[time-nuts] Comparing PPS from 2 GPS units
Jim Lux
jimlux at earthlink.net
Tue Dec 18 05:52:00 UTC 2012
On 12/17/12 9:40 PM, Hal Murray wrote:
>
> jimlux at earthlink.net said:
>> You mean RG65 http://www.awcwire.com/ProductSpec.aspx?id=M17/
>> 34-RG65-Coaxial-Cable or RG186 http://www.awcwire.com/ProductSpec.aspx?id=RG1
>> 86-Coaxial-Cable
>
> Interesting stuff. Thanks.
>
> RG-65 says no longer available. It also says:
> Coaxial Delay Line 0.15 uSec/ft
> (Am I having troubles counting zeros, or is that seriously slow?)
Yes, seriously slow.. 150 ns/ft, vs 1ns/ft in free space..
> Nom. Imp. 950
> Vel. of Prop. 2 (no units)
> Cond. Material Magnet Wire Helix
> (What is "magnet wire", and what does "helix" mean and how does it effect
> coax?)
>
>
> RG186 says:
> Shield Material Magnet Wire [What does that mean?]
> Nom. Imp. 1000
>
> The cable on scope probes (at least fancy ones) has a tiny conductor. I
> think that translates into high impedance.
>
No.. this stuff has a helically wound center conductor (so the L per
unit length is very high).. impedance is sqrt (L/C) so the Z is high
(1000 ohms).. prop velocity is 1/sqrt(LC), so big L means slow prop..
This stuff is incredibly lossy..
Some of it has the center conductor wound around a soft iron core wire
to increase the inductance.
>
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