in receive only, no transmit cycles. You can see that the initial drift was about 200 hz per hour for the first three hours. The other "class" of PTOs drifts substantially less and stabilizes sooner. I have not done any investigation to see if this observational data correlates with serial numbers on the rigs. In comparison, I have observed that the RV-75 external VFO keeps drift well under the 100 hz resolution of the DR-7 for days at a time, how much I don't know. This email is for informational purposes only and is not meant to offend anybody. I realize your experiences are likely to be different and I present mine for what they are worth. Have a great week and enjoy those Drakes. 73, Evan, K9SQG ------------------------------------------------------------------------------ _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
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