[time-nuts] Racal 9420 OCXO
GandalfG8 at aol.com
GandalfG8 at aol.com
Wed Aug 24 09:13:15 UTC 2011
In a message dated 24/08/2011 00:03:19 GMT Daylight Time,
danrae at verizon.net writes:
Nigel, I took the liberty of correcting the part number in the header.
They are quite common, also quite often go wrong, so beware if you buy
any off ebay...
I don't think Racal released circuit diagrams of any of their ovens. I
have traced out the circuit of the rapid warm up oven found in a lot of
receivers, the 9442-12 and have fixed those, there is a ceramic cap that
frequently goes wonky. The two 9420s I have fixed were just broken
wires; they seem to have used PVC insulated wire which degrades... I
haven't done the homework on those yet.
The 9420s I have do have an EFC input as well as a stabilised Voltage
out to feed it, and in the receivers I have that use it [RA1795] the
fine setting is done from that, coarse setting from the top adjustment.
So yes, in theory they could be used as a basis for a GPS disciplined
standard, but a quick eBay search shows a lot of more modern and
probably better quality 10 MHz OCXOs from China...
--------------------
Whoops:-)
Hi Dan, and thanks for the correction, bit of a silly error considering I
actually had one in front of me as I typed:-)
I've never owned an RA1795 but don't recall the fine tune option being used
in the RA1794 or 1796, despite that table I included, but it's been a
while and I could be wrong.
This 9420 has a base plate still attached and with pins 5 and 6 linked at
the B7G socket, which does seem to imply the EFC option could be available
even if not used in this particular instance.
Thanks for the repair tips, I'll bear that in mind when I get time to
check this one out.
I certainly agree re the more modern 10MHz oscillators, and I don't have a
particular need for another 5 MHz GPSDO anyway, but having been given this
oscillator thought it might be fun to knock something up and see how it
compared to the Rapco 1804M units I've been playing with.
Regards
Nigel
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