[time-nuts] Trimble Thunderbolt and David Partridge divider board question

Bob Camp kb8tq at n1k.org
Mon Oct 12 16:18:09 EDT 2015


The 10 MHz out of the TBolt is pretty much straight off the internal OCXO with only modest
buffering. If the whole TBolt dies, you still get a clean looking 10 MHz out. Best guess
is that the problem is in the divider board. 

That said, it’s RF overloading a system. The RF could easily be coming in through the 
TBolt and that’s the point that the fix (RF isolation) needs to be applied. It’s also quite 
possible that it’s coming back up the lines that are connected to the divider. 

Simple approach to debug the issue (check to see if the problem is there after each step):

1) Pull the antenna off of the TBolt, it will still work fine with no antenna.
2) Pull any serial cables off of the TBolt
3) Disconnect any cables off of the divider that aren’t needed for the TS-590.
4) Add a big fat ground strap between the TBolt and the divider
5) Add a big fat ground strap between the divider and the TS-590
6) Minimize the cable length between the TBolt and divider, same with divider and TS-590

If you have made it this far with no fix, chokes on the power supplies are the next step. 


> On Oct 12, 2015, at 10:08 AM, Chris Wilson <chris at chriswilson.tv> wrote:
>  12/10/2015 14:58
> I have had my Trimble and Dave's divider board for many years and it's
> on 24 hours a day, seven days a week, no problems.
> https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAAahUKEwjr27ewjb3IAhVMVhQKHVmJALI&url=http%3A%2F%2Fwww.perdrix.co.uk%2FFrequencyDivider%2FFrequency%2520Divider%25202.1.pdf&usg=AFQjCNHiXeXt-NZksvMBKYHfkJPf5mn_Fw&sig2=YJooGHWI_easGkSZHUVPJgThe
> Trimble uses a mushroom roof mounted aerial. I have recently built up
> an amateur band 136Khz station giving about 800 Watts into a terribly
> inefficient (electrically very very short) Marconi T aerial witha
> horizontal wire loop capacitive top hat. I have used the 10MHz out of
> Dave's divider board to lock a master oscillator in my Kenwood TS-590
> transceiver, which is the driver for my 136kHz amp, giving just 0 dBm
> out. I have found when the TX is on at 136kHz the Trimble / divider
> baord output goes wild and a clean square wave goes seemingly random
> on my scope with noise. This unlocks the TS-590, blah blah.
> My  questions  are,  is this likely to be RF affecting the Trimble, or
> the  board?  the  baord  feeds  a  panel  in my shck with its vearious
> frequency  divisions,  the  10MHz  output  goes  to the Kenwood TS-590
> reference  locking  gizmo.  The  scope shows noise from a disconnected
> RG-316  co-ax  at  the  panel end. Should I get up in the loft and try
> connecting  the  10MHz direct from the Trimble and leave the board out
> as  a  test?  Does  anyone know if a strong 136kHz signal is likely to
> affect the Trimble itself?
> Thanks.
> -- 
>       Best Regards,
>                   Chris Wilson.
> mailto: chris at chriswilson.tv
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