I saved about 30% of the power by encasing mine in polystyrene foam.  I use a ten-turn 1k pot with a 4k7 to ground and another 4k7 to the positive supply to set the fine offset.  I glued the two 4k7 resistors together, then encased them in foam as well because I found that a gentle breeze on one of them would cause significant changes in frequency (OK, I am talking tens of milliHertz, you may not count that as significant).  One of mine was about 150mHz LF without trimming, not sure about the other, but it was very close.  They are both MV89As

Neil G4DBN

On 01/08/2016 19:49, Andy Talbot andy.g4jnt@... [ukmicrowaves] wrote:

 

Apply a fine tune voltage of between 0 to 5V to the tuning pin for fine adjustment.   You don't say which model you have, but I have an older Morion OCXO (roughly 2004 vintage) and that pin offers a few parts per billion of fine tuning - can't recall exactly how many and can't measure it now; it's now built into the 10GHz PortaBeacon.

The heat will be coming from the outer oven, and you will save a bit of power consumption by enclosing in insulation - its not that important.

'jnt

On 1 August 2016 at 19:39, Edward Harland g3vpf@... [ukmicrowaves] <ukmicrowaves@...> wrote:

 

Following the recent discussion on the group about stabilising frequencies using OCXO's I have acquired a Morion double OCXO and have the following questions for those of you who will have more experience of using these devices than I do.

1. The unit runs hot to the touch, I measured 46C, which implies a lack of internal heat insulation. Is the oven performance improved by adding additional external heat insulation such as sheet expanded polystyrene?

2. The unit has a fine tune capability via an externally applied voltage. I assume I can just leave this pin open circuit. If I want to improve accuracy how do I adjust the voltage to get the correct frequency? From comments on the group it would appear the GPSDO short-term stability is not good enough. Any ideas?

Thanks

Ed G3VPF

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