i made a 1 j-pole antenna out of 1/2 inch copper pipe tuned for the 160-161 freq range. i followed some directions i found on the internet. i used a so239 connector on the short section and soldered the center connection to the long section. is this correct?. i noticed a couple of other websites that placed the so239 connector to the long section and the center connection to the short end. which configuration is correct. i am not an antenna expert but mine seems to be working pretty good with a bcd996t.
j-pole question
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Don_Burke
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Either will work. I am told that shield to the stub works better, but I have not noticed a difference. All of mine are shield to stub as it make more sense to me to have the hot lead on the big element.nmize said:
additional j-pole question
in order to build the j-pole i followed directions i found on the internet. i used a j-pole calculator and made the antenna for the 160.500 mhz. the antenna seems to be working just fine on my bcd996t scanner. it picks up freq in a lot of different ranges. i followed the calculations in order to attach the feed point to the antena. does this antenna need to be tuned with an swr meter in order for it to be used on a scanner? if so how does one go about tuning the antenna with the swr meter?
thanks for any suggestions or comments.
in order to build the j-pole i followed directions i found on the internet. i used a j-pole calculator and made the antenna for the 160.500 mhz. the antenna seems to be working just fine on my bcd996t scanner. it picks up freq in a lot of different ranges. i followed the calculations in order to attach the feed point to the antena. does this antenna need to be tuned with an swr meter in order for it to be used on a scanner? if so how does one go about tuning the antenna with the swr meter?
thanks for any suggestions or comments.
Hi N Mize and all,
You cannot use an SWR meter to tune an antenna on those frequencies unless you hold an FCC GROL since you need a transmitter to supply the RF. You may consider borrowing an antenna analyzer from a local ham, I don't recall the specifics of the popular brands but one or another should cover the frequency you want to tune it to. When properly tuned there will be a marked improvement in reception over a hit or miss proposition you get from construction diagrams that only put you in the ballpark. I got lucky, ONCE.
Basically the point where the coax is connected in the U section determines feed point impedance or "tuning", resonance is a function of the length of the main vertical section and should be spot on if you cut it to the proper length. There are several variations on a theme so just follow the tuning instructions for the one you built. If you know how to read an SWR meter you know how to use an analyzer, just ignore the fancy stuff and go with what you're familiar with.
I see by the frequency you mentioned you're interested in the railroad segment of the VHF Hi Band so tune the antenna for 161MHz even and you're right where you want to be. Ah, I hear the 6:17 pulling out of the station now, the GP40-PH2CAT notching up and blowing for the crossing. That's NJ Trainset for you, 4 minutes late as usual. (;->)
You cannot use an SWR meter to tune an antenna on those frequencies unless you hold an FCC GROL since you need a transmitter to supply the RF. You may consider borrowing an antenna analyzer from a local ham, I don't recall the specifics of the popular brands but one or another should cover the frequency you want to tune it to. When properly tuned there will be a marked improvement in reception over a hit or miss proposition you get from construction diagrams that only put you in the ballpark. I got lucky, ONCE.
Basically the point where the coax is connected in the U section determines feed point impedance or "tuning", resonance is a function of the length of the main vertical section and should be spot on if you cut it to the proper length. There are several variations on a theme so just follow the tuning instructions for the one you built. If you know how to read an SWR meter you know how to use an analyzer, just ignore the fancy stuff and go with what you're familiar with.
I see by the frequency you mentioned you're interested in the railroad segment of the VHF Hi Band so tune the antenna for 161MHz even and you're right where you want to be. Ah, I hear the 6:17 pulling out of the station now, the GP40-PH2CAT notching up and blowing for the crossing. That's NJ Trainset for you, 4 minutes late as usual. (;->)
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