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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
    • Morse Abbreviations
    • Morse Code
    • Phonetic Alphabet
    • Q Signals
    • RST Signal Report
  • Tech Talk
    • Antenna Gain
    • Antenna Counterpoise
    • Digital
    • Logging Software
  • Amateur Radio, Why?
  • About
    • Privacy Policy
    • Terms and Conditions
    • Request Account
    • Contact
    • Sitemap
    • Advertise
  • Subjects
    • Activities
    • Antennas
    • contesting
    • Connectors
    • Digital Modes
    • EmComm
    • Installations
    • interfaces
    • Introspection
    • Lab Shootouts
    • Miscellaneous
    • mobile
    • NEC Shootouts
    • News
    • Operating Tips
    • power supply
    • Accessories
    • Promoting
    • Propagation
    • Public Service
    • Radios
    • Repair
    • Reviews
    • Safety
    • Software
    • station
    • Test Gear
    • Tomfoolery
    • Whackers

Nelson Antennas 2m rollup antenna review

January 20, 2021January 10, 2021
Nelson Antennas rollup 2m antenna

Review of the smallest portable 2m antenna on the market producing full size dipole performance and stows into your pocket.

Categories Antennas, Reviews Tags 2m, hiking, J-Pole, portable, Slim JIM

Thermal solutions for the Raspberry Pi

October 19, 2020
Argon One Raspberry Pi 4 case inserts showing the machined heatsink pedestals.

Recent metal case offerings from Raspberry Pi enclosure manufacturers help mitigate heat issues when you dare try process-heavy applications including amateur radio spotting servers.

Categories Computing Tags computer, heatsink, openwebrx, raspberry pi, sdr

Diamond Antenna NR770HBNMO with K515SNMO mobile antenna review

January 1, 2021September 30, 2020

After three years of mobile operation, I review the Diamond Antenna NR770HBNMO with appropriate K515SNMO mount including pattern measurements.

Categories Antennas, mobile Tags 2m, 440, 70cm, Diamond, K515, measurement, mobile, NR770HBNMO

Airspy YouLoop LF/MF/HF Möbius Receive Antenna

September 27, 2020September 11, 2020

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.

Categories Antennas Tags airspy, Baluns, LF, MF, Mobius, Moebius, raspberry pi, sdr, shielded loop, small loop, YouLoop

Anatomy of a low frequency aviation radio beacon

January 1, 2021May 18, 2020
Transmitter with its high voltage terminal supply energy to the insulated tower.

Aviation LF/MF beacons provide the opportunity to admire electrically-small antenna design on a macroscopic scale.

Categories Antennas Tags Aviation, beacon, LF, measurement, MF, monopole, tophat

Using AM to explain the value of radio bandwidth

April 25, 2020

Today’s new SDR options and compatible software provide new ways to demonstrate radio technology to the next generation of STEM students.

Categories Miscellaneous Tags Camtasia, Console, rspduo, sdr, sdrplay

Roof-racking VHF antennas on SUV

January 1, 2021April 7, 2020

Thule roof rails increased my VHF antenna mounting options on my Subaru Forester.

Categories Antennas Tags 2m, 6m, 70cm, Aluminum, Diamond, Forester, measurement, Subaru, Thule, VHF

Demo of TDoA using the SDR.hu network

March 11, 2020

Quick demonstration of Time Difference of Arrival (TDoA) technique to correlate a common transmitted signal on multiple receivers to find the transmitter’s location.

Categories Miscellaneous Tags geolocation, gps, sdr

“Effective encryption” effectively debunked

February 2, 2020February 2, 2020

Months of research prove the notion compressed data over ARQ modem techniques is anything, but effective encryption.

Categories Digital Modes Tags modem, NTS, Pactor, SCS, Winlink

VHF magmount vs. hole-mount performance comparison

January 1, 2021January 4, 2020

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.

Categories Antennas Tags mag mount, measurement, NMO, VHF

“Holidays in the Heart” telegraph demo – how educating the next generation is done

September 11, 2020November 28, 2019

Promoting amateur radio means to first promote technology and this American morse demo does just that.

Categories Promoting Tags American Morse, education, telegraph

Will the real PolyPhaser please stand up

January 1, 2021November 17, 2019

One example of a PolyPhaser through panel protector makes one wonder if I have a counterfeit or has QC taken a turn for the worse.

Categories Miscellaneous Tags lightning, measurement, Polyphaser, surges

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

How to win with HF mobile NVIS

October 16, 2019October 14, 2019

Data from W4GO’s Virginia QSO Party operation confirms how well NVIS works from his SUV.

Categories mobile Tags 80m, mobile, NVIS

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

Beach fishing for QSOs with an STL

July 27, 2019July 17, 2019

Add amateur radio to your beach trip keeping in mind family life balance.

Categories Activities Tags 13 colonies, 40m, beach, Elecraft, fishing, Hatteras, KX3, OBX, small loop, STL, Thirteen Colonies

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

Win a repeater from Bridgecom

May 26, 2019

Win a Bridgecom System repeater system.

Categories Miscellaneous

Energizer lithium vs. alkaline batteries

January 1, 2021May 23, 2019
Shows cell voltage of Energizer Lithium and Alkaline battery over time.

Some APRS beacon tests provide data directly comparing the energy performance of Energizer alkaline and lithium AA cells.

Categories power supply Tags AA, APRS, battery, cell, energizer, Energizer Lithium, Energizer MAX, LiFeS2, lithium, measurement

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

Guidelines on what constitutes distracted driving

April 22, 2019April 16, 2019

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.

Categories mobile Tags APRS, distracted driving, Kenwood, LMR, mobile, safety

Effect of shields on ferrites

January 1, 2021April 14, 2019

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.

Categories Antennas Tags banana plug, Fair-Rite, ferrite, measurement, RG-58, S21, type 61

Wireless near-field sensor

July 31, 2020March 20, 2019
Complete probe ready to connect to AUT and WiFi.

Careful selection of quality probes joined with the Raspberry Pi offerings yields a wireless E and H field sensor for accurate antenna analysis.

Categories Test Gear Tags A/D, Beehive Electronics, dipole, E-field, H-field, lithium, measurement, Pi Zero, Pi Zero W, WiFi
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