[time-nuts] Need help with Lucent/Symmetricom Z3810AS

Bob Camp kb8tq at n1k.org
Sun Aug 16 21:22:39 EDT 2015


For any sort of GPSDO to do well (not just this one) you really want an outdoor antenna in a good location. 
In Germany, a good location would be one that has a view of the southern sky from due east around
to due west. Ideally you want a view down to within 10 or 20 degrees of the horizon. If it’s blocked over
20% of that range, you can live with it. If it’s blocked over 60% of that range, you are likely to have trouble. 
Yes, a perfect location would “see” 360 degrees and view down to the horizon in all directions. Very few
of us have locations like that (I certainly do not). 

Almost all modern GPSDO's run external antenna. Unfortunately there is less standardization than you might 
hope. Each GPSDO has it’s own favorite antenna gain. In the case of the KS's, you want an antenna with 20 to
30 db of amplifier gain. You also want one that powers up off of +5V. You can find antennas that have 50 db 
amplifiers in them. You can find ones that need +12 to operate. If you have a long coax run, you will need more
amplifier gain to make up the coax loss. 

Distribution amplifiers can be built or they can be bought. The 10 MHz out of these units is nothing fancy. 
There is no reason to spend a lot of money on distribution. The last box I bought to do this was $30 before
shipping. It was designed as a 10 MHz 8 channel (?) distribution amp. It was plenty good enough to do 
what you are talking about. The internal circuits were based on logic IC’s. 

Computers are (unfortunately) an evil we must put up with today. I would suggest digging in the archives
for all of the details of wiring up a USB to RS-422 converter in order to talk to the unit. The connection info and 
the links to the software are all posted back around last Christmas. 


Only one of the two boxes will be in full operation at a time. The idea was that the cell station kept one of them 
in backup mode. Normally REF-1 should be “on” and REF-0 should be in standby. The interconnection cable 
has been the problem on the only pairs I have had issues with. Pulling it out and plugging it back in fixes it 
in some cases. 


> On Aug 16, 2015, at 7:01 PM, Heinz Breuer <hbreuer at debitel.net> wrote:
> Hello,
> I am new to GPSDO and a new member to this list.
> I bought a Lucent/Symmetricom Z3810AS from the source on eBay and powered it up today for the first time. After 11 hours the RFTG-u and REF1 module is still showing "STBY" while the RFTG-u and REF0 module is "ON". 
> Is this ok or should the RFTG-u and REF1 module show "ON" also?
> I am in Germany and currently use an indoor GPS antenna directly behind a large window facing west. Do I need to put the antenna on the roof or wait even longer?
> I did not try to connect a PC to get any status info because I am no computer wizard. In fact I have two left hands regarding computers.
> I want to use the 10MHz output as a reference for my home lab and feed several frequency counters etc. I probably need to build a distribution amplifier and would appreciate any hints.
> vy 73 Heinz DH2FA, KM5VT
> Von meinem iPhone gesendet
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