I have a 5/8 wave antenna I use the tuning chart to tune to frequency but I think the antenna is way off so how would I figure out how long it should be.
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Do you have a SWR meter? If not you will need to buy one. Even a cheap radio shack CB meter will work but may not work with anything under a few watts and won't measure power output that well, but works great for checking SWR in a pinch. The lower the SWR reading = the better the antenna is tuned/cut to resonance. SWR should be < 2 on the meter. Anything above 3 is bad.
I tuned to this chart right here www.natcommgroup.com/pdfs/CFM-95SL(c)_manual.pdf I set my antenna to just a little uder 29" I am really close to 95mhz just a little above that & swr is too high I think this comet I have is 100% junk I have talk to a few pirates over the last few yrs & the all say the 5/8 wave comet is junk a J Pole will out prefrom by 40% to 50%
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Looks like I am gonna have to get rid of the 5/8 now I gonna have to build a antenna which fm broadcast antenna can I build with these extra parts 7 whips 1 54" antenna shaft 1 21" antenna shaft 1 mini ground plane
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1/4 wave groundplane antennas work *okay* but if you want the most gain then I agree with voodoo on the jpole/slimjim however those are harder to build. A basic 1/4 wave antenna is nothing more then 5 radials all of the same length (quarter wavelength), one of the radials is obviously your vertical part and the other 4 are the horizontal parts bent down to a slight angle. Here's a quick online length frequency calculator... www.csgnetwork.com/antennagpcalc.html
Groundplane antennas won't give you much more gain over a basic dipole but they do give a lower angle of radiation so it will keep your signal "over the horizon" for longer range. The only advantage is that they are very easy to build and get the job done. You should be able to build it out of your spare parts.
Post by Reverend Bow Voodoo on Mar 8, 2009 14:03:29 GMT -6
J-poles are worth the effort
The do not require a ground plane, are omni-directional, and get out very well.
Darklife is dead on about 1/4 waves... they work great for receiving... and HF stuff, where the antenna is LONG. but for FM, Start with a j-pole.. Mine survived Hurricane Ike on the roof...
Post by Reverend Bow Voodoo on Mar 9, 2009 5:45:17 GMT -6
So don't use copper, use EMT...
Like it says at the bottom of that website:
"I've built my j-poles out of 10ft sticks of 1/2" emt conduit. Drill a 1/4" hole at the place where the "J" goes. Make the "j"out of 1/4" soft copper, Solder it in place thru the hole and add the cable. Cost about $6 using new parts......... Dave, WB5HDS
I plan on building the J Pole the 1/4 wave is to hard can not find the right parts could I use 1/2" & 1" copper pipe I have enough of the 2 size but not enough of one once the jople is build how would you tune it
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Post by Reverend Bow Voodoo on Mar 10, 2009 5:20:06 GMT -6
Yes, you can use any diameter pipe. In fact, the wider the pipe, the wider the bandwidth the antenna will have...
You tune it buy moving the feed point up or down. Google J-pole Antenna and add FM band to your search.
Like Darklife said, get an SWR meter.. or if you really with to build antennas, invest in a MFJ-259B
Well worth the money when home brewing antennas for optimum performance
My first HAM radio project was a Copper J-pole. I live on the NW side of Houston, Cypress area. I hit the Johnson Space Center repeater on 2 meters (146 Mhz) with 50 watts... and the antenna was 2 feet off the ground in my front yard. That was in 1999.. I am still using the same antenna at the house...
I built the j pole 3/4" copper pipe it is up 44ft to 47ft high runnin 4 watts swr is 1.5 and it is only about 15ft from power lines. I get only about 2 mile range I should be getting 5 to 7 mile rang what could be causing the small rang. Pic comming
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