Good morning from Oregon Top-Band people,
I decided to re-do some previous tests of the common 75 ohm RG-6
cable I use and is used for delay cables in many places for top-band receiving
systems.
I just thought I would share the results of yesterday's tests.
I took a delay cable that I had used in the field here several times. The
temperature in my shack at the time was only 59 degrees measured on the coaxial
cable itself with a non-contact meter.
I did an OS ( Open Short) feed through calibration with minimum loss 50 to 75
ohm conversion pads installed on my VNA. Calibration was done immediately
before each test below, so two calibrations were done.
The cable under test measured 74.59 degrees delay at 1840 KHz initially.
I watched the VNA make 10 sweeps, each about 10 seconds long for 10
observations of phase delay for two cable temperature tests.
This particular cable was imported by the Steren Co. for sale in The USA, part
number 200-931 .
After the first test at 59 Deg. F I chucked the cable into the food freezer
preparing for the second. One and one half hours later the cable surface temp
measured between 20 and 25 Deg. F
Cable loss was -.61 dB at 59 Deg. F, And -.58 dB at an averaged cable
temperature of 23 Deg. F.
59 Deg. F 23 Deg. F
1 - 74.59 DEG -74.60 DEG.
2 - 74.59 DEG -74.60 DEG.
3 - 74.59 DEG -74.60 DEG.
4 - 74.59 DEG -74.60 DEG.
5 -74.60 DEG -74.60 DEG.
6 -74.60 DEG -74.60 DEG.
7 -74.60 DEG -74.60 DEG.
8 -74.60 DEG -74.60 DEG.
9 -74.60 DEG -74.60 DEG.
10 -74.60 DEG -74.60 DEG.
My bottom line conclusion is that for our purposes on the top-bands I no longer
wonder if the cable delay and attenuation remained constant with winter
deployed arrays.
Incidentally, T&B Snap and Seal have been the best connectors here for
repeatability.
Lee Strahan
K7TJR
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