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Ham Radio . Magnum Experimentum

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

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choke

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

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

Where a choke chokes

January 1, 2021September 20, 2018
N9TAX Slim Jim Antenna choke under test.

I measure one example of a ferrite coax choke for response over frequency to understand its suitability for VHF and UHF.

Categories Antennas Tags choke, common mode, ferrite, J-Pole, measurement, N9TAX, S21, UHF, VHF

This Balun Chokes

January 1, 2021September 27, 2013
Attenuation of wire wrapped around #43 toroid

Jim (K9YC) Brown’s toroid winding recipes provide a superb RF choke balun for 30-10m using RG316 and a #43 toroid.

Categories Antennas Tags AHVD, Baluns, choke, measurement, RG316, toroid

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