Unknown length of coax with open end T Connector · NanoVNA v 1.01 S CHART Y Max; Auto -30 -35 -40...

Post on 19-Aug-2020

1 views 0 download

transcript

T Connector

Unknown length of coax with

open end

1. A “through” cable connects both ports through a “tee”.

2. Unknown length of coax, open ended, connectect to the tee.

3. Trace should be showing “CH1” in “LOGMAG” format

1. Zoom in using a more narrow range using the first dip frequency as center and a small span.

2. Mouse over the dip and note the exact frequency.

1. Use a wide frequency range to be sure you can see the first “dip”. This is the frequency at which the cable is one quarter wave in electrical length.

1. The (MUCH) easier way.

2. Downloadable app “TLDetails” does all of the calculations and has VF preloaded for all popular coax

3. Set Frequency dial for the dip frequency and adjust “Length” until “Electrical Length” shows 0.25 wavelength or 90 degrees.

117 / Freq / VF1. The easy way

2. VF (velocity factor) for RG-316 coax is 0.695

3. 117 / 102 / 0.695 = 1.65 feet

4. 1.65 feet = 19 inches