[time-nuts] need recomendation for a portable 10mhz reference oscilator

[Rex]

Eric Fort wrote:
> I'm looking for a fairly basic, relatively simple 10 Mhz PORTABLE
> reference (probably quartz based) with enough stability over a period
> of a week of outdoor temp extremes to keep a 47Ghz transmitter locked
> within 100hz  while mountaintop contesting.  Suggestions are
> appreciated.  something that is small and ran off 12 volts dc (car
> battery) would be a definite plus.
>
> Thanks,
>
> Eric
>   
100 Hz accuracy at 47 GHz is a nice goal but probably hardly necessary 
in practice.

What needs to be sought to make contacts on upper microwave frequencies 
is minimizing ALL the uncertainties. The main thing most hams short-cut  
is aiming accuracy. You really need an accurate aiming degree gauge and 
a way to calibrate it to your current operating position. Here in sunny 
California I usually use the sun shadow on my dish, some software on my 
Palm handheld, and a setting of the time on the Palm to a second or two 
to do the aiming calibration of my tripod. If the sun is not clearly 
available, beacons can be used with great accuracy if available. A 
compass can help too, but I think that it is the hardest to get 
accurate. Knowing up and down angles vs horizontal is helpful too.

For frequency I have used a decent crystal OCXO for some years on 10 
GHz. I'm sure it would be fine on 24 GHz or even higher. I just recently 
made my first contact on 47 GHz with a good, but much less accurate, 
reference. I have a friend who has taken out a very nice 10/24 GHz rig 
with his frequency based on a rubidium source. We shared an operation 
spot one day and while talking with him I said I thought that I couldn't 
justify a rubidium vs. my simple decent OCXO for two days of operation. 
There's the battery current consumption and any good xtal's drift over 
this relatively short period is probably too small to really matter in 
finding the average station and making the contact. He agreed.

If you are going for the record contact that cannot even be heard with 
the naked ear, then, yes, it may be helpful to have the resolution 
provided by an atomic source or GPS enhanced receiver. A good xtal-based 
source seems to be the way to go for phase noise if that is important 
and for ham activities that is important.

My thought was to own a decent GPS disciplined source based on a good  
xtal  source. My  search obtained a Z3816A that I picked up a few years 
ago. That is my main local reference. I also have a few rubidium sources 
that I have picked up but haven't yet accurately synced all of them to 
my best reference.

As the time-nuts list influences me, I'll do more to get all my sources 
close to my best reference and then maybe do more to see how they 
compare, but for my ham activities over a weekend, a good OCXO that has 
been set accurately is quite adequate.

The time-nuts list is a great place to learn about all sorts of stuff 
including test equipment. I intend to hang around and learn, even if I 
never push the envelope nearly as far as many here are focused on.