[time-nuts] problem with Efratom FRS-C from eBay

Ed Palmer ed_palmer at sasktel.net
Sat Oct 18 00:55:52 UTC 2008

Three things you can check are:

1.  How close to 10 MHz?  I bought an FRK-L a while back that wouldn't 
lock.  I was able to watch the frequency sweep up and down as it tried 
to find the Rb frequency.  The sweep takes about 40 sec. to complete a 
cycle.  It turned out that the xtal had aged to the point that it wasn't 
even getting up to the right frequency and the coarse tuning adjustment 
didn't have enough range.  A quick change of the value of an internal 
tuning capacitor fixed it right up.  You need to have about 8 or 9 
digits on your counter to see the sweeping.

2.  What's happening to the crystal monitor voltage?  Similar to the 
above, you should be able to see it rise and fall as the system tries to 
find the Rb signal.

Normally, this kind of sweeping action means that the Rb signal is weak 
or dead.  So.....

3.  What's the lamp monitor voltage?  The FRS-C should be >= 6V.  My 
FRK-L is spec'ed at >= 7V.  Mine locks down to about 5.4V.


> Hello all,
> My FRS-C showed up today.  I carefully wired it up and powered it on.  I got
> a nearly 10MHz signal out.  The frequency counter is dancing around a bit
> and I get a 0.02 V on the lock indicator line after about an hour warm up.
> Specs show this should happen in under 10 minutes and it looks like it is
> not locking.   Dead unit?
> I obtained it from this ad:
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290262243079
> The unit that I received does not show TTL after the frequency and the scope
> output looks like a cross between a sinewave and a ringing square wave.  I
> have about 13 feet of RG174 between the FRS and the measurement equipment so
> who knows.   This is the "*Rubidium and GPS DO From
> China<http://stores.ebay.com/Rubidium-and-GPS-DO-From-China>"
> *eBay store, which I thought was pretty reputable so I want to make sure I'm
> not doing anything wrong before I contact the seller, PayPal, etc.*  *There
> was also a big white sticker covering the whole top of the unit.  I had to
> remove it to verify the pinouts and the model information.  Hoepfully that
> didn't void my warranty on the $100 paperweight.  Should I let it sit
> overnight?  Any suggestions would greatly be appreciated.
> Thanks,
> Bob, N3XKB

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