Re: HP 10811-60111 info

David Wrigley <davidwrigley@...>

Hi Conrad

Just noticed your message - (I'm currently diverted with digital video)

I have an HP OCXO on a pcb with a similar number to the one you mention. I
can't see the whole number whilst it's assembled in the rack mounting case.

I have the card assy in my Brooks Shera system.
The card has a divider on it to give 1MHz output as well as 10MHz. I
remember having to change over the division ratio so that I could get a 5MHz
output from it to lock up my Adret. The card was originally wired to divide
by 5 and then by two, so I changed it too divide by two first. The OCXO is
noticeably better than the Toyocom that was originally in the HS400.

If you need the 5MHz facility, I could strip the card out and take some pics
of the mods. Let me know?

The time constant over which you average the error reading in the PLL is
related to accuracy you want to achieve against the speed of the lock. Bear
in mind that if your OCXO is drifting at all you cannot use a long time
constant in the PLL - it will simply lose control. I would recommend that
initially at least start off with quite a short time constant and let the
OCXO settle down - over a period of a week or so. Then you can start to
tighten up the control by lengthening the TC.

This hits on the real problem of using GPS for portable operations - to get
good accuracy it need some time to settle down. For practical purposes
however an hour may provide adequate stability, provided that the OCXO has
been kept powered up.

I have found a Rubidium standard quick and convenient for any tests I have
been conducting - it seems to get better than 1pp10^10 within a few minutes.

David G6GXK

-----Original Message-----
From: [] On
Behalf Of G0RUZ Conrad
Sent: 26 October 2005 19:31
Subject: [ukmicrowaves] HP 10811-60111 info

Hello I recently purchased an HP 10811-60111 OXCO from eBay and would like
to commence work on locking it to GPS. I have a CT1DMK gen-lock board from
John G8ACE and I would like to find a suitable GPS RX. Do they all output 1
pps and if so how lock does it take to achieve stability in practice?

The HP OCXO came on a board marked D42903F 05328-20027 does anyone have
details of this board or at least the connections for the edge connector? I
hope to build a nice reliable 10 MHz source and then lock all my transverter
local oscillators to this. When the crystals arrive I should have OCXOs for
13 and 3cms to start with.


Conrad G0RUZ

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