Good day, all,

Can someone, please, tell me what the *GREEN* trace and the BLACK trace represent on the TDR graph. WHERE on this graph is the length value of coax being measured?

Does anyone know why TDR always, severely, bungles the length value of my coax-under-test, e.g., a 54 foot length is given as 1.77 meters.?

Thanks to all 1st responders.

73 - if apropoe

Phil, *WF3W*

Phil,
Though more recent firmware may vary, take a look at the following message to get some idea on how to set up for TDR:
https://groups.io/g/nanovna-users/message/12494
The time (and length) range depends on how high the frequency range is set.  For long cables, use a lower maximum frequency.
You want a time range that goes up to 200ns or so to allow for the round trip time for a signal on a 54 foot cable; try a maximum frequency of 100MHz or so.
--John Gord

On Mon, Jun 13, 2022 at 10:32 PM, Phil, WF3W wrote:

>
> Good day, all,
>
> Can someone, please, tell me what the *GREEN* trace and the BLACK trace
> represent on the TDR graph. WHERE on this graph is the length value of
> coax being measured?
>
> Does anyone know why TDR always, severely, bungles the length value of my
> coax-under-test, e.g., a 54 foot length is given as 1.77 meters.?
>
> Thanks to all 1st responders.
>
> 73 - if apropoe
>
> Phil, *WF3W*

how did you set up vf?? (velocity factor)??

as far as i know the value is to be set in "percent" .. means a cable
with vf=0.66 neds a setting of 66

dg9bfc sigi

Am 14.06.2022 um 04:45 schrieb Phil, WF3W:

> Good day, all,
>
> Can someone, please, tell me what the *GREEN*trace and the BLACK trace
> represent on the TDR graph. WHERE on this graph is the length value of
> coax being measured?
>
> Does anyone know why TDR always, severely, bungles the length value of
> my coax-under-test, e.g., a 54 foot length is given as 1.77 meters.?
>
> Thanks to all 1st responders.
>
> 73 - if apropoe
>
> Phil, *WF3W*
>