Topband: RG-6 Delay cables

Lee STRAHAN k7tjr at msn.com
Wed Apr 8 23:57:23 EDT 2020


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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