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Ham Radio . Magnum Experimentum

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

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  • Home
  • Radio Shorthand
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    • Phonetic Alphabet
    • Q Signals
    • RST Signal Report
  • Tech Talk
    • Antenna Gain
    • Antenna Counterpoise
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    • Logging Software
  • Amateur Radio, Why?
  • About
    • Privacy Policy
    • Terms and Conditions
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    • Contact
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    • Advertise
  • Subjects
    • Activities
    • Antennas
    • contesting
    • Connectors
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    • Installations
    • interfaces
    • Introspection
    • Lab Shootouts
    • Miscellaneous
    • mobile
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    • power supply
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EFHW

The end-fed half-wave… discussing this is the equivalent of touching the third rail of antenna discussion in the various forums…. second only to “Pactor in ham radio.”

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

Adding 0.05 wavelength wire to EFHW antenna

August 28, 2019
Various dipoles vs. one with 0.05 wavelength wire.

I add a 0.05 wavelength wire to my previous end-fed vs. center-fed dipole tests and plot the results.

Categories Antennas Tags counterpoise, EFHW, end-fed

BOB, the battery operated “beacon” for APRS

August 4, 2019July 29, 2019

I built a prototype APRS beacon, dubbed Thor Hammer (big), to test back-packable APRS 2m beacon concepts.

Categories Portable Tags 2m, APRS, backpack, Byonics, dipole, EFHW, end-fed, hiking, Laird, Larsen, N, NMO, portable, PVC, SMA

Electrically isolated end-fed vs. center-fed dipole radiation

January 1, 2021June 3, 2019
Measured magnetic field in vicinity of no-feedline end-fed and center-fed 10 MHz dipoles.

Testing confirms an end-fed dipole can energize the radiator nearly as well as a center-fed without need of additional counterpoise or other extraneous conductors.

Categories Antennas Tags center-fed, dipole, EFHW, end-fed, half wave, measurement, raspberry pi

Not all mobile antennas are the same

May 18, 2019May 9, 2019

Mobile antennas have been around for decades, but assuming they perform the same is, sadly, a poor assumption as this comparison of Laird and Larsen VHF NMO EFHW aerials reveals.

Categories Antennas Tags 2m, B1322W, EFHW, end-fed, Laird, Larsen, NMO, NMOWB150B

Of end-feds and feed-lines

June 12, 2019March 3, 2019
Grounded EFHW feedline

Simulations suggest end-fed and center-fed half-wave dipoles share sensitivity to various feedline lengths, but in differing and manageable ways.

Categories Antennas Tags 4nec2, autotransformer, counterpoise, dipole, EFHW, end-fed, feedline, NEC, Simulation, transformer

EFHW transformer two ways

May 2, 2019February 12, 2019

I take a moment to document observed differences between end-fed antenna transformer topologies with and without ferrite core materials with a focus on the reactance compensation.

Categories Antennas Tags autotransformer, EFHW, end-fed, ferrite, transformer

Simulating the end-fed half-wave (EFHW) dipole antenna

April 2, 2019February 4, 2019
The end-fed halfway dipole antenna with blowup of transformer.

A NEC model that includes the transformer helix helps demystify the end-fed half-wave (EFHW) dipole antenna using the autotransformer as impedance converter.

Categories Antennas Tags 4nec2, autotransformer, dipole, EFHW, end-fed, EZNEC, NEC, Simulation, transformer

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

EFHW HT antenna functions without additional counterpoise

January 1, 2021September 14, 2018
EIRP measurement of laboratory reference dipole, FT1D stock antenna and MFJ-1714 antenna.

EIRP measurements of the 2m end-fed half-wave HT antenna from MFJ aids understanding a dipole is a dipole no matter where you feed it.

Categories Antennas Tags 2m, dipole, EFHW, EIRP, end-fed, FDTD, FT1D, measurement, MFJ, MFJ-1714, Simulation, Tiger Tail, yaesu

Diamond NR770HBNMO vs. Comet M-24M

February 18, 2020May 10, 2018

The Diamond Antenna NR770HBNMO paired with their K515S insulated luggage rack mount provides measurable and observable upgrade for my 2015 Subaru Forester 2m/440 mobile.

Categories Antennas Tags 2m, 440, 70cm, Comet, Diamond, EFHW, end-fed, Forester, K515, M-24M, measurement, mobile, NR770HBNMO, roof rack, Subaru, UHF, VHF

Displacement Currents

September 17, 2018January 18, 2017
Kirchhoff's current law as boundaries.

Displacement current explains why the ends of dipole antennas have something more than zero current.

Categories Antennas Tags dipole, EFHW, half wave

Of fields and feedpoints

June 14, 2019December 31, 2016

Understanding how feed position along the half-wave dipole antenna affects the electric and magnetic fields around it.

Categories Antennas Tags AA5TB, Balanis, capacitance, dipole, E-field, EFHW, FDTD, Griffith, H-field, high impedance, Kirchhoff, link, link coupling, LNR, Simulation, Terman, voltage

The dipole antenna, how industry defines it

July 8, 2019April 28, 2016
All dipole antennas... according to the IEEE

Is a dipole antenna defined by its behavior alone or also how one energizes it? The answer exists in IEEE and historical literature.

Categories Antennas Tags center-fed, dipole, EFHW, EIA-329, end-fed, half wave, IEEE, offset-fed, TIA-329

EFHW LNR Precision EF-10/20/40MKII Test Data

May 18, 2019April 16, 2012
SWR Measurements of LNR Precision EF-10/20/40 End Fed Antenna

Basic tests of the LNR Precision EF-10/20/40 multi-band portable HF EFHW antenna including S11, SWR and a bandwidth check of the match box.

Categories Antennas, Reviews Tags 10m, 20m, 40m, EFHW, end-fed, half wave, LNR Precision, measurement

EFHW LNR Precision EF-10/20/40MKII Examination

May 22, 2018April 15, 2012
Schematic of LNR Precision 10/20/40 Portable Antenna Matchbox

The background and details of the LNR (Par Electronics) EF-10/20/40 end fed half-wave multi-band portable HF antenna. Come see what’s inside the mysterious “black box.”

Categories Antennas, Reviews Tags 10m, 20m, 40m, EFHW, end-fed, half wave, LNR Precision, NEC, portable, QRP, Simulation

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