Wireless near-field sensor
Careful selection of quality probes joined with the Raspberry Pi offerings yields a wireless E and H field sensor for accurate antenna analysis.
Feedline eliminator test transmitter – first look
The Raspberry Pi Zero brings nearly off the shelf gear to the task of generating an RF test signal from a completely wireless, small, self powered device about the size of a D cell.
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 autotransformer two ways
I take a moment to document observed differences between end-fed antenna autotransformers 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.
Winlink and Modems: When to not cross the streams
Those opposed to Winlink are attempting to hold removal of the 300 baud HF data limitation hostage.
When an N connector isn’t
You would think the world of RF connectors of the pedigree of the “N” would rigorously follow the dictates of the standards that define them. Thankfully most do, but exceptions arise and here is one such example of why it pays to “trust, but verify.”
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.
WWVB DX Virgin No More
Thanks to a spiffy new Airspy HF+ SDR receiver I can scratch listening to WWVB off the bucket list.
MFJ-259 Battery Holder Repair
My MFJ-259 HF/VHF SWR Analyzer required yet another repair to its internal battery holders.
NIST takes aim at WWVB, WWV and WWVH
The National Institute of Standards and Technology appears to have the time and frequency broadcast stations on the chopping block given the info contained in their 2019 budget proposal. This is what I wrote to my senator and congressman.
DX Engineering supports AHVD antenna
DX Engineering supports the build of the Asymmetrical Hatted Vertical Dipole (AHVD) antenna with standard and two custom parts.
When antenna tilt matters
We test a popular VHF/UHF dual band antenna at various angles to reveal antenna tilt on a vehicle matters only in certain circumstances.
The self-absorbed ham
A writer details how his ham father dissed his family by losing himself in technology. The story serves as a canary in the coal mine for “social media” then and now.
NVIS works very well… except when it doesn’t
Near Vertical Incident Skywave (NVIS) propagation works wonders when the bands cooperate, but can slam the door shut at any moment.
Diamond NR770HBNMO vs. Comet M-24M
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.
Radials mitigate feedline and mast currents, tests reveal
Antenna patterns from a Diamond X50NA reveal how radials of proper size mitigate current running down the feedline and mounting structure.