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bad coax symptom..
- Thread starter Splash1
- Start date
Sounds like water has been in the line to me. Maybe not still there, but over time water can contaminate the shield. The way the Imax and A99 type antennas connect to the feed line---makes them prone to letting water in the feed line. The
Starduster antenna was also prone to this problem.
One way to tell if the line is the problem before you cut it open to look, is to put a dummy load and a meter at the far end of the coax and then check how much watts are getting thru the line. If the line is 50-100 feet it should show at least 90% or more getting thru to the end. Another common indicator of water damage is a broader bandwidth than normal. If you are seeing a really flat SWR over the frequency range of you radio then suspect water problems. Feed lines like 9913 can also be prone to water problems when exposed to the weather.
Starduster antenna was also prone to this problem.
One way to tell if the line is the problem before you cut it open to look, is to put a dummy load and a meter at the far end of the coax and then check how much watts are getting thru the line. If the line is 50-100 feet it should show at least 90% or more getting thru to the end. Another common indicator of water damage is a broader bandwidth than normal. If you are seeing a really flat SWR over the frequency range of you radio then suspect water problems. Feed lines like 9913 can also be prone to water problems when exposed to the weather.
I think I would hesitate to say the coax is bad. If the meter readings haven't changed drastically, "but dont seem to be getting out like i have befor" may just be propagation. Of course from what you've said, the coax mmay be bad, but I would expect those readings to change too.
- 'Doc
- 'Doc
Hello Splash1:
Good points made here by the others. I have seen some fiberglass none ground plane antennas have ice or water in the base of the antenna where the matching circuit is, throwing off the match some. And of course rusty connections by none stainless steel hardware can cause bad electrical connections. These rusty connections can be fixed by wire brushing the old hardware, or better yet replacing then with the stainless steel type hardware. And in some cases after cleaning, applying Black RTV Silicon Rubber to seal the connections and Coax.
Shaking the Antennas Mast during receiving or transmitting and having some one watch a SWR Meter or S-Meter at another station is a good check.
The bad thing about the PL-259 Connectors is that they are NOT water tight or even water resistance. So the PL-259 Connectors have to be sealed from the water and moisture. I use Black electrical tape, or shrink sleeving and Black RTV Silicon Rubber.
And once water gets into you coax the shield wire will turn in color and the insulator the dielectric will change its value causing in time more and more "Insertion Loss" in the Coax.
And the NOT soldered to great PL-259 Connector always seems to be out there. The PL-259 Connectors causing problems I have seen are the ones that do not have the shield wire soldered, or poorly soldered.
If it is the coax causing the reduced field strength in received signals, and transmitted signals, it can be easily checked by some simple test equipment.
See: FAQ: What about the Coax
NOTE: The second diagram should show the watt meter at the very end of the coax under test. Not on the radio end of the coax.
The are coax specification tables showing the coax loss in 100 feet lengths, and it should be not be to hard to measure the loss of the coax and check the loss in the Coax Loss dB specification chart.
Jay in the Mojave
Good points made here by the others. I have seen some fiberglass none ground plane antennas have ice or water in the base of the antenna where the matching circuit is, throwing off the match some. And of course rusty connections by none stainless steel hardware can cause bad electrical connections. These rusty connections can be fixed by wire brushing the old hardware, or better yet replacing then with the stainless steel type hardware. And in some cases after cleaning, applying Black RTV Silicon Rubber to seal the connections and Coax.
Shaking the Antennas Mast during receiving or transmitting and having some one watch a SWR Meter or S-Meter at another station is a good check.
The bad thing about the PL-259 Connectors is that they are NOT water tight or even water resistance. So the PL-259 Connectors have to be sealed from the water and moisture. I use Black electrical tape, or shrink sleeving and Black RTV Silicon Rubber.
And once water gets into you coax the shield wire will turn in color and the insulator the dielectric will change its value causing in time more and more "Insertion Loss" in the Coax.
And the NOT soldered to great PL-259 Connector always seems to be out there. The PL-259 Connectors causing problems I have seen are the ones that do not have the shield wire soldered, or poorly soldered.
If it is the coax causing the reduced field strength in received signals, and transmitted signals, it can be easily checked by some simple test equipment.
See: FAQ: What about the Coax
NOTE: The second diagram should show the watt meter at the very end of the coax under test. Not on the radio end of the coax.
The are coax specification tables showing the coax loss in 100 feet lengths, and it should be not be to hard to measure the loss of the coax and check the loss in the Coax Loss dB specification chart.
Jay in the Mojave
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