Ecoflex 15 don't bend it too much..
Hi
After having found SWR problems and erratic behaviour of my amplifier at high power levels I started checking the whole antenna system. First I found after calculation that my powersplitter was not exact 50 ohms but "only" 48 ohm. Resulting that it transforms the exact 50 ohm antennas to 46 ohm.. so a mismatch. I build a new splitter with exactly the right dimensions Outer conductor square 32mm inside diameter and inner conductor round 15mm outside diameter. This results in exact 50 ohm.
After replacing it, I terminated it with 4x 50ohm 10W terminators, applied power to it and found a good SWR, but not flat over a large part of the spectrum. On 142 MHz impedance was only 35 Ohm while on 144 it was exact 50 ohm, then on 149MHz another peak. This told me that there is some impedance mismatch in the cable. The first 35m is 7/8 cellflex.. After terminating that piece with 50 ohm SWR was flat form 120 to 160 MHz so it must be the last part of the cable 15m Ecoflex-15 from halfway the tower to the top..
After installing the new powersplitter I also found out there was not enough power at each port. While transmitting 15W in the shack I only got 2.25W on each port so 9W in total. 6Watt loss which is 2.2dB on a calculated 0.9dB traject. so 1.3dB going elsewhere..
Then I found also a "knick" in my cable....
after cutting it and gently opening the cable I was a little bit upset.. My goodness what a mess..
This is the result of 6 years bending the cable just above the last tie wrap. As I have an erectable tower I can't install my cable fixed, when the tower is at fill hight the cable can swing around a bit. This is at the lowest point where the swing is maximum.
This wasn't looking good. I replaced the connector on the remaining piece of cable and measured the power again now getting 12W at the splitter input. So this dirty piece of cable turned into a 1.3dB attenuator.
will replace the Ecoflex-15 with a better quality cable.
After having found SWR problems and erratic behaviour of my amplifier at high power levels I started checking the whole antenna system. First I found after calculation that my powersplitter was not exact 50 ohms but "only" 48 ohm. Resulting that it transforms the exact 50 ohm antennas to 46 ohm.. so a mismatch. I build a new splitter with exactly the right dimensions Outer conductor square 32mm inside diameter and inner conductor round 15mm outside diameter. This results in exact 50 ohm.
After replacing it, I terminated it with 4x 50ohm 10W terminators, applied power to it and found a good SWR, but not flat over a large part of the spectrum. On 142 MHz impedance was only 35 Ohm while on 144 it was exact 50 ohm, then on 149MHz another peak. This told me that there is some impedance mismatch in the cable. The first 35m is 7/8 cellflex.. After terminating that piece with 50 ohm SWR was flat form 120 to 160 MHz so it must be the last part of the cable 15m Ecoflex-15 from halfway the tower to the top..
After installing the new powersplitter I also found out there was not enough power at each port. While transmitting 15W in the shack I only got 2.25W on each port so 9W in total. 6Watt loss which is 2.2dB on a calculated 0.9dB traject. so 1.3dB going elsewhere..
Then I found also a "knick" in my cable....
after cutting it and gently opening the cable I was a little bit upset.. My goodness what a mess..
This is the result of 6 years bending the cable just above the last tie wrap. As I have an erectable tower I can't install my cable fixed, when the tower is at fill hight the cable can swing around a bit. This is at the lowest point where the swing is maximum.
This wasn't looking good. I replaced the connector on the remaining piece of cable and measured the power again now getting 12W at the splitter input. So this dirty piece of cable turned into a 1.3dB attenuator.
will replace the Ecoflex-15 with a better quality cable.
Bekend verhaal. Al mijn ecoflex 15 kabels hebben flink meer demping gekregen na veelvuldig afrollen en weer oprollen na de contest. Inmiddels zijn ze deels al vervangen. En dat is bij de andere contestgroepen niet anders heb ik begrepen. Hier staat een illustratief verhaal: http://www.geekshed.co.uk/ecoflex-15-degradation/
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