More on the cable testing,
Thinking along the lines Rick was I decided to retest the same cable to see
if the results were repeatable.
The original phase shift for both room temperatures was 59 deg. F and 23 deg. F
Results were -74.6 degrees and -0.61 dB to -74.6 deg and -0.58 dB loss warm
to cold.
VNA calibration was used at the start of each test again.
Several hours after that test the room and cable were up to 61 deg. F . The
second round of tests began.
The first test of phase delay matched the early tests with -74.59 to -74.60
degrees again with loss at -0.617 dB. Very close to the original tests.
I decided to add 4 inches of cable to verify small changes in the
readings. The reading then was -74.89 deg with loss of -0.618 db.
After freezing the cable for another couple hours the temp of it was again
average 23 deg. F . Verified with a thermocouple meter and non-contact device.
The cable phase delay was -74.62 deg. with a loss of -0.517 db . This leaves
some question on the loss number. Perhaps some cable tightening issue or
misreading.
I added the same 4 inch cable to the cold cable.
The result was -74.97 deg and -0.582 db loss. Loss matches the original tests.
All this very respectable data with all the connector connecting and
disconnecting and just finger tightening the connectors. I probably should have
torqued them for the best result.
As I mentioned before I think I am going to not worry about significant cable
phase delay and loss changes with temperature.
Regards all and thanks for the tips and the bandwidth, 73
Lee K7TJR OR
On 4/8/2020 1:28 PM, Lee STRAHAN wrote:
> Even if the copper center conductor expands, the way the cable connectors
> are made allows the copper to simply push in the connector past the
> connection point maintaining its physical length.
Very astute. You may have explained this paradox.
I didn't think of this type F effect. Some type N connectors also work this
way.
73
Rick N6RK
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