Wolf River Coils – Silver Bullet vs. Silver Bullet Platinum 1000
We examine the differences between the original and higher power version of Wolf River Coils’ Silver Bullet 1000 tunable loading coils.
Antennas
Simulations and testing are shown in these articles about ham radio, and a few other, antennas.
Copper efficiency after weathering
I use a weathered copper small transmitting loop to see if copper oxide affects antenna conductivity and hence efficiency.
Nelson Antennas 2m rollup antenna review
Review of the smallest portable 2m antenna on the market producing full size dipole performance and stows into your pocket.
Diamond Antenna NR770HBNMO with K515SNMO mobile antenna review
After three years of mobile operation, I review the Diamond Antenna NR770HBNMO with appropriate K515SNMO mount including pattern measurements.
Airspy YouLoop LF/MF/HF Möbius Receive Antenna
The Airspy YouLoop is a no tune, broadband, small footprint, affordable LF to HF receive antenna that works indoors. Its modular construction facilitates experiments to understand where the Möbius inspired electrical design provides benefit.
Anatomy of a low frequency aviation radio beacon
Aviation LF/MF beacons provide the opportunity to admire electrically-small antenna design on a macroscopic scale.
Roof-racking VHF antennas on SUV
Thule roof rails increased my VHF antenna mounting options on my Subaru Forester.
VHF magmount vs. hole-mount performance comparison
Much has been said about the electrical disadvantages of using a magnetic mount for your VHF/UHF mobile needs. Measurements compare the magmount to a thru-hole NMO mount.
The J-Pole antenna is herewith fixed
For what it’s worth, the myths surrounding the J antenna have been sorted out resulting in an improved version.
Adding 0.05 wavelength wire to EFHW antenna
I add a 0.05 wavelength wire to my previous end-fed vs. center-fed dipole tests and plot the results.
Electrically isolated end-fed vs. center-fed dipole radiation
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.
Not all mobile antennas are the same
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.
Effect of shields on ferrites
A simple S21 test reveals conductive shields do not change the behavior or ability of a ferrite to perform the role of common-mode rf current choke.
Of end-feds and feed-lines
Simulations suggest end-fed and center-fed half-wave dipoles share sensitivity to various feedline lengths, but in differing and manageable ways.
EFHW transformer two ways
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.
Simulating the end-fed half-wave (EFHW) dipole antenna
A NEC model that includes the transformer helix helps demystify the end-fed half-wave (EFHW) dipole antenna using the autotransformer as impedance converter.
Antenna radiator decoupling stub flub?
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.
Where quarter-wave radiator decoupling stubs work… and don’t work
Tests suggest transmission line decoupling stubs are not immune to the conductor past the stub.
J-pole: Where a choke is no joke
Measurements reveal the effects of common mode current on the J antenna.
HT Antenna Comparisons
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.
Fair-Rite 2661480002 Type 61 Ferrite Slide-on Chokes
A closer look at type 61 ferrite material in various configurations for RG58 reveals the benefits and insufficiencies of chokes in series.
Finding facts of Fair-Rite Ferrites
Learning more about several ferrite compositions from the Fair-Rite manufacturer including where to buy them.
Where a choke chokes
I measure one example of a ferrite coax choke for response over frequency to understand its suitability for VHF and UHF.
EFHW HT antenna functions without additional counterpoise
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.