So Im reading about these J-pole antennas. Has anyone made one with good results?
copper or aluminum did you use?
looked at the chart on building one and seems simple.
One person selling them but they are fixed made to freq of you choice with a band with of 4 mhz so i guess it would be 2mhz either side of say 90 my guess would be have one made for 90 will cover 88-92mhz.
Seems the 2 measurements of A and B if they could be made to slide up and down you could make this do all the bands 88-108 just follow the length chart.
Think I will try this dipole made of copper need about 15 feet and 1 elbow.
Just gotta figure how to get the correct size for 2 pieces of copper to slide inside each other to tune the antenna.
Maybe a 1/2 inch into a 3/4 inch would have to slot the end of the 3/4 and tighten with stainless hose clamps like i have seen in other pictures. Well got some time to hunt up some copper and see what happens.
Please if anyone has done this please chime in with any advice please.
J-pole antennas work well if you can manage the common mode currents which plague end fed antennas.
There are multiple opinions on what works best but one of the best guides I've read along with actual measurements on feed point/coupling comes from AA5TB. Sadly the site looks down at the moment of writing this but there are hundreds of other websites discussing in great detail how to use them on VHF and above.
At the end of the day the EFHW (J-pole included) is no better than a regular center fed dipole. It comes down to which is easiest to mount in your location. In fact results from a J-pole may actually suffer over that of a dipole because of lossy coupling and unknown effects of the pole or tower it's mounted to unless it is completely isolated, and even then the coax will make up for the "other side" of the antenna so to actually radiate.
That said, I have had good success with J-pole style antennas on VHF and even UHF. They tend to be more useful on the HF bands in my opinion since it makes for a far easier mounting location instead of dead center of the dipole. Most antenna analyzer software shows that it's best to mount the center coax conductor to the longer leg of the J and the ground to the shorter leg portion to reduce CMC and improve radiation pattern. Indirect coupling using coils will even further reduce common mode currents along the coax which a member here talked about in a thread years ago but I lost track of which post.
As far as the bog standard dipole it will be up to you to get creative. For high power handling I've used thin conduit before to make each leg telescopic and clamps to find the resonant spot then simply drilled through each sliding leg and bolted them solid. Sure it wouldn't be much more work to do the same with a J. Don't waste money on copper unless you really insist on soldering the tubing together.
For lower power you can get away with something as simple as CB antenna stainless steel spring loaded whips without their base and cut them to length, mount each "leg" of the dipole on PVC and to the coax lugs, tidy up with RTV sealant and use the set screws on each whip to fine tune. Mounting bracket will have to be DIY too of course. Can never have enough U-bolts for this sort of stuff Hell I've seen people use old TV rabbit ears and seal them up in PVC before. You'd be surprised what will work with lower power.
Usage of a common mode choke, even with some rolled up coax can help if you get RF feeding back into your equipment room.
Was just lookin to talk around 88-96 fm broadcast band and get about 5-10 miles with an adjustable 50 watt transmitter. Antenna will be about 35 feet up. Was looking for an omni directional at least 1/2 to 5/8 Are not the dipoles more directional.
Maybe a good ground plane will do the job thats why I asked here to see what some are using with decent distance and strong signal so no stereo dropout.
Only if they are horizontally polarized in which case they will take on a figure 8 pattern.
When vertical they act omnidirectional unless mounted in the middle close to another metal object like a supporting pole which can act as a reflector and screw the pattern some. Most pirates on the FM broadcast band go for vertical polarization anyways since most listeners will be in cars with vertical antennas.
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