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do you have access to another swr meter ?
are you sure your swr meter is able to do 2 mtrs ?

The meter is rated for 140 to 500 Mhz....

I doubt it's faulty since it does give me good readings in the VHF Marine bands....1.2:1 and below, at the upper end of the ham band (148.000Mhz) it's just a hair over 3.1, and at the lower end (146.000Mhz) it's close to 4.1.....

If the weather holds out, a friend is coming over with a pre-assembled and tuned Ringo, we'll pop that up in the exact same spot as this J-Pole to see what happens.....

As always....I'll report my finds here.....

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37OH - SSV - O773H

Sounds to me like you are making this harder than it needs to be. The SWR curve that you are reporting screams of needing a longer element. I'll be shocked if you can't get it to resonate on 2 meters by adding a little at a time and checking your meter.

Do you have a pair of handheld radios you can use? Then you can have one guy make changes to the antenna, and have another guy in the shack with the SWR meter. N9RZD and I have tuned lots of antennas that way. Just make sure not to transmit while the antenna monkey is touching or near the antenna!

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Highlander, NA-821 on 11 Meters.
N9RZF, David on Ham Bands.

Yaesu FT-847, Galaxy DX-2517, President Lincoln, Cobra 150 GTL, Uniden Grant LT.

it was worth a shot ,Highlander and i built two virtually identical
w5gi antenna's earlier this year , and no two standing wave meters gave the same reading with either antenna ,
i agree with Highlander , sounds like it is a bit short then !
dont know if this has been suggested , but you could also try
loosening the feedpoint and slide it up and down and see if that has any
effect .

Don't Give up !!!! this is how you learn !!!!!

73

I may have overlooked it, but I couldn't see any mention of you changing the feedpoint location. That's critical, and as QRN said, measuring with a tape might get you close, but rarely if ever will it get you right where it needs to be. And all antennas/installations are different.

__________________
If you're like everybody else,
you're about average.
73 de K7KBN

I'm aware of the feed point adjustment, and have had it up and down the verticals, and everywhere inbetween, it will change the SWR's, but not low enough.

I did some more research, found some alternate J-Pole information and design drawlings, and discovered that the Bible of all things Amateur Radio is flawed.

That's right folks, the ARRL, and their Antenna Book has the measurements all wrong on the J-Pole, so if you want to build one, don't go by that book.

The ARRL book has the main radiator listed at 56 3/4", the tuning stub at 18 3/4", and the two separated by 1 1/4".

BuckComm has the main vertical at 57 3/4", tuning stub at 19 1/2", and a separation of 1 7/8"

I artificially lengthened the verticals 1" and 3/4" perspectively, and the SWR's dropped significantly, they aren't the 1.1:1 I keep hearing about, but they came way down, I'm now happy, and not afraid to run this radio at full power.

BuckComm also offers plans for building a 6m J-Pole, and a calculator to determine radiator measurements for any frequency, far better and more accurate information than the ARRL Antenna Book that I just wasted 40 bucks on......

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37OH - SSV - O773H

Not in defense on the "Antenna Bible " , but i thought i noticed
in your build the main vertical was 3/4" or 1", and the tuning stub was
a samller diameter , or did it just appear that way because it was older and
had a patina ?

anyway , if you didnt get er figgered i was going to suggest
looking into your original design ,

looks like your heading inthe right direction with it now

73

You got it right, the first one I built came out a 1/2" short on both elements, so I built a second J-Pole that came out to the exact specifications outlined in "the Bible". That second antenna was still too short compared to the other spec's I got from "BuckComm". After artificially lengthening the elements to BuckComm's spec's, the SWR's dropped significantly, which indicates that the spec's printed in "The Bible" are off by an inch on the main radiator, and 3/4" on the tuning leg.
The Bible also suggests a starting point for the tuning clamps @ 4" above the "T" joint, and BuckComm specifies a starting point @ 1 7/8" above the "T" joint.

Presently my second antenna stands at 57 3/4" on the main element, 19 1/2" on the tuning leg, the contact (feed point) at 1 7/8" above the "T" joint, the only spec I haven't changed yet to match the BuckComm spec's is the separation of the two elements, it still stands @ 1 1/4", where BuckComm's spec's ask for a separation of 1 7/8". However, in it's present configuration my SWR readings are far lower than those represented on the original ARRL Antenna Book spec's for the 144 to 148 Mhz band.

This leaves me with the firm belief that the ARRL dropped the ball on this particular design. The rest of the build spec's for other antenna projects may in fact be correct, but after spending 3 days on this, and having the results I obtained, I feel confident in saying The Bible of Antenna Design is flawed.....

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37OH - SSV - O773H

This is going to sound like a 'defense' of the ARRL, but it isn't by any means, please don't take it as such.
There are no 'one' fixed, never changable specifications for a 'J'-pole, or any other antenna for that matter. Most dimensions are variable to some extent, the primary reason being the diameter of the conductor used in the antenna's construction. A 'larger' diameter typically means a shorter length in one instance. Where the nearness of one conductor to the other contributes some particular characteristic that's desired, making the diameter larger can also mean making the separation larger when a 'special' interaction is required. I've seen working 'J'-poles with element separations ranging from only an inch to over four inches (mine's about three inches, give or take a few 16ths). There can be some 'wiggle-room' with anything, antennas included. I still think the ARRL ought'a have said that somewhere though.
The main thing is that it's working, and it sounds like it is, so good! The only thing I'd add, if you haven't already thought of it is to seal the top ends of that tubing. Plumbing can 'rust out', so can antennas. (Believe it or not, you eventually find the same kind of 'crap' in both of them .)
- 'Doc

The Antenna Book also says that for building a dipole, you use 468/f to determine the overall length. This gets you pretty close, but there will still be the need for some fine tuning. Each antenna, each antenna installation, and each antenna builder is different.

Similarly, I just Googled for jpole information and took ten 2m/70cm designs at random. What worked for one was several inches different from what worked for another. Why? Nature of the beast.

__________________
If you're like everybody else,
you're about average.
73 de K7KBN