KA7OEI's blog

Recent posts indexed from this public source.

• The Comcraft CTR-144 FM transceiver - A "multi-mode" solid state 2 Meter transceiver from the early 1970s.
• The Morrow CM-1 receiver - A relic of the cold war's effect on amateur radio
• A new push-pull switch/potentiometer for the Heathkit HM-102 VSWR/Wattmeter
• Making LED headlights RF-quiet
• Replacing the relays in the Yaesu FT-480R (FT-280)
• A (simple) WWVB loop amplifier for radio-controlled clocks
• Repairing a ("smoked") MFJ-998 1.5kW automatic antenna tuner
• Modifying the MFJ-5008 parabolic ultrasonic receiver for better sensitivity and wider frequency response
• Impedance matching (auto) transformer and common-mode choke for the JPC-7 dipole and other electrically-short (loaded) dipoles and verticals
• How I prevented QRM to HF reception from my solar charger and AC inverter at Quartzfest
• Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 3 (of 3)
• Adding ALC and overdrive protection to the MFJ ALS-500M "500 watt" amplifier
• A "sharp" 160 meter receive-only band-pass filter
• DXing distant SolarEdge PV optimizer modules (or long-distance propagation of PV system QRM)
• Exploring the Ameco PCL-P Nuvistor cascode preamp/preselector
• Reducing RF susceptibility for the HamGadgets "Ultra Pico Keyer" - and mimizing RF issues on portable HF stations in general
• A 15 (and 10) meter high-pass filter for Field Day
• The construction of a hybrid ring combiner: Using the same duplexer, feedline and antenna for two repeaters/links/transmitters
• Refurbishing a CIR Astro 200 HF amateur band transceiver
• Using a PIR to reduce wear and tear on a Nixie clock
• Repairing a NanoVNA "V2" with nonsensical readings ("Blown up" input)
• Ali Express "SDR TX/RX Switch" - A design NOT well thought out...
• A short-term capacitor-based "UPS" for mini (NUC-type) PCs
• Charging LiFePO4 batteries from a vehicular electrical system - the problems and a solution.
• Frequency response of the RX-888 SDR at the high and low ends (Above 30 MHz, below 1.5 MHz)
• The "Universal TCXO" - better stability for the Kenwood TS-590, TS-570, TS-480 (and other radios) using the QRP Labs ProgRock 2
• Hiking and POTA (Parks On the Air) operation from Arches National Park (US-0004)
• Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 2 (of 3)
• Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 1 (of 3)
• Rewinding the stainless steel coils with silver-plated copper wire on the JPC-7 and JPC-12 antennas
• Reducing QRM (interference) from a Renogy 200 watt (or any other!) portable solar panel system
• Observations, analysis and modifications of the JPC-12 vertical antenna
• Repairing a dead RX-888 (no A/D converter clocking)
• Analysis of interference from a SolarEdge PV (solar) electric system.
• Using an external clock with the RX-888 (Mk2)
• Repairing a dead Kenwood TS-850S
• Reducing RFI (Radio Frequency Interference) for a POE (Power Over Ethernet) camera or wireless access point
• Remote (POTA) operation from the Conger Mountain BLM Wilderness Area (K-6085)
• "TDOA" direction finder systems - Part 2 - Determining signal bearing from switching antennas in software.
• A simple VHF notch cavity from scraps of (large) Heliax
• Observations, analysis and field use of the JPC-7 portable "dipole" antenna
• Multi-band transmitter and monitoring system for Eclipse monitoring (Part 1)
• Remote (POTA) operation from Canyonlands National Park (K-0010)
• Resurrecting my FE-5680A Rubidium frequency reference
• Measuring signal dynamics of the RX-888 (Mk2)
• Improving the thermal management of the RX-888 (Mk2)
• A solid state replacement for an old radio's "vibrator" (Wards Airline 62-345)
• Modifying an "O2-Cool" battery fan to (also) run from 12 volts
• It *is* possible to have an RF-quiet home PV (solar) electric system!
• Characterizing spurious (Harmonic) responses of the SDRPlay RSP1a (and other models)
• Exploring the "1-930MHz 2W RF Broadband Power Amplifier Module for FM Radio HF VHF Transmission" found on EvilBay
• Injection locking cheap crystal "can" oscillators to an external source
• "CQ CQ - Calling all dielectric welders!" (Or, those strange curvy things seen on a 10 meter waterfall)
• A 2 meter band-pass cavity using surplus "Heliax"
• Exploring the NDK 9200Q7 10 MHz OCXO (Oven-controlled Crystal Oscillator)
• An LCD Retrofit and color display for the Schlumberger SI 4031 Communications Test Set
• Using an inexpensive PT2399 music reverb/effects board as an audio delay (for repeater use)
• An ultrasonic superheterodyne receive converter (e.g. "Bat Listener")
• Using an ATX computer power supply to run KiwiSDRs - and as a general purpose 5 and 12 volt supply
• Making a "Word Metronome" for pacing of speech
• Improving my ultrasonic sniffer for finding power line arcing by using MEMs microphones
• The use case for a blinking infrared LED
• Fixing a TS-570G (The tuner couldn't find a match, timing out...)
• Implementing the (functional equivalent of a) Hilbert Transform with minimal overhead
• High power Tayloe (a.k.a. Wheatstone) absorptive bridge for VSWR indication and rig protection.