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Ham Radio . Magnum Experimentum

Antennas, experiments, engineering and other articles of interest to radio folks.

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Search Results for: j-pole

The J-Pole antenna is herewith fixed

January 1, 2021November 14, 2019

For what it’s worth, the myths surrounding the J antenna have been sorted out resulting in an improved version.

Categories Antennas Tags EFHW, end-fed, J-Pole, measurement

J-pole: Where a choke is no joke

November 10, 2018November 10, 2018
Ladderline J-pole with and without feed-line choke

Measurements reveal the effects of common mode current on the J antenna.

Categories Antennas Tags choke, ferrite, J-Pole

Slim Jim vs. Traditional J-pole Antenna

February 27, 2022August 19, 2015
Measured gain of SlimJIM and J-Pole

Real measurements of a Slim Jim antenna and traditional j-pole antenna reveal the truth about their respective gain and pattern.

Categories Antennas Tags 5/8 wave, copper, dipole, HFSS, Hoverman, J-Pole, Lindenblad, measurement, NEC, Simulation, Slim JIM

Mast Mountable J-Pole Antenna

December 8, 2017June 17, 2015
Overview highlighting novel features of mast mountable j-pole antenna.

The J-Pole antenna’s long and storied design history is due for one more chapter to mitigate the longstanding mast current and reliability issues.

Categories Antennas Tags inductance, J-Pole, Simulation, stub, UHF, VHF

Have your J-Pole and ground it too

September 24, 2018February 27, 2015
1.06 GHz Test J-Pole Antenna

Tame the predictable mast currents found in any j-pole antenna grounding conductive mast using a simple stub. Shown is empirical evidence why this is a problem and a very simple solution all future grounded j-pole antennas should incorporate.

Categories Antennas Tags 1 GHz, folded balun, Grounding, J-Pole, lightning, mast, measurement, NEC, Pawsey Stub, Simulation, stub

J-Pole Antenna – Should I ground it?

September 24, 2018January 28, 2012
Impedances competing for current in a J-Pole

To function as intended, the J-Pole antenna needs RF electrical isolation from its mount. Here’s why and in technicolor no less.

Categories Antennas Tags FDTD, J-Pole, Kirchhoff, Simulation

5/8 Wave J-Pole vs. 1/2 Wave J-Pole EZNEC Shootout

November 3, 2018July 9, 2009

We examine if 5/8 Wave J-Poles are better than 1/2 Wave J-Poles.

Categories Antennas, NEC Shootouts Tags 1/2 wave, 2m, 5/8 wave, J-Pole

Collinear 5/8 wave J-Pole vs. Collinear 1/2 wave J-Pole EZNEC Shootout

November 3, 2018July 7, 2009

Another 5/8 J-Pole Design arranged as a Collinear… can it justify the complexity and extra materials?

Categories Antennas, NEC Shootouts Tags 2m, 5/8 wave, collinear, EZNEC, J-Pole, NEC, Simulation

Can a 2m J-Pole be used at 440?

March 5, 2015December 17, 2008

Analysis to suggest you really can use a 2 meter J-Pole in the 70cm band.

Categories Antennas Tags 2m, 70cm, J-Pole

1/4 Wave Monopole vs. 1/2 Wave J-Pole EZNEC Shootout

November 3, 2018November 6, 2008

Myths abound concerning how J-Poles do so well. Here is an EZNEC shootout between a 2 meter J-Pole and a Monopole with radials.

Categories NEC Shootouts Tags 2m, Cebik, EZNEC, J-Pole, monopole, NEC, Simulation

Copper J-Pole Antenna on Play Set

May 23, 2018November 1, 2008

Can a 2 meter J-Pole antenna work well on a child’s playset? Read and find out.

Categories Antennas Tags 2m, Baluns, J-Pole, MFJ, mount, verticals, VHF

Nelson Antennas 2m rollup antenna review

January 20, 2021January 10, 2021
Nelson Antennas rollup 2m antenna

Review of the smallest portable 2m antenna on the market producing full size dipole performance and stows into your pocket.

Categories Antennas, Reviews Tags 2m, hiking, J-Pole, portable, Slim JIM

Antenna radiator decoupling stub flub?

February 18, 2019December 29, 2018
The pursuit of the single half-wave at 3rd harmonic.

Measurements and analysis suggest why quarter-wave stubs fail to completely isolate radiator conductors on multi-band antennas including the popular rollup 2m/440 J-Pole products. Possible improvements are shown.

Categories Antennas Tags 2m, 70cm, choke, coaxial choke, collinear, dual-band, inductance, J-Pole, NEC, portable, resistance, Simulation

Where quarter-wave radiator decoupling stubs work… and don’t work

January 1, 2021December 28, 2018
Choked dipole of varying lengths with demarcations of max current and voltage.

Tests suggest transmission line decoupling stubs are not immune to the conductor past the stub.

Categories Antennas Tags choke, multi-band, parallel, quarter-wave, Simulation

HT Antenna Comparisons

January 1, 2021October 21, 2018

Does one really need to upgrade the antenna that came with your HT? Presented are EIRP measurements of various aftermarket HT aerials to help understand the trade space.

Categories Antennas Tags 1/2 wave, 1/4 wave, Diamond, EFHW, EIRP, FT1D, measurement, MFJ, MFJ-1714, Tiger Tail, yaesu

J antenna and variations thereof

February 22, 2018February 21, 2018
J antenna an variations thereof

There are many ways to morph the basic J antenna into useful forms.

Categories Antennas Tags collinear, J, J-Pole, Slim JIM, Super J

J Antenna Design Patent Grant

September 23, 2018October 10, 2017

USD798847S1 showcases one more incremental step towards a J antenna that works with masts and feedlines.

Categories Antennas Tags J-Pole, patent

Mast Mountable Antenna Patent Application

November 6, 2018July 22, 2017
Front view of Mast Mountable Antenna

The “mast mountable antenna” patent application is now available to review and critique.

Categories Antennas Tags J-Pole, patent

Antenna pattern plots: Good intentions vs. good data

January 1, 2021May 31, 2016
Just say no to handcrafted data graphs

In the 21st century should we believe antenna graphical gain data based on hope and hearsay? J-pole antenna gain drawings are a common bad example.

Categories Antennas Tags G2BCX, J-Pole, measurement, Slim JIM

SlimJIM and Antenna Gainflation

June 21, 2018May 26, 2016
E-plane gain plots of J antenna variations

Understanding why SlimJIM antenna aficionados hype the gain in their marketing and discussions.

Categories Antennas Tags collinear, G2BCX, J-Pole, measurement, NEC, Simulation, Slim JIM

Mast Mountable J Antenna Patent Pending

September 23, 2018January 14, 2016
Section View of Low Impedance Feed

A new j-pole patent? We will see.

Categories Antennas Tags J-Pole

Radials and their far field effects

May 28, 2016January 14, 2016
H-plane gain of monopole with 1, 2 and 3 radials

Radials are peculiar things worthy of some explanation.

Categories Antennas Tags far field, NEC, radials, Simulation, symmetry

The Coaxial Dipole

April 16, 2019February 26, 2014
Coaxial Dipole

G4CQM provides details on a Yagi-Uda coaxial dipole driver approach for designers lusting after a 50 ohm self-balancing feed.

Categories Antennas Tags Coaxial Dipole, dipole, G4CQM, Simulation, yagi-uda

Repeaters, Antennas & Trigonometry

February 22, 2014February 20, 2014

You need an antenna with energy at high take off angles to hit the hill top repeaters… right? Well, not likely. Let’s review the details and do the math to understand what’s needed for VHF terrestrial radio communication.

Categories Antennas Tags 1/4 wave, 2m, 5/8 wave, 70cm, Aviation, repeater, UHF, VHF
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