[time-nuts] T.I. experimenting - newbie question

[J. Forster]

I would not trust the VOP of any coax cable of a non-precision types.
Generally, if you need that kind of precision, you use air line or hard
line and measure it with a TDR.

-John

=============



> If I understand you correctly, then I did not have things setup
> symetrically. Now I have a tee on each of the A and B inputs. The
> unused port on the B tee has a 50 Ohm terminator. Is this what you
> mean?
>
> With the above setup, using the shortest cable I have gives me 1.5 ns.
> Adding the longer cable to the shorter, using a F-F BNC coupler gives
> me 21 ns, for a difference of 19.5 ns. The readings are bouncing
> around a bit, so these numbers aren't exact. Using the 19.5 ns figure
> and a 66% VOP, I get 3.86 M, which is much closer to the measured
> length.
>
> If I use the calculated length vs the measured length, I get a VOP =
> 65%. Pretty close to the specified 66%.
>
> Thanks to everyone for the help. Any more hints or discussion are
> always appreciated.
>
> Joe Gray
> W5JG
>
> On Sat, Apr 2, 2011 at 8:55 PM, Hal Murray <hmurray at megapathdsl.net>
> wrote:
>>
>> You want the difference in path lengths.  Is there an asymmetry in the
>> setup?
>>  If so, count the BNC connectors that don't have a match on the other
>> path.
>>
>> If you have input-Tee-coax-Tee-terminator, then the difference is the
>> coax
>> plus half of each Tee.  That is you want to measure the length from
>> center of
>> Tee to center of Tee.
>
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