[GPS_Standard] Replacement 10 MHz Oscillators

[Zack Widup]

The Isotemp OCXO's have outstanding stability from my experience.  They 
are sufficient as stand-alone references for microwave LO's through 10 
GHz.  Another microwaver friend of mine has used the Isotemp 136 as the 
reference for his 24 GHz station as well and says he experiences less than 
50 Hz frequency drift at that frequency. That would indicate a stability 
of around 0.02 Hz at the 10 MHz reference frequency.

I have noticed a similar stability, about 20 Hz at the 10 GHz frequency.

What I have used the GPS standard for is as a reference to align the 
OCXO's for better accuracy before I go out into the field.

73, Zack W9SZ

On Thu, 8 Nov 2007, Bert, VE2ZAZ wrote:

> Hi P M,
>
> I am afraid this kind of stability will not be good enough for long term
> control. Remember that the end-to-end electronic tuning range on the HP
> units is 1Hz! GPS Systems will disciplin these oscillators for a few years
> before requiring re-alignment with the adjustment screw. A 10Hz end-to-end
> range will still work with my GPS-Derived Standard design. I have not tried
> a wider tuning range though. Regardless, this would mean that after a few
> hours you would lose the ability to disciplin your oscillator.
>
> Designing a good OCXO is a very challenging task... You need to understand
> the physics of crystals. Selecting the right crystal cut and optimal
> operating temperature requires knowledge beyond most hobbyists's abilities.
> You also need to promote the right oscillation and reduce the spurious ones.
> I leave this to experts. There is nothing wrong about trying though... And
> besides, I don't know your level of expertise. :-)
>
> Have fun...
>
> Bert, VE2ZAZ
>
> ----- Original Message -----
> From: "P M Gant" <ha5rxz at gmail.com>
> To: <gps_standard at mailman.qth.net>
> Sent: Thursday, November 08, 2007 3:15 PM
> Subject: [GPS_Standard] Replacement 10 MHz Oscillators
>
>
> I have spent the last week experimenting with replacement homebrew
> oscillators for use in the GPS standard. After some work I now have a
> fixed 10 MHz oscillator that drifts less than 3 Hz per hour after warm
> up, this unit is single ovened but well insulated from the outside
> world.
>
> My next task is to turn this unit into a OCXO so I am looking for tips
> about the recommended +/- frequency spread, control voltage and types
> of varicap to use. All suggestions are welcome.
>
> HA5RXZ