I recently discovered the J Pole antenna. I've never used one but I'm thinking that it'll make for a pretty simple mobile base antenna for my 2m/70cm Yaesu.

Anyone ever use one?

I have one I used to use.  Someone on here recommended it.  Basically very simple.  I was in a rental and couldn't go sticking up big antennas, so I just stuck this in the ground in the yard, and ran a 2m off of it.  Actually worked very well.

I am far from an expert so I'll let the more knowledgeable folks chime in.

My setup was very much like this, but was just stuck into the ground.

I use one.

It does what I need done.

I have a commercially made Arrow J-Pole. It is very light weight, has very little wind load.

I built a "copper cactus" J-pole back when I was on VHF. Rugged and worked very well. The gain is about the same as a quarter wave ground plane antenna.

A practical construction article will give you a better idea of what you'll be dealing with: http://www.n7qvc.com/copper-cactus-dual-band-super-j-pole-antenna-project/

I'm using an Arrow J pole. I also have one of Ed Fong's DBJ-1 that I use out at the camper and also as a backup encom antenna.
Both I would have no problems at all recommending.

Yes I built one and use it for 2m. Works really
great.

I've been using them for decades, all home brew and very easy to build.

I have the B-Square Engineering 2m/70cm stainless J-pole.

Works well!

I built an Ed Fong DBJ-1 from the QST article about a year and a half ago (you can also buy them from Ed on ebay).   It is basically a dual band j-pole made from twin lead wire.

It is a great performing antenna but, true to fashion, I decided I wanted something better.  Consequently I bought a Diamond X-50N, expecting it to outperform my twin lead antenna POS that was built after a bit too much bourbon.  I was mistaken.  Because I run FSQCall 24 hours a day, seven days a week I have a lot of .csv data files to parse and understand the 2 meter propagation variance from my station and after crunching four months of data, the DBJ-1 outperforms the Diamond significantly.

As soon as I can get back on my roof the DBJ-1 is going back up and the Diamond is for sale.  Yep, J-Poles work even though you'll see threads with religious fervor that claim they cannot.

My first antenna was a N9TAX roll up j-pole that I bought.  
I still use it.  It's been hanging up in a pine tree for the last 3 years.  Works fine with my ft-7800 for the local repeaters.
I'm about to buy 2 more.  For RACES mobile work.  Because they work.

You have a defective antenna, feedline, connector or something.

Since you have data collection, build a 1/4 wave ground plane and compare it to the wire J pole, for scientific curiosity.

I haven't seen anyone claim that a J pole can't work, just that they aren't the antenna miracle that some claim, and in fact suffer some issues in real world performance.

Yep.  Have a copper tube version and build roll up versions out of window line on a pretty regular basis.  Cheap, easy to build and work well.  Not magic just a good basic design that scales to various frequencies well.  There several good Slim Jim/J Pole measurement calculators out there, here's one of many:




 

I thought the same thing, I went back over everything and there was no change of anything except the antenna itself.  I simply removed the dbj-1 and put the diamond in its place.  I double checked the connectors and the feedline just in case.  The SWR on the Diamond is better and flatter than the DBJ-1 but in terms of real world performance, by measured SNR over the course of several weeks, the DBJ-1 is outperforming the Diamond.  The only thing I can attribute to it is that in my location, along with the locations of the stations I am meshed with, that perhaps the DBJ-1 has an optimal take off angle for my situation.

Building a 1/4 wave is a good idea just for the sake of comparison.

Trust me, I wanted it to be better.  I spent $100 on it, it just wasn't.  :-)

N9TAX roll-up with 16' lead and BNC Male (Love it!)
Ed Fong PVC (own 2) flawless
Arrow J-pole (on chimney) perfect

I prefer the N9TAX for portable
I prefer Ed Fong for Base Use
Ed is now making a tri-band (2m, 440, 220)

I've also built this for APRS use
Carl's Big Stick

Got a link for the tri-band version?

Very very interesting.

The antenna Box of Truth

Interesting propagation research using WSPR mode on 2M and 70 cM can be found here --->  https://groups.google.com/forum/#!forum/2-meter-wspr   and is fascinating reading for nerd-headed hams.

A bottom line - VHF propagation varies greatly by the hour, by the day, by the month, with weather, with temperature, with season, etc....

IOW, one can not draw a whole lot of meaningful conclusions about antenna performance unless the data is taken at the same time  in comparison to a reference antenna, or in a A/B/A/B manner that nulls out changes in propagation and distills out the antenna's relative performance.

When measuring one antenna for some length of time, then swapping to another for some length of time, it's not impossible to determine if changes are due to antenna performance or due to propagation.

IOW a J-pole even at it's best (which is NOT often the case if you go by some of the crummy designs on the web) has a few dB less gain than a properly designed and implemented colinear.

The good news is that the dual-band version of the J-pole with the center section coaxial stubs AND with the ferrite choke at the base are fairly decent antennas, and my measurments show decent radiation patterns and low common mode curent on the coax shield.

Most or all other J-pole designs have the coax shield radiating, distorted radiatin patterns, and tweeky SWR.  The antenna is usually usable, but is not very close to optimum.  W8JI has a good tech page on this issue ---> http://www.w8ji.com/end-fed_vertical.htm

If you're lucky, you end up with a design that's a few 1/10s of a dB away from a 1/4 wave ground plane.  If you're not, you end up with ugly power wasting lobes --->

I've built several Arrow-style dual band j-poles for friends and they all work great.  I use on on top of five sections of surplus aluminum mast sections at the apartment.  I also have a Comet CX-333 and I can't tell the difference.

U have to contact him directly



ETA: corrected the mess my phone made...Anyone interested in buying, I will IM you his Phone #

I have the Blackbird dual band jpole at home and the Ed Fong roll up in my truck. They work well. It turns out that buying the Blackbird was cheaper than buying the tap, die and materials to build my own.

I've seen articles declaring that the quarter-wave ground planes have better performance than the jpoles, but I have not tried it myself.

My dead-simple 1/4 wave ate my J-poles lunch and made it cry.



I am gonna run it back up at similar height as the 300A and see who wins.

I appreciate all the info gentlemen! I'm looking forward to using this antenna!

I built a few J-Poles over the years, this has been my experience as well.  The J Poles have always seemed to be a bit more finicky to get a good SWR.  A good 1/4 wave with ground plane has always seemed to have better SWR for me.

I have an MFJ-1740 stashed up in my attic (HOA) that has performed very well across a lot of different frequencies and works well for my needs.

Many/most of the antennas out there aren't actually J poles. If it's not a shorted stub at the bottom, it's really an open sleeve antenna and will be picky as to element diameters and spacing, etc, plus the missing ground plane.