Re: beacon frequencies 3 cms


Adrian G4UVZ
 

Bell Hill and KBQ Correlate very closely currently there is less than 50Hz between them CCX is about 200 Hz high today ..as for MCB,,it ismy understanding that it changes with the weather!!

G4UVZ Keeper of GB3KBQ

----Original message----
From : andy.g4jnt@...
Date : 23/10/2018 - 14:50 (BST)
To : UKMicrowaves@groups.io
Subject : Re: [UKMicrowaves] beacon frequencies 3 cms

Rb sources do drift, but I don't think the physics allows them to be off by more than a couple of PPB.  Certainly not hundreds of PPB, unless the cell has failed completely and its OCXO or TCXO is in free run

Bell Hill is GPS locked using a "Simple GPSDO" so drifts a few PPB over tens of seconds.  Long term average, spot on but 6.8Hz high on 'SCX due to DDS 32 bit rounding error.




On Tue, 23 Oct 2018 at 14:40, Richard <richard@...> wrote:
Hi
I'm still using RDDS to lock 3 LO's to a 10 MHz LRPO
I've just fired the microwave stuff up after a long while.
The two beacons I can hear at the moment do not tie up with the last 50
spots
I'm making MCB on .970, it was spotted low but not that low and my
106.5 MHz LO does look a bit low when locked , (well not really locked
dragged close )
But CCX which the last 50 spots show it exactly on frequency I reckon
is high very high around .955
My LO is measuring at 106.499778 MHz  222 Hz error,  21.3 KHz error at
10 GHz.
That means there is another error , I can verify the IF transceiver
accy against beacons on 23cm and lower frequencies.

So questions , what frequency is GB3CCX really on ? 10GHz
What frequency is GB3MCB really on  ?  10GHz

Unfortunately I cant hear the Bell Hill beacon as I suspect Andy keeps
that really close to nominated frequency.

Do Rubidium sources drift with age  ??
I find that hard to believe as its a gas vapour loop, but anything is
possible.
If the Rb has drifted I can compensate the LO frequency with the RDDS
control word.
But I could do with a starting datum point. I don't have a GPS locked
source.
--
 Best wishes /73
 Richard Bown

 Email : richard@...

 HTTP  :  http://www.g8jvm.com

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