Amateur Radio Station KP4MD
4nec2 Model Analysis of Quadcopter 'Range Extender' Antennas, posted 22 Mar 2022. Aftermarket 2.4 and 5.8 GHz Antennas for Miniature UAV Controllers.
Butterworth 24 MHz Bandstop Filter in an Altoids Tin (Photoblog), posted 24 Jun 2020. Filter to suppress 23-25 MHz RFI in a KiwiSDR.
KiwiSDR and WsprDaemon at KP4MD (Photoblog), posted 22 May 2020. The KiwiSDR and WsprDaemon at KP4MD decodes and uploads WSPR spots on multiple bands simultaneously.
222 MHz Helical Bandpass Filter in an Altoids Tin (Photoblog), posted 24 Dec 2018. A triple tuned bandpass filter for the 222-225 MHz band in an Altoids tin to suppress harmonics and spurious intermodulation emissions.
Tarheel 100A-HP Screwdriver Antenna (Photoblog), posted 28 Mar 2018. Mounting and measurements of a shortened electrical 1/4-wave vertical monopole antenna with a remotely controlled continuously adjustable center loading inductor.
Telonic TS-200A Coaxial Switch (Photoblog), posted 27 Oct 2016. A single pole six position rotary switch with BNC connectors with VSWR <1.1:1, insertion loss < 0.1 dB, and port isolation >70 dB through 1 GHz.
2016 ARRL Pacificon Presentation "Introduction to WSPR", Slideshow presented 15 Oct 2016.
Smart Meter Interference to 902-928 MHz (Video), posted 18 Aug 2016. The uncontrolled proliferation of Smart Meters by utility companies causes increasing illegal interference to licensed users of the ITU Region 2 902-928 MHz amateur radio band.
Review of the CX-3 1000 Watt Coaxial Antenna Switch (Photoblog), posted 06 Aug 2016. The stray capacitance and inductive coupling between the unshielded hook up wires adversely affects the impedance and isolation between the ports of this switch.
Homebrew Coaxial Crossover Switch in an Altoids Tin (Photoblog), posted 19 Jul 2016. The measured port to port isolation surpasses that published in the January 2011 QST review of the MFJ-1703 switch.
Balcony Mounted Buddistick Antenna (Photoblog), posted 30 Jun 2016. Tests with a Buddistick 9.5 foot inductively loaded monopole antenna mounted on a metal balcony rail.
$4 Homebrew 50 ohm Feed Through Terminator (Photoblog), posted 19 Feb 2016. Using a solder type BNC plug, chassis-mount BNC jack and two 100 ohm 1/8 watt resistors. VSWR < 1.18:1 up to 200 MHz.
Preservation of 144 MHz Radio Wave Polarization Sense (Photoblog), posted 26 Jan 2016. A 144 MHz WSPR study demonstrates the preservation of radio wave polarization over a 136 km path obstructed by mountain ranges.
10 MHz Low Pass Filter Performance Test with Oscilloscope (Video), posted 25 Dec 2015. A Rigol DS1102E Oscilloscope is used to test the frequency response of a homebrew 3 pole Butterworth low pass filter for 10 MHz built into Altoids box.
G8JNJ 432 MHz Mixed Mode Helical Antenna NEC Model, posted 04 Nov 2015. Demonstration of NEC-2 GH Helix Card
4nec2 Antenna Modeling of Near Field Antenna Interaction (Video), posted 01 Nov 2015. Demonstration of the effect of near field interaction on the radiation patterns of a magnetic loop and Buddipole antenna on 14 MHz.
Signal Level Measurement with PowerSDR and External Transverters, posted 30 Aug 2015. Using a Wideband Noise Source to Calibrate PowerSDR Signal Level Measurements with External Transverters
U.S. Overseas Territories Amateur Radio License Data, posted 07 Aug 2015. US Territorial Amateur Radio License Statistics Inside and Outside the 48 Continental United States
The Balcony Mounted Magnetic Loop Antenna, posted 12 Jun 2015. A NEC Model Comparative Analysis of Physical Orientation and Performance
Chameleon CHA F-Loop Antenna Parameters: 5-30 MHz, posted 30 May 2015. Antenna Parameters Measured with a Vector Network Analyzer
"10 Watt 50 ohm QRP Dummy Load with 40 dB Attenuator", Posted 28 Mar 2015. Ten watt 50 ohm dummy load (SWR 1.03:1 or better up to 200 MHz) with 40 dB Attenuator in an Altoids box for frequency and power measurements.
Fox Delta FC-3 Frequency Counter and Power Meter Performance (Photoblog), posted 21 Mar 2015. Characterization of measurement accuracy, frequency stability and linearity.
"Sonobuoy Fox Hunt Transmitter", Posted 24 Jan 2015. Arduino Microcontroller and Military Surplus Transmitter Use for Hidden Transmitter Hunts.
"144 MHz Magnetic Loop Antenna for Direction Finding", Posted 10 Jan 2015. Photo Journal
"Frequency Deviation Measurement with an RTL-SDR Dongle", Posted 25 Dec 2014. Frequency deviation measurement using the RTL-SDR as a service monitor.
"Magnetic Loop Antenna Parameters: 7-30 MHz", Posted 20 Sep 2014. Magnetic Loop Antenna Parameters Measured with a Vector Network Analyzer
Comet CF-360 Duplexer: Schematic Diagram and Circuit Analysis (Photoblog), posted 22 Jul 2014.
"Power Pack for Amateur Radio Field Operation", Posted 10 Jul 2014. Low Cost Emergency Power Pack for Field Deployment of Amateur Radio
"Comparison of Flexible VHF/UHF Antennas", Posted 1 Jun 2014. Some Comparative Measurements with the MiniVNA Pro
"An Elliptical Medium Wave Bandstop Filter in an Altoids Box", Posted 24 May 2014. Design and Construction of an Elliptical Medium Wave Band Stop Filter
"MiniVNA Calibration", Posted 23 Mar 2014. Vector network analyzer calibration basics for transmission mode measurements
"50 MHz Halo Antenna & NEC Model", Posted 15 Mar 2014. Construction and Analysis of Halo Antenna for 50 MHz
70 cm 5 Element Yagi Antenna, Posted 10 Dec 2013. Photo Journal
Down East Microwave L432-28HP Transverter, Posted 11 Nov 2013. Photo Journal
"Computer Headset/Microphone Adapter for FlexRadio 1500 and 3000", Posted 6 Oct 2013. PowerSDR Yields Quality Audio with a Low-Cost Computer/Gaming Headset/Microphone
"Interpreting WSPR Data for Other Communication Modes", Posted 29 Aug 2013. Using the Weak Signal Propagation Reporter Network to Estimate Suitability of Radio Propagation Conditions for other Communication Modes
"Calculating Unknown Capacitance and Inductance with miniVNA", Posted 10 Aug 2013. Method using Spreadsheet Data exported from the miniVNA Vector Network Analyzer
"Low Pass Filter for FlexRadio 10 MHz External Frequency Reference (CC) (Video)", Posted 21 July 2013. Design, construction and performance measurement of a 10 MHz Low Pass Filter in an Altoids Box
"An Improvised 100-1300 MHz Discone Antenna", Posted 02 Mar 2013. NEC Model Design and Construction of a Low Cost Omnidirectional Antenna for 100-1300 MHz
"144 MHz Omnidirectional Horizontal Antennas", Posted 05 Jan 2013. NEC Model Comparisons of Stacked Halo, Turnstile and Eggbeater Omnidirectional Horizontally Polarized Antennas for 144 MHz
"The RM Italy KL-145 Linear Amplifier in Digital Mode Operation", Posted 16 Oct 2012. 140-152 MHz Linear Amplifier Performance in WSPR Mode
"Doppler Frequency Shift Observation of the VO-52 Orbiting Satellite", Posted 11 Sep 2012. Application of Amateur Radio in Geophysics
"WSPR Spot Report Analysis Spreadsheet", Posted 21 August 2012. User-defined Chart and Statistical Analysis of Online WSPR Spot Database (Requires Microsoft Excel 2000 or later)
"144 MHz WSPR Propagation Study", Posted 14 June 2012. Observations of VHF Propagation using WSPR
"Building the Elecraft XV144 Transverter Kit", Posted 28 May 2012. Construction of a 28 MHz to 144 MHz Transmitting and Receiving Converter
"A Low Profile 144 MHz Halo Antenna", Posted 23 May 2012. NEC Model Design, Construction and Analysis of Stacked Halo Antennas for 144 MHz
"A Universal HF Magnetic Loop Antenna NEC Model", Posted 16 September 2011. Design of a NEC Model for Small High Frequency Magnetic Loop Antennas
"14-30 MHz Magnetic Loop Antenna", Posted 03 September 2012. Construction of a Compact and Efficient Portable High Frequency Antenna
"Aligning the Henry Radio 30A02 RF Amplifier", Posted 4 September 2011. A schematic diagram and alignment procedure for the Henry Radio 30A02 VHF RF Amplifier
"A Low Pass RF Filter in an Altoids Box", Posted 28 August 2011. Design and Construction of a Low Pass Filter for the Low Frequency RF Spectrum
"Modeling Commercial Amateur Radio Antennas", Posted August 2011. Evaluating the Arrow OSJ146/440 J-Pole, Cushcraft R7 Vertical, Diamond D130J (Icom AH7000) Discone, High Sierra Sidekick Screwdriver and Hamstick Dipole Performance Through NEC Modeling
"Zip Cord Transmission Lines and Baluns", Posted August 2011. An Analysis of a Low Cost Speaker Wire with Common Mode Chokes as a High Frequency Transmission Line
"Antenna System Measurements with the MFJ-202B RX Noise Bridge", Posted March 2011. RX Noise Bridge Calibration and Applications in Antenna and Transmission Line Measurements
"Measuring the MFJ-949B Antenna Tuner", Posted 18 February 2011. Determining the Capacitance and Inductance Ranges of this T-Network Antenna Tuning Unit
"Comparative Antenna Analysis with WSPR", presented 1 March 2011 at River City Amateur Radio Communications Society. Using the Weak Signal Propagation Reporter Network to Compare Antenna Performance.
"Computer Assisted Low Profile Antenna Modeling II", Posted 25 September 2010. Using the 4nec2 program to design a low profile horizontal loop antenna for a limited space backyard.
"HAARP – LWA Moon Bounce Experiment 19-20 JAN 2008", presented 6 February 2008 at River City Amateur Radio Communications Society.
"Computer Assisted Low Profile Antenna Modeling I", Posted 13 June 1998. Using the MININEC program to design attic antennas.
"PET ASCII Output Program for the Timex/Sinclair ZX81", Syncware News, Vol 3:3, January-February 1986. A Z80 machine language program to port ZX81 programs and data to other computers.
"Audio Frequency Counter Program for the Timex/Sinclair ZX81", Syncware News, Vol 3:1, September-October 1985. QZX, Vol 2:11, October 1984. A Z80 machine language program to use the ZX81 as an audio frequency counter.
"Chebyshev/Butterworth Filter Design", Posted 10 July 1998. An IBM BASIC program to design Chebyshev and Butterworth low-pass, high-pass, band-pass and band-stop filters.
"Butterworth Filter Design", QZX, Vol 2:4, March 1984, pp. 3-5. A Sinclair BASIC program to design Butterworth low-pass, high-pass, band-pass and band-stop filters.
"Phased Vertical Antenna Patterns", QZX, Vol 2:3, February 1984, p. 2. A Sinclair BASIC program to print radiation pattern plots for phased vertical antenna arrays.
"Programming for Automated Satellite Communication", ham radio, Vol 11:6, June 1978, pp. 68-71. Algorithm for a satellite locating program for the Texas Instruments SR-52 programmable calculator.
"Un Programa para Rastrear Los Satélites Oscar Utilizando la Calculadora SR-52 de Texas Instruments", Onda Terrestre, Vol 31:1, May-June 1977, p. 10.
"A Simple Bandpass Filter for 439 MHz", A5, Vol 5:3, May-June 1975, p. 30. A tunable stripline filter in a Minibox for ATV.
"Using the BC-645 on ATV", A5, Vol 5:2, March-April 1975, pp. 3-5. Modifying a WWII surplus IFF transponder for amateur TV transmission.