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Need help on How to test transmission line
Hi fellow amateurs,
I am using 746Pro for 6M with direct coax to my 5 el antenna. I used to get 1:1 SWR but recently, the SWR runs a little over 1:2 and my output drops to 30W.When stations in FN20 were working EU, I could hear nothing. My signal can still be received because I was able to make contacts despite 1:2 SWR as far as FM5AA. But I know something is wrong with the line or the antenna. I checked all the connections and they seemed to be ok. Can someone help by directing me to a source where I can read about troubleshooting transmission line? Or can someone who has experience in this give me step by step instruction on how to diagnose the problem, e.g., is it the PL 259 at the rig side, or the antenna side, or somewhere along the line, or is it the antenna altogether. I have an ohm meter and a small swr/pwr meter box. Thanks in advance. 73, steve |
#2
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Need help on How to test transmission line
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#4
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Need help on How to test transmission line
gravity wrote:
"Dave" wrote in message . .. wrote: Hi fellow amateurs, I am using 746Pro for 6M with direct coax to my 5 el antenna. I used to get 1:1 SWR but recently, the SWR runs a little over 1:2 and my output drops to 30W.When stations in FN20 were working EU, I could hear nothing. My signal can still be received because I was able to make contacts despite 1:2 SWR as far as FM5AA. But I know something is wrong with the line or the antenna. I checked all the connections and they seemed to be ok. Can someone help by directing me to a source where I can read about troubleshooting transmission line? Or can someone who has experience in this give me step by step instruction on how to diagnose the problem, e.g., is it the PL 259 at the rig side, or the antenna side, or somewhere along the line, or is it the antenna altogether. I have an ohm meter and a small swr/pwr meter box. Thanks in advance. 73, steve Steve, If you can locate someone who owns an antenna analyzer you should be able to analyze your problem. I use the MFJ 259B. Someone in your local radio club should own one, antenna analyzer, or have access to one. BTW, a 2:1 VSWR is not BAD. It indicates that the antenna is receiving 90% of the available power. However, ICOMs are designed to power down on low to moderate VSWR. Note: I run about 30:1 on 75 meters. what about coax losses at that VSWR? What coax?? I didn't say I used coax. I said I run about 30:1 VSWR on 75 meters. I use 600 ohm open wire tuned feeders. My TL Loss, approximately 150 feet, is measured at slightly over 1 dB. I've been a ham since before coax became commonly used. g |
#5
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Need help on How to test transmission line
if the OP has no antenna or coax problems, he might invest in an antenna
tuner. http://www.ocarc.ca/coax.htm example follows. 100 watt transmitter 30 watts out 50 feet Belden 9913 2:1 SWR 26 watts to antenna Gravity |
#6
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Need help on How to test transmission line
I've been a ham since before coax became
commonly used. g are you bragging about being old? ;-) Gravity |
#7
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Need help on How to test transmission line
gravity wrote:
I've been a ham since before coax became commonly used. g are you bragging about being old? ;-) Before WWII, coax wasn't all that popular. -- 73, Cecil http://www.qsl.net/w5dxp |
#8
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Need help on How to test transmission line
gravity wrote:
I've been a ham since before coax became commonly used. g are you bragging about being old? ;-) Gravity Among other things! Have I told you about my grand kids??? g |
#9
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Need help on How to test transmission line
wrote in message oups.com... Hi fellow amateurs, I am using 746Pro for 6M with direct coax to my 5 el antenna. I used to get 1:1 SWR but recently, the SWR runs a little over 1:2 and my output drops to 30W.When stations in FN20 were working EU, I could hear nothing. My signal can still be received because I was able to make contacts despite 1:2 SWR as far as FM5AA. But I know something is wrong with the line or the antenna. I checked all the connections and they seemed to be ok. Can someone help by directing me to a source where I can read about troubleshooting transmission line? Or can someone who has experience in this give me step by step instruction on how to diagnose the problem, e.g., is it the PL 259 at the rig side, or the antenna side, or somewhere along the line, or is it the antenna altogether. I have an ohm meter and a small swr/pwr meter box. Thanks in advance. 73, steve I presume this is a CushCraft with a Gamma match, and an SO239 connector for the feed. I have a CC 2meter antenna where the SWR shot up. Turned out to be the shell of the SO239 not making good contact with the Gamma bracket. Could also be something loose in the match itself. If you are using the original 9913, it could be full of water. It would also be useful to find out if you still get maximum gain off the front of the antenna. Do a 360 on one of the beacons, and record the S meter readings Before doing anything at the antenna, I would look at the coax and see if there is any visible damage, like from squirrels. The next easiest thing to do is to whack off the PL259 on the radio end, and very carefully install a new connector. Ignore the crap about high SWR being OK. It's not OK for a 6m beam that used to work. Tam/WB2TT |
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