[time-nuts] frequency reference for portable operation

Mike Seguin N1JEZ n1jez at burlingtontelecom.net
Sun Mar 10 11:02:19 EDT 2013


Hi Jim,

There are a few different schools of thought. Here in New England, I use a 
very simple GPS locked 10 MHz oscillator. It's based on the Jupiter GPS 
series with 10 kHz out. It drives a Qualcomm 1152 MHz board. This board 
generates harmonics through 24 GHz.

I don't lock any of my rigs up to 24 GHz. From 47 GHz and up (78, 122, 241 
GHz) the rigs are locked mostly using Axtal Axiom 75 series OCXO's and GPS 
via VE1ALQ reflock boards.

For my rigs up to 24 GHz, I use the Qualcomm board to generate accurate 
markers. From there, I can adjust my IF to compensate. The simple GPSDO 
driving the Qualcomm is accurate to about 2 Hz/GHz, so even at 24 GHz, I'm 
typically within about 50 Hz - well within my narrow CW filter on the IF.

The added benefit of using the GPS is I have it hooked to an ON4IY RoverBox. 
This gives me grid square, and Sun position based on location/time for 
aligning my dish (if the sun is out...)  Plus the simple GPSDO is locked and 
running in about 3 minutes or so from a cold start.

I find I don't need "ultimate" accuracy from 24 GHz down. And not messing 
with the crystals in LO's keeps phase noise down etc...

We've started to add Panadpaters to our IF rigs lately using the FUNCube SDR 
initially and now the cheaper sticks. These let us see 96 kHz or better at 
once, so finding the signal can be pretty easy.

Remember, locking is great if both ends are locked. If not, you're back to 
tuning around to find the signal (that's where the panadapter is great!)

KT1J and I did our first 2 km 122 GHz contact a while back. We were both 
locked and had rifle scopes calibrated for aiming. It was amazing to point 
our dishes and start sending and instantly hear the other station with no 
tuning!

73,
Mike, N1JEZ
"A closed mouth gathers no feet"


----- Original Message ----- 
From: "Jim Lux" <jimlux at earthlink.net>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Sunday, March 10, 2013 10:23 AM
Subject: [time-nuts] frequency reference for portable operation


> Asking here on behalf of a friend..
>
> With respect to portable amateur microwave operation.. you want good close 
> in phase noise (so you can use narrow band filters) AND good frequency 
> accuracy (so you can find the signal)> 




More information about the time-nuts mailing list