How much power is a 300 Ohm Twin-Lead J-Pole capable of handling?
I am a new Ham (got my call sign on 4-28-08), and I am currently using a Yaesu VX-7R HT, but tonight I ordered another radio, a Yaesu FT-1802M for use here in my apartment. I want to build myself a 300 Ohm Twin-Lead J-Pole, but I am unsure of what the power handling capabilities are. I am pretty sure it will be fine for the 5 watts on the HT but will the 50 watts ( should I need to use it) on the FT-1082M be too much? I was a bit disappointed when I was unable to hit the repeater for check-in on my local clubs weekly net last night and I am hoping that the new radio and the antenna will allow me to get out to it next time.
I have an HTX-212 mobile 2M radio here that I have used with my homebrew, cheap, light gauge, 300 ohm, TV tape J-pole on high power which is 45 watts with no problems.
I’ve been told by people who’s opinion I respect that it will handle 500 watts with no problem.
QRO on 2M here is 45 watts so I have never been able to test it with more.
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The el-cheapo twinlead should do 50w, quality twinlead abt 100w.
Welcome to the hobby of Amateur Radio.
Originally Posted by KE5UFH
Go to this site: http://www.arrowantennas.com/ and scroll down the page until you come to J-Poles. The first one listed is a dual bander for 2 meters/440.. Click on the box marked "inst" and the plans and instructions will come up. Everything you need can be bought at Radio Shack and your local home improvement center..
it's entirely a symptom of who you talk to, I know for a fact a cheap twinlead (read the cheapest I could find) jpole has zero issue's with 100w on 2m fm, and I know for a fact the 300 ohm cheap crap handles 450w ssb feeding a vertical on 10m with no issue's whatsoever.
while the twinlead jpole will work for your purposes also consider building a simple 1/4w groundplane antenna out of a rat shack so-239 and a couple metal coat hangers, simplistic, takes 5min to build, and honestly works just as good if not better than most any other cheap omni homebrew while being by far the easiest to get right the first time, you don't really gain much until you start dealing with stacked colinear ant wich are far more work and far larger.
probably the best place to get an idea of whats what in the vast realm of antenna projects for a new guy will be http://www.hamuniverse.com/antennas.html
plenty of quick and easy projects along with some not so quick and easy projects, all with fairly detailed destructions.
Grats on getting your ticket and I hope you enjoy the antenna building.
Last edited by KC7YPJ; 05-01-2008 at 08:09 AM.
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300 ohm Antenna
My experience with 300 ohm twinlead antennas has been good.The most power I ever used was 100 watts.I have gotten better results from ground plane antennas no matter what band.
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Even the cheapest twin-lead (usually 20 AWG stranded wire conductors) should be able to handle a few hundred watts, so there's no reason to be concerned if you are using an H-T or typical mobile type radio.
But be aware that such a wire antenna will have a fairly restricted bandwidth due to the small diameter of the conductors. That's why, particularly for 2 Meters and above, the "Copper Cactus" type of J-Pole (made with 1/2" Copper pipe) is so popular; it will cover much more of the 2 Meter band with a low SWR. In addition, the J-Pole is ideally fed through a balun, not with a direct coax connection. (Note, I said ideally.)
Making a ground plane antenna may be a better choice, depending upon where you will be mounting the antenna.
Congratulations on the new ticket, and welcome to the hobby.
I have very fresh info regarding twin lead antennas, as I just installed a temporary 6 meter folded dipole made from the very lightest TV ribbon line I've ever seen - #24 stranded wire with a ribbon width of about 1/4 inch, marketed for indoor use.
I have this folded dipole strung up horzontally in the clear at about 20 feet. It handles 100 watts CW without overheating during a 30 second "key down" test.
Your 5 watt HT will not challenge a twin lead j-pole, and even a 50 watt 2 meter rig will not burn it up. With that said, I echo the suggestions to build a simple ground plane antenna first. In part because this is an easier antenna to build and mount, but mostly because a j-pole only works well if properly adjusted . . . and properly adjusting one can be a bear for the inexperienced ham. 73 and have fun.
Temporarily at Neenah, WI