BOB, the battery operated “beacon” for APRS
I built a prototype APRS beacon, dubbed Thor Hammer (big), to test back-packable APRS 2m beacon concepts.
Beach fishing for QSOs with an STL
Add amateur radio to your beach trip keeping in mind family life balance.
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.
Win a repeater from Bridgecom
Win a Bridgecom System repeater system.
Energizer lithium vs. alkaline batteries
Some APRS beacon tests provide data directly comparing the energy performance of Energizer alkaline and lithium AA cells.
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.
Guidelines on what constitutes distracted driving
Use this 2 second rule to measure when your driving is distracted enough to be of concern to you and others. Holding a microphone is fine, but other aspects of our mobile radios deserve scrutiny.
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.
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 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.
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.