corpus.blog
41554 blogs · [ { "id": "01a0bb46-68ba-702d-97e7-4a64f1584b2c", "title": "The Comcraft CTR-144 FM transceiver - A \"multi-mode\" solid state 2 Meter transceiver from the early 1970s.", "url": "https://ka7oei.blogspot.com/2026/09/the-comcraft-ctr-144-fm-transceiver.html", "published_at": "2026-09-16T17:35:28+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1dd1d79e2", "title": "The Morrow CM-1 receiver - A relic of the cold war's effect on amateur radio", "url": "https://ka7oei.blogspot.com/2026/08/the-morrow-cm-1-receiver-relic-of-cold.html", "published_at": "2026-08-15T15:29:01+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1dda83418", "title": "A new push-pull switch/potentiometer for the Heathkit HM-102 VSWR/Wattmeter", "url": "https://ka7oei.blogspot.com/2026/07/a-new-push-pull-switchpotentiometer-for.html", "published_at": "2026-07-28T02:40:38+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1de137f2b", "title": "Making LED headlights RF-quiet", "url": "https://ka7oei.blogspot.com/2026/07/making-led-headlights-rf-quiet.html", "published_at": "2026-07-12T15:20:56+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1de1841b1", "title": "Replacing the relays in the Yaesu FT-480R (FT-280)", "url": "https://ka7oei.blogspot.com/2026/05/replacing-relays-in-yaesu-ft-480r-ft-280.html", "published_at": "2026-05-27T17:02:10+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1de7217ae", "title": "A (simple) WWVB loop amplifier for radio-controlled clocks", "url": "https://ka7oei.blogspot.com/2026/04/a-simple-wwvb-loop-amplifier-for-radio.html", "published_at": "2026-04-12T03:53:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1df007bc1", "title": "Repairing a (\"smoked\") MFJ-998 1.5kW automatic antenna tuner", "url": "https://ka7oei.blogspot.com/2026/03/repairing-smoked-mfj-998-15kw-automatic.html", "published_at": "2026-03-18T16:25:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1df2bda68", "title": "Modifying the MFJ-5008 parabolic ultrasonic receiver for better sensitivity and wider frequency response", "url": "https://ka7oei.blogspot.com/2026/03/modifying-mfj-5008-parabolic-ultrasonic.html", "published_at": "2026-03-04T17:55:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1df2e242b", "title": "Impedance matching (auto) transformer and common-mode choke for the JPC-7 dipole and other electrically-short (loaded) dipoles and verticals", "url": "https://ka7oei.blogspot.com/2026/02/impedance-matching-auto-transformer-and.html", "published_at": "2026-02-26T02:00:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1df7aea8d", "title": "How I prevented QRM to HF reception from my solar charger and AC inverter at Quartzfest", "url": "https://ka7oei.blogspot.com/2026/01/low-qrm-solar-power-and-hf-at-quartzfest.html", "published_at": "2026-01-23T16:40:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e01894c3", "title": "Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a \"IN-13\") \"Nixie\" - Part 3 (of 3)", "url": "https://ka7oei.blogspot.com/2025/12/neon-bar-graph-vswrpower-meter-using-13.html", "published_at": "2025-12-25T18:03:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e0e45867", "title": "Adding ALC and overdrive protection to the MFJ ALS-500M \"500 watt\" amplifier", "url": "https://ka7oei.blogspot.com/2025/11/adding-alc-and-overdrive-protection-to.html", "published_at": "2025-11-28T04:11:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e1dc8981", "title": "A \"sharp\" 160 meter receive-only band-pass filter", "url": "https://ka7oei.blogspot.com/2025/10/a-sharp-160-meter-receive-only-band.html", "published_at": "2025-10-26T17:05:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e28d0a4a", "title": "DXing distant SolarEdge PV optimizer modules (or long-distance propagation of PV system QRM)", "url": "https://ka7oei.blogspot.com/2025/09/dxing-distant-solaredge-pv-optimizer.html", "published_at": "2025-09-10T23:08:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e374fb1e", "title": "Exploring the Ameco PCL-P Nuvistor cascode preamp/preselector", "url": "https://ka7oei.blogspot.com/2025/08/exploring-ameco-pcl-p-nuvistor.html", "published_at": "2025-08-24T20:28:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e4441983", "title": "Reducing RF susceptibility for the HamGadgets \"Ultra Pico Keyer\" - and mimizing RF issues on portable HF stations in general", "url": "https://ka7oei.blogspot.com/2025/07/reduced-rf-susceptibility-for.html", "published_at": "2025-07-29T01:39:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e44bb597", "title": "A 15 (and 10) meter high-pass filter for Field Day", "url": "https://ka7oei.blogspot.com/2025/06/a-15-meter-high-pass-filter-for-field.html", "published_at": "2025-06-13T19:14:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e4a333b5", "title": "The construction of a hybrid ring combiner: Using the same duplexer, feedline and antenna for two repeaters/links/transmitters", "url": "https://ka7oei.blogspot.com/2025/06/the-construction-of-hybrid-ring.html", "published_at": "2025-06-04T17:01:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e5489a03", "title": "Refurbishing a CIR Astro 200 HF amateur band transceiver", "url": "https://ka7oei.blogspot.com/2025/05/refurbishing-cir-astro-200-hf-amateur.html", "published_at": "2025-05-02T15:16:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e5544e23", "title": "Using a PIR to reduce wear and tear on a Nixie clock", "url": "https://ka7oei.blogspot.com/2025/04/using-pir-to-reduce-wear-and-tear-on.html", "published_at": "2025-04-08T16:20:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e5c6639b", "title": "Repairing a NanoVNA \"V2\" with nonsensical readings (\"Blown up\" input)", "url": "https://ka7oei.blogspot.com/2025/03/repairing-nanovna-v2-blown-up-input.html", "published_at": "2025-03-14T23:04:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e6994902", "title": "Ali Express \"SDR TX/RX Switch\" - A design NOT well thought out...", "url": "https://ka7oei.blogspot.com/2025/02/ali-express-sdr-txrx-switch-design-not.html", "published_at": "2025-02-16T20:52:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e78092ba", "title": "A short-term capacitor-based \"UPS\" for mini (NUC-type) PCs", "url": "https://ka7oei.blogspot.com/2025/01/a-short-term-ups-for-mini-nuc-type-pcs.html", "published_at": "2025-01-27T04:01:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e86d9134", "title": "Charging LiFePO4 batteries from a vehicular electrical system - the problems and a solution.", "url": "https://ka7oei.blogspot.com/2024/12/charging-lifepo4-batteries-from.html", "published_at": "2024-12-28T18:11:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e901541c", "title": "Frequency response of the RX-888 SDR at the high and low ends (Above 30 MHz, below 1.5 MHz)", "url": "https://ka7oei.blogspot.com/2024/12/frequency-response-of-rx-888-sdr-at.html", "published_at": "2024-12-04T20:00:00+00:00" }, { "id": "01a08793-39fc-70ad-9936-53e1e9ca983e", "title": "The \"Universal TCXO\" - better stability for the Kenwood TS-590, TS-570, TS-480 (and other radios) using the QRP Labs ProgRock 2", "url": "https://ka7oei.blogspot.com/2024/11/the-universal-tcxo-better-stability-for.html", "published_at": "2024-11-25T17:09:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893c2b7fdf", "title": "Hiking and POTA (Parks On the Air) operation from Arches National Park (US-0004)", "url": "https://ka7oei.blogspot.com/2024/10/hiking-and-pota-parks-on-air-operation.html", "published_at": "2024-11-01T04:16:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893cb95e7d", "title": "Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a \"IN-13\") \"Nixie\" - Part 2 (of 3)", "url": "https://ka7oei.blogspot.com/2019/12/neon-bar-graph-vswrpower-meter-using-13.html", "published_at": "2024-10-01T04:46:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893d88e9be", "title": "Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a \"IN-13\") \"Nixie\" - Part 1 (of 3)", "url": "https://ka7oei.blogspot.com/2024/08/neon-bar-graph-vswrpower-meter-using-13.html", "published_at": "2024-08-28T21:14:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893dd34c03", "title": "Rewinding the stainless steel coils with silver-plated copper wire on the JPC-7 and JPC-12 antennas", "url": "https://ka7oei.blogspot.com/2024/07/rewinding-stainless-steel-for-silver.html", "published_at": "2024-07-31T15:55:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893ea4ebec", "title": "Reducing QRM (interference) from a Renogy 200 watt (or any other!) portable solar panel system", "url": "https://ka7oei.blogspot.com/2024/06/reducing-qrm-interference-from-renogy.html", "published_at": "2024-07-01T05:54:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893ed16d5a", "title": "Observations, analysis and modifications of the JPC-12 vertical antenna", "url": "https://ka7oei.blogspot.com/2024/05/observations-analysis-and-modifications.html", "published_at": "2024-05-29T17:34:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8893fae2d8a", "title": "Repairing a dead RX-888 (no A/D converter clocking)", "url": "https://ka7oei.blogspot.com/2024/05/repairing-dead-rx-888-no-ad-converter.html", "published_at": "2024-05-15T18:21:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88940295a6a", "title": "Analysis of interference from a SolarEdge PV (solar) electric system.", "url": "https://ka7oei.blogspot.com/2024/04/analysis-of-interference-from-solaredge.html", "published_at": "2024-05-01T04:04:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88940e02ce1", "title": "Using an external clock with the RX-888 (Mk2)", "url": "https://ka7oei.blogspot.com/2024/03/using-external-clock-with-rx-888-mk2.html", "published_at": "2024-03-31T21:29:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88941d5fd78", "title": "Repairing a dead Kenwood TS-850S", "url": "https://ka7oei.blogspot.com/2024/02/repairing-dead-kenwood-ts-850s.html", "published_at": "2024-02-24T18:10:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88942a8c5e1", "title": "Reducing RFI (Radio Frequency Interference) for a POE (Power Over Ethernet) camera or wireless access point", "url": "https://ka7oei.blogspot.com/2024/01/reducing-rfi-radio-frequency.html", "published_at": "2024-01-14T22:55:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8894326e109", "title": "Remote (POTA) operation from the Conger Mountain BLM Wilderness Area (K-6085)", "url": "https://ka7oei.blogspot.com/2023/12/remote-pota-operation-from-conger.html", "published_at": "2023-12-27T07:03:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88943aa1c7e", "title": "\"TDOA\" direction finder systems - Part 2 - Determining signal bearing from switching antennas in software.", "url": "https://ka7oei.blogspot.com/2023/12/tdoa-direction-finder-systems-part-2.html", "published_at": "2023-12-13T22:02:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c889444ac020", "title": "A simple VHF notch cavity from scraps of (large) Heliax", "url": "https://ka7oei.blogspot.com/2023/11/a-simple-vhf-notch-cavity-from-scraps.html", "published_at": "2023-11-23T01:55:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8894481f137", "title": "Observations, analysis and field use of the JPC-7 portable \"dipole\" antenna", "url": "https://ka7oei.blogspot.com/2023/11/observations-and-analysis-and-field-use.html", "published_at": "2023-11-03T16:47:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88944ec5c7e", "title": "Multi-band transmitter and monitoring system for Eclipse monitoring (Part 1)", "url": "https://ka7oei.blogspot.com/2023/10/multi-band-transmitter-and-monitoring.html", "published_at": "2023-10-20T17:25:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88945d8dab2", "title": "Remote (POTA) operation from Canyonlands National Park (K-0010)", "url": "https://ka7oei.blogspot.com/2023/10/remote-pota-operation-from-canyonlands.html", "published_at": "2023-10-18T00:30:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c88945f0be14", "title": "Resurrecting my FE-5680A Rubidium frequency reference", "url": "https://ka7oei.blogspot.com/2023/10/resurrecting-my-fe-5680a-rubidium.html", "published_at": "2023-10-02T01:35:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8894680c917", "title": "Measuring signal dynamics of the RX-888 (Mk2)", "url": "https://ka7oei.blogspot.com/2023/09/measuring-signal-dynamics-of-rx-888-mk2.html", "published_at": "2023-09-04T23:08:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c889471e7ed7", "title": "Improving the thermal management of the RX-888 (Mk2)", "url": "https://ka7oei.blogspot.com/2023/08/improving-thermal-management-of-rx-888.html", "published_at": "2023-08-30T01:46:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c8894814026b", "title": "A solid state replacement for an old radio's \"vibrator\" (Wards Airline 62-345)", "url": "https://ka7oei.blogspot.com/2023/07/a-solid-state-replacement-for-old.html", "published_at": "2023-07-31T23:35:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c889482081bc", "title": "Modifying an \"O2-Cool\" battery fan to (also) run from 12 volts", "url": "https://ka7oei.blogspot.com/2023/07/modifying-o2-cool-battery-fan-to-also.html", "published_at": "2023-07-19T07:05:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c889489d62eb", "title": "It *is* possible to have an RF-quiet home PV (solar) electric system!", "url": "https://ka7oei.blogspot.com/2020/08/it-is-possible-to-have-rf-quiet-home-pv.html", "published_at": "2023-06-30T15:55:00+00:00" }, { "id": "01a0bb55-b020-736a-944d-c889497c34b1", "title": "Characterizing spurious (Harmonic) responses of the SDRPlay RSP1a (and other models)", "url": "https://ka7oei.blogspot.com/2023/05/characterizing-spurious-harmonic.html", "published_at": "2023-05-21T15:21:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c568b3cc", "title": "Exploring the \"1-930MHz 2W RF Broadband Power Amplifier Module for FM Radio HF VHF Transmission\" found on EvilBay", "url": "https://ka7oei.blogspot.com/2023/04/exploring-1-930mhz-2w-rf-broadband.html", "published_at": "2023-04-04T14:49:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c5b0f409", "title": "Injection locking cheap crystal \"can\" oscillators to an external source", "url": "https://ka7oei.blogspot.com/2023/03/injection-locking-cheap-crystal-can.html", "published_at": "2023-03-04T21:53:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c62ad235", "title": "\"CQ CQ - Calling all dielectric welders!\" (Or, those strange curvy things seen on a 10 meter waterfall)", "url": "https://ka7oei.blogspot.com/2023/02/cq-cq-calling-all-dielectric-welders-or.html", "published_at": "2023-02-11T03:09:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c6819c37", "title": "A 2 meter band-pass cavity using surplus \"Heliax\"", "url": "https://ka7oei.blogspot.com/2023/01/a-2-meter-band-pass-cavity-using.html", "published_at": "2023-01-31T03:35:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c687830c", "title": "Exploring the NDK 9200Q7 10 MHz OCXO (Oven-controlled Crystal Oscillator)", "url": "https://ka7oei.blogspot.com/2022/12/exploring-ndk-9200q7-10-mhz-ocxo-oven.html", "published_at": "2022-12-29T00:22:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c6f37134", "title": "An LCD Retrofit and color display for the Schlumberger SI 4031 Communications Test Set", "url": "https://ka7oei.blogspot.com/2022/12/an-lcd-retrofit-and-color-display-for.html", "published_at": "2022-12-02T21:40:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c7b11346", "title": "Using an inexpensive PT2399 music reverb/effects board as an audio delay (for repeater use)", "url": "https://ka7oei.blogspot.com/2022/11/using-inexpensive-pt2399-music.html", "published_at": "2022-11-16T19:04:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c85af1ac", "title": "An ultrasonic superheterodyne receive converter (e.g. \"Bat Listener\")", "url": "https://ka7oei.blogspot.com/2022/10/an-superheterodyne-ultrasonic-receive.html", "published_at": "2022-10-31T03:45:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c8b4fa87", "title": "Using an ATX computer power supply to run KiwiSDRs - and as a general purpose 5 and 12 volt supply", "url": "https://ka7oei.blogspot.com/2022/09/using-atx-computer-power-supply-to-run.html", "published_at": "2022-09-28T03:34:00+00:00" }, { "id": "01a0bb5b-3bb7-73ad-badb-35d8c95887a1", "title": "Making a \"Word Metronome\" for pacing of speech", "url": "https://ka7oei.blogspot.com/2022/08/making-word-metronome-for-pacing-of.html", "published_at": "2022-08-31T01:32:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9659f57d", "title": "Improving my ultrasonic sniffer for finding power line arcing by using MEMs microphones", "url": "https://ka7oei.blogspot.com/2022/07/blog-post.html", "published_at": "2022-08-01T04:18:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec96b5315d", "title": "The use case for a blinking infrared LED", "url": "https://ka7oei.blogspot.com/2022/06/the-use-case-for-blinking-infrared-led.html", "published_at": "2022-06-29T14:27:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec97221211", "title": "Fixing a TS-570G (The tuner couldn't find a match, timing out...)", "url": "https://ka7oei.blogspot.com/2022/05/fixing-ts-570g.html", "published_at": "2022-05-29T02:25:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec97483d2c", "title": "Implementing the (functional equivalent of a) Hilbert Transform with minimal overhead", "url": "https://ka7oei.blogspot.com/2022/04/implementing-functional-equivalent-of.html", "published_at": "2022-05-01T05:07:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec98389b95", "title": "High power Tayloe (a.k.a. Wheatstone) absorptive bridge for VSWR indication and rig protection.", "url": "https://ka7oei.blogspot.com/2022/02/high-power-tayloe-aka-wheatstone.html", "published_at": "2022-02-28T05:35:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec987b6274", "title": "Testing the FlyDog SDR (KiwiSDR \"clone\")", "url": "https://ka7oei.blogspot.com/2022/01/testing-flydog-sdr-kiwisdr-clone.html", "published_at": "2022-01-22T14:47:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec99220205", "title": "The case of the Clicky Carrier - Likely high-frequency trading (that can sometimes clobber the upper part of 20 meters)", "url": "https://ka7oei.blogspot.com/2021/12/the-case-of-clicky-carrier.html", "published_at": "2021-12-03T21:34:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9973bd5e", "title": "Fixing the CAT Systems DL-1000 and AD-1000 repeater audio delay boards", "url": "https://ka7oei.blogspot.com/2021/11/fixing-cat-systems-dl-1000-and-ad-1000.html", "published_at": "2021-11-25T17:47:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec99a57ce0", "title": "RF Quieting a Samlex 150 watt Sine Wave inverter", "url": "https://ka7oei.blogspot.com/2021/10/quieting-samlex-150-watt-sine-wave.html", "published_at": "2021-10-30T02:03:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec99e6bd23", "title": "Pink bits of rubber causing a blinking light... (Problems with Jeep Rubicon sway bar disconnect mechanism)", "url": "https://ka7oei.blogspot.com/2021/09/pink-bits-of-rubber-causing-blinking.html", "published_at": "2021-09-29T02:47:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9a6ee2c4", "title": "A \"portable\", high power, high-sensitivity remote repeater covering deep river gorges in Utah", "url": "https://ka7oei.blogspot.com/2021/06/a-high-power-high-sensitivity-remote.html", "published_at": "2021-06-30T20:31:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9b4c276b", "title": "Characterizing the RTL-SDR Blog (Version 3) for HF reception using the \"direct\" input.", "url": "https://ka7oei.blogspot.com/2021/05/characterizing-rtl-sdr-block-version-3.html", "published_at": "2021-05-22T22:57:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9b7748e1", "title": "Repair of a (lightning struck?) Yaesu FT-1000 MP Mark V", "url": "https://ka7oei.blogspot.com/2021/04/repair-of-lightning-struck-yaesu-ft.html", "published_at": "2021-05-01T05:49:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9bf6a95f", "title": "Using the QRP Labs \"SoftRock\" as a possible crystal replacement in \"rock bound\" VHF and UHF radios", "url": "https://ka7oei.blogspot.com/2018/10/using-qrp-labs-softrock-as-crystal.html", "published_at": "2021-03-24T18:08:00+00:00" }, { "id": "01a0bb5b-3bb8-72ea-b0a4-a6ec9cd435cd", "title": "The appearance of the \"Chinese Woodpecker\" on the HF bands", "url": "https://ka7oei.blogspot.com/2021/02/the-appearance-of-chinese-woodpecker-on.html", "published_at": "2021-02-14T20:29:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58410c546", "title": "RFI (Radio Frequency Interference) sleuthing with the TinySA - Part 1: The gear", "url": "https://ka7oei.blogspot.com/2021/02/rfi-radio-frequency-interference.html", "published_at": "2021-02-08T04:52:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58461d873", "title": "Using surplus GE Mastr II and Exec II transmitters as amateur radio beacon transmitters", "url": "https://ka7oei.blogspot.com/2020/02/using-surplus-ge-mastr-ii-and-exec-ii.html", "published_at": "2021-01-28T23:11:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58545ca38", "title": "Locking the Icom IC-910H to an external 10 MHz (GPS) reference", "url": "https://ka7oei.blogspot.com/2020/12/locking-icom-ic-910h-to-external-10-mhz.html", "published_at": "2020-12-20T16:22:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b585eec836", "title": "Intruder at the top of the 20 meter amateur band?", "url": "https://ka7oei.blogspot.com/2020/12/intruder-at-top-of-20-meter-amateur-band.html", "published_at": "2020-12-15T16:10:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b5865a6190", "title": "Interesting signals on the 20 meter band: Probable Radio Habana Cuba transmitter malfunction - not jamming", "url": "https://ka7oei.blogspot.com/2020/11/interesting-signals-on-20-meter-band.html", "published_at": "2020-11-17T15:27:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58704a91a", "title": "A high-current DC (and AC) noise filter for UPS or RV use", "url": "https://ka7oei.blogspot.com/2020/11/a-high-current-dc-noise-filter-for-ups.html", "published_at": "2020-11-14T16:59:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b587571e1c", "title": "Using the jt9 executable to receive FST4W signals", "url": "https://ka7oei.blogspot.com/2020/10/using-jt9-executable-to-receive-fst4w.html", "published_at": "2020-10-22T16:23:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b5876a83db", "title": "Revisiting the \"Limited Attenuation High Pass\" filter - again.", "url": "https://ka7oei.blogspot.com/2020/08/revisiting-limited-attenuation-high.html", "published_at": "2020-09-27T03:19:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b588246100", "title": "Comparing the \"KiwiSDR\" and the \"RaspberrySDR\" software-defined receivers", "url": "https://ka7oei.blogspot.com/2020/09/comparing-kiwisdr-and-raspberrysdr.html", "published_at": "2020-09-16T01:06:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b5891a44ad", "title": "An automatic transfer relay for UPS/Critical loads, for the ham shack, generator backup, and home", "url": "https://ka7oei.blogspot.com/2020/07/an-automatic-transfer-relay-for.html", "published_at": "2020-07-08T01:10:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b589b85ece", "title": "What the heck happened to this Sense power monitoring module?", "url": "https://ka7oei.blogspot.com/2020/07/what-heck-happened-to-this-sense-power.html", "published_at": "2020-07-03T05:15:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b589e32f84", "title": "An ESP8266-based Temperature, Humidity and Line Voltage monitor", "url": "https://ka7oei.blogspot.com/2020/06/an-esp8266-based-temperature-humidity.html", "published_at": "2020-06-07T16:33:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b589f65b66", "title": "A quick look at the QB-300 RF amplifier", "url": "https://ka7oei.blogspot.com/2020/05/a-quick-look-at-qb-300-amplifier.html", "published_at": "2020-05-17T18:42:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58a3a3ea5", "title": "A \"curiously sharp\" 40 meter band-pass filter to reduce 41 meter SWBC overload.", "url": "https://ka7oei.blogspot.com/2020/05/a-curiously-sharp-40-meter-band-pass.html", "published_at": "2020-05-10T03:57:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58ac40c97", "title": "About the WSPRDaemon noise graphs - and repurposing for use in monitoring WWV(B) signal levels over time.", "url": "https://ka7oei.blogspot.com/2020/04/about-wsprdaemon-noise-graphs-and.html", "published_at": "2020-04-25T18:53:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58b57c355", "title": "Setting/calibrating signal and noise levels for signal/noise level monitoring using the \"wsprdaemon\" script", "url": "https://ka7oei.blogspot.com/2020/03/settingcalibrating-signal-and-noise.html", "published_at": "2020-03-28T17:55:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58c5656cb", "title": "Improving the stability and performance of the FiFi SDR receiver", "url": "https://ka7oei.blogspot.com/2020/01/improving-stability-and-performance-of.html", "published_at": "2020-01-16T16:37:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58cd91947", "title": "Using TV (F-connector) 75 ohm splitters and taps in 50 ohm systems on the amateur HF, VHF and UHF bands", "url": "https://ka7oei.blogspot.com/2019/12/using-tv-type-75-ohm-splitters-and-taps.html", "published_at": "2019-12-26T22:36:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58dc681b4", "title": "Automatically re-connecting low-voltage cut-outs for 12 and 24 volt lead acid battery systems", "url": "https://ka7oei.blogspot.com/2019/12/automatically-re-connecting-low-voltage.html", "published_at": "2019-12-07T23:09:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58e4b47f9", "title": "Homebrew construction of 2 and 4 port splitters/combiners for the LF-MF-HF(30 kHz-30 MHz) frequency range.", "url": "https://ka7oei.blogspot.com/2019/11/homebrew-construction-of-2-and-4-port.html", "published_at": "2019-11-17T17:00:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58e5e61b3", "title": "Characterizing the Mini-Circuits ZFSC-4-3, ZFDC-20-3, ZFSC-4-1-BNC+ and ZFSC-2-1+ well below their designed frequency range", "url": "https://ka7oei.blogspot.com/2019/11/characterizing-mini-circuits-zfsc-4-3.html", "published_at": "2019-11-06T19:32:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58eaba11b", "title": "Shunt regulation of series-connected lead-acid batteries to equalize the voltage", "url": "https://ka7oei.blogspot.com/2019/10/shunt-regulation-of-series-connected.html", "published_at": "2019-10-27T18:00:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58f789c5c", "title": "A LiIon Pack for the Yaesu FT-530 - and (possibly) other older handie-talkies (HTs).", "url": "https://ka7oei.blogspot.com/2019/09/a-liion-pack-for-yaesu-ft-530-eg.html", "published_at": "2019-10-01T02:50:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b58f96bf7a", "title": "Revisiting the limited attenuation high-pass filter for the KiwiSDR (or SDRPlay, RTL-SDR Dongle, Fun Cube, or other SDR receivers)", "url": "https://ka7oei.blogspot.com/2019/08/revisiting-limited-attenuation-high.html", "published_at": "2019-08-14T14:38:00+00:00" }, { "id": "01a0bb63-4dc0-7284-9e72-89b5906ba81e", "title": "Using the same feedline for HF/6 meters and 2 meters/70cm (with a diplexer)", "url": "https://ka7oei.blogspot.com/2019/06/using-same-feedline-for-hf6-meters-and.html", "published_at": "2019-06-09T19:11:00+00:00" } ] posts Claim your blog
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ka7oei.blogspot.com

2026

The Comcraft CTR-144 FM transceiver - A "multi-mode" solid state 2 Meter transceiver from the early 1970s.original ↗
16 Sept 2026
The Morrow CM-1 receiver - A relic of the cold war's effect on amateur radiooriginal ↗
15 Aug 2026
A new push-pull switch/potentiometer for the Heathkit HM-102 VSWR/Wattmeteroriginal ↗
28 Jul 2026
Making LED headlights RF-quietoriginal ↗
12 Jul 2026
Replacing the relays in the Yaesu FT-480R (FT-280)original ↗
27 May 2026
A (simple) WWVB loop amplifier for radio-controlled clocksoriginal ↗
12 Apr 2026
Repairing a ("smoked") MFJ-998 1.5kW automatic antenna tuneroriginal ↗
18 Mar 2026
Modifying the MFJ-5008 parabolic ultrasonic receiver for better sensitivity and wider frequency responseoriginal ↗
4 Mar 2026
Impedance matching (auto) transformer and common-mode choke for the JPC-7 dipole and other electrically-short (loaded) dipoles and verticalsoriginal ↗
26 Feb 2026
How I prevented QRM to HF reception from my solar charger and AC inverter at Quartzfestoriginal ↗
23 Jan 2026

2025

Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 3 (of 3)original ↗
25 Dec 2025
Adding ALC and overdrive protection to the MFJ ALS-500M "500 watt" amplifieroriginal ↗
28 Nov 2025
A "sharp" 160 meter receive-only band-pass filteroriginal ↗
26 Oct 2025
DXing distant SolarEdge PV optimizer modules (or long-distance propagation of PV system QRM)original ↗
10 Sept 2025
Exploring the Ameco PCL-P Nuvistor cascode preamp/preselectororiginal ↗
24 Aug 2025
Reducing RF susceptibility for the HamGadgets "Ultra Pico Keyer" - and mimizing RF issues on portable HF stations in generaloriginal ↗
29 Jul 2025
A 15 (and 10) meter high-pass filter for Field Dayoriginal ↗
13 Jun 2025
The construction of a hybrid ring combiner: Using the same duplexer, feedline and antenna for two repeaters/links/transmittersoriginal ↗
4 Jun 2025
Refurbishing a CIR Astro 200 HF amateur band transceiveroriginal ↗
2 May 2025
Using a PIR to reduce wear and tear on a Nixie clockoriginal ↗
8 Apr 2025
Repairing a NanoVNA "V2" with nonsensical readings ("Blown up" input)original ↗
14 Mar 2025
Ali Express "SDR TX/RX Switch" - A design NOT well thought out...original ↗
16 Feb 2025
A short-term capacitor-based "UPS" for mini (NUC-type) PCsoriginal ↗
27 Jan 2025

2024

Charging LiFePO4 batteries from a vehicular electrical system - the problems and a solution.original ↗
28 Dec 2024
Frequency response of the RX-888 SDR at the high and low ends (Above 30 MHz, below 1.5 MHz)original ↗
4 Dec 2024
The "Universal TCXO" - better stability for the Kenwood TS-590, TS-570, TS-480 (and other radios) using the QRP Labs ProgRock 2original ↗
25 Nov 2024
Hiking and POTA (Parks On the Air) operation from Arches National Park (US-0004)original ↗
1 Nov 2024
Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 2 (of 3)original ↗
1 Oct 2024
Neon bar-graph VSWR/Power meter using the ИН-13 (a.k.a "IN-13") "Nixie" - Part 1 (of 3)original ↗
28 Aug 2024
Rewinding the stainless steel coils with silver-plated copper wire on the JPC-7 and JPC-12 antennasoriginal ↗
31 Jul 2024
Reducing QRM (interference) from a Renogy 200 watt (or any other!) portable solar panel systemoriginal ↗
1 Jul 2024
Observations, analysis and modifications of the JPC-12 vertical antennaoriginal ↗
29 May 2024
Repairing a dead RX-888 (no A/D converter clocking)original ↗
15 May 2024
Analysis of interference from a SolarEdge PV (solar) electric system.original ↗
1 May 2024
Using an external clock with the RX-888 (Mk2)original ↗
31 Mar 2024
Repairing a dead Kenwood TS-850Soriginal ↗
24 Feb 2024
Reducing RFI (Radio Frequency Interference) for a POE (Power Over Ethernet) camera or wireless access pointoriginal ↗
14 Jan 2024

2023

Remote (POTA) operation from the Conger Mountain BLM Wilderness Area (K-6085)original ↗
27 Dec 2023
"TDOA" direction finder systems - Part 2 - Determining signal bearing from switching antennas in software.original ↗
13 Dec 2023
A simple VHF notch cavity from scraps of (large) Heliaxoriginal ↗
23 Nov 2023
Observations, analysis and field use of the JPC-7 portable "dipole" antennaoriginal ↗
3 Nov 2023
Multi-band transmitter and monitoring system for Eclipse monitoring (Part 1)original ↗
20 Oct 2023
Remote (POTA) operation from Canyonlands National Park (K-0010)original ↗
18 Oct 2023
Resurrecting my FE-5680A Rubidium frequency referenceoriginal ↗
2 Oct 2023
Measuring signal dynamics of the RX-888 (Mk2)original ↗
4 Sept 2023
Improving the thermal management of the RX-888 (Mk2)original ↗
30 Aug 2023
A solid state replacement for an old radio's "vibrator" (Wards Airline 62-345)original ↗
31 Jul 2023
Modifying an "O2-Cool" battery fan to (also) run from 12 voltsoriginal ↗
19 Jul 2023
It *is* possible to have an RF-quiet home PV (solar) electric system!original ↗
30 Jun 2023
Characterizing spurious (Harmonic) responses of the SDRPlay RSP1a (and other models)original ↗
21 May 2023
Exploring the "1-930MHz 2W RF Broadband Power Amplifier Module for FM Radio HF VHF Transmission" found on EvilBayoriginal ↗
4 Apr 2023
Injection locking cheap crystal "can" oscillators to an external sourceoriginal ↗
4 Mar 2023
"CQ CQ - Calling all dielectric welders!" (Or, those strange curvy things seen on a 10 meter waterfall)original ↗
11 Feb 2023
A 2 meter band-pass cavity using surplus "Heliax"original ↗
31 Jan 2023

2022

Exploring the NDK 9200Q7 10 MHz OCXO (Oven-controlled Crystal Oscillator)original ↗
29 Dec 2022
An LCD Retrofit and color display for the Schlumberger SI 4031 Communications Test Setoriginal ↗
2 Dec 2022
Using an inexpensive PT2399 music reverb/effects board as an audio delay (for repeater use)original ↗
16 Nov 2022
An ultrasonic superheterodyne receive converter (e.g. "Bat Listener")original ↗
31 Oct 2022
Using an ATX computer power supply to run KiwiSDRs - and as a general purpose 5 and 12 volt supplyoriginal ↗
28 Sept 2022
Making a "Word Metronome" for pacing of speechoriginal ↗
31 Aug 2022
Improving my ultrasonic sniffer for finding power line arcing by using MEMs microphonesoriginal ↗
1 Aug 2022
The use case for a blinking infrared LEDoriginal ↗
29 Jun 2022
Fixing a TS-570G (The tuner couldn't find a match, timing out...)original ↗
29 May 2022
Implementing the (functional equivalent of a) Hilbert Transform with minimal overheadoriginal ↗
1 May 2022
High power Tayloe (a.k.a. Wheatstone) absorptive bridge for VSWR indication and rig protection.original ↗
28 Feb 2022
Testing the FlyDog SDR (KiwiSDR "clone")original ↗
22 Jan 2022

2021

The case of the Clicky Carrier - Likely high-frequency trading (that can sometimes clobber the upper part of 20 meters)original ↗
3 Dec 2021
Fixing the CAT Systems DL-1000 and AD-1000 repeater audio delay boardsoriginal ↗
25 Nov 2021
RF Quieting a Samlex 150 watt Sine Wave inverteroriginal ↗
30 Oct 2021
Pink bits of rubber causing a blinking light... (Problems with Jeep Rubicon sway bar disconnect mechanism)original ↗
29 Sept 2021
A "portable", high power, high-sensitivity remote repeater covering deep river gorges in Utahoriginal ↗
30 Jun 2021
Characterizing the RTL-SDR Blog (Version 3) for HF reception using the "direct" input.original ↗
22 May 2021
Repair of a (lightning struck?) Yaesu FT-1000 MP Mark Voriginal ↗
1 May 2021
Using the QRP Labs "SoftRock" as a possible crystal replacement in "rock bound" VHF and UHF radiosoriginal ↗
24 Mar 2021
The appearance of the "Chinese Woodpecker" on the HF bandsoriginal ↗
14 Feb 2021
RFI (Radio Frequency Interference) sleuthing with the TinySA - Part 1: The gearoriginal ↗
8 Feb 2021
Using surplus GE Mastr II and Exec II transmitters as amateur radio beacon transmittersoriginal ↗
28 Jan 2021

2020

Locking the Icom IC-910H to an external 10 MHz (GPS) referenceoriginal ↗
20 Dec 2020
Intruder at the top of the 20 meter amateur band?original ↗
15 Dec 2020
Interesting signals on the 20 meter band: Probable Radio Habana Cuba transmitter malfunction - not jammingoriginal ↗
17 Nov 2020
A high-current DC (and AC) noise filter for UPS or RV useoriginal ↗
14 Nov 2020
Using the jt9 executable to receive FST4W signalsoriginal ↗
22 Oct 2020
Revisiting the "Limited Attenuation High Pass" filter - again.original ↗
27 Sept 2020
Comparing the "KiwiSDR" and the "RaspberrySDR" software-defined receiversoriginal ↗
16 Sept 2020
An automatic transfer relay for UPS/Critical loads, for the ham shack, generator backup, and homeoriginal ↗
8 Jul 2020
What the heck happened to this Sense power monitoring module?original ↗
3 Jul 2020
An ESP8266-based Temperature, Humidity and Line Voltage monitororiginal ↗
7 Jun 2020
A quick look at the QB-300 RF amplifieroriginal ↗
17 May 2020
A "curiously sharp" 40 meter band-pass filter to reduce 41 meter SWBC overload.original ↗
10 May 2020
About the WSPRDaemon noise graphs - and repurposing for use in monitoring WWV(B) signal levels over time.original ↗
25 Apr 2020
Setting/calibrating signal and noise levels for signal/noise level monitoring using the "wsprdaemon" scriptoriginal ↗
28 Mar 2020
Improving the stability and performance of the FiFi SDR receiveroriginal ↗
16 Jan 2020

2019

Using TV (F-connector) 75 ohm splitters and taps in 50 ohm systems on the amateur HF, VHF and UHF bandsoriginal ↗
26 Dec 2019
Automatically re-connecting low-voltage cut-outs for 12 and 24 volt lead acid battery systemsoriginal ↗
7 Dec 2019
Homebrew construction of 2 and 4 port splitters/combiners for the LF-MF-HF(30 kHz-30 MHz) frequency range.original ↗
17 Nov 2019
Characterizing the Mini-Circuits ZFSC-4-3, ZFDC-20-3, ZFSC-4-1-BNC+ and ZFSC-2-1+ well below their designed frequency rangeoriginal ↗
6 Nov 2019
Shunt regulation of series-connected lead-acid batteries to equalize the voltageoriginal ↗
27 Oct 2019
A LiIon Pack for the Yaesu FT-530 - and (possibly) other older handie-talkies (HTs).original ↗
1 Oct 2019
Revisiting the limited attenuation high-pass filter for the KiwiSDR (or SDRPlay, RTL-SDR Dongle, Fun Cube, or other SDR receivers)original ↗
14 Aug 2019
Using the same feedline for HF/6 meters and 2 meters/70cm (with a diplexer)original ↗
9 Jun 2019
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