[time-nuts] 0MHz distribution...NOT

[Chuck Forsberg WA7KGX N2469R]

On 03/10/2012 04:44 PM, Mark Spencer wrote:
> I've done this as well.
>
> I daisy chained several pieces of hp and marconi gear together that all had an approx 1k ohm input impedance for the frequency reference and fed them from a single 10 Mhz source via t connectors with a 50 ohm terminator at the end of the line.   Looking at the signal with either a scope or a time interval counter I have seen noticeable phase shifts when some of the equipment receiving this signal is turned off or on.   That being said so long as the equipment was not turned off or on the adev of the signal was as expected.   Your mileage may vary.
>
> Sent from my iPad
>
> On 2012-03-10, at 4:24 PM, Michael Blazer<mblazer at satx.rr.com>  wrote:
>
>> You may want to take a look at the signal on a scope.  Most instruments terminate their reference input.  You might actually have 4 50 ohm loads on the Thunderbolt's output and the input voltage might be marginal.  If your instruments have both reference input and output, it's better to daisy chain the units.
>>
>>
>> On 3/10/2012 5:10 PM, Chuck Forsberg WA7KGX N2469R wrote:
>>> A month or two ago I had sketched out a simple distribution amp
>>> for my 10 MHz reference.   In the meantime I became somewhat
>>> disillusioned about my FE-5680a standards.   So I removed the
>>> FE-5680a and disconnected its power supply from the box that
>>> holds the Thunderbolt, power supply, and big line filter.
>>>
>>> I decided to try daisy-chaining the Thunderbolt's 10 MHz output.
>>> I have plenty of hardware left over from the days of 10BaseT networking.
>>>
>>> So I have the Thunderbolt going to a BNC T on the back of my FlexRadio 1500,
>>> hence to my Advantest U3641 spectrum analyzer, and finally to the external
>>> reference on my Racal-Dana 1992 nanosecond universal counter.  That end
>>> has a 50 ohm termination on the other side of its T connector.
>>>
>>> All three devices seem happy with the 10 MHz they are receiving.
>>>
I connected my Tek 2712 to the end of the chain.  It reads +10dbm +-1db.

Switching units on/off/ext ref causes less than 1db change in the 10 MHz.


-- 
Chuck Forsberg WA7KGX N2469R     caf at omen.com   www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
   Omen Technology Inc      "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231   503-614-0430