Random musings - usually on a technical (nerdy) subject - perhaps related to amateur radio and things found at ka7oei.com and modulatedlight.org
Figure 1: The front panel of the Morrow CM-1 CONELRAD monitor. The meter indicates relative signal strength and below it is the on/off/volume control. The dial - with a pair of "CD" markings, is a smooth-tuning reduction drive - which is also very accurate. Shown here, it's on and tuned to a local station. Click on the image for a larger version. If you were an amateur (Ham) radio operator in the…
Figure 1: The Heathkit HM-102 HF VSWR/Power meter. This meter - often found at swap meets and hamfests for low cost - is still as useful as it was when new - and is easily repaired today, decades after its introduction. Click on the image for a larger version. A few weeks ago I got my hands on a (nother) Heathkit HM-102 VSWR HF Wattmeter/SWR bridge. This device was available from the early 1970s…
TL;DR If you have LED headlights that are causing RF interference, ferrites alone will probably not be enough to completely solve the problem: You will probably need to put the offending switch-mode LED controller in "RF Jail" as described below. While VHF/UHF is the target of the efforts noted below, they should be equally effective at HF. * * * * * We live in a world of RF - and an increasing…
tl:dr: Figure 1: The front panel of my "FT-280R" all-mode 2 meter transceiver including paper labels showing the "new" modes. Click on the image for a larger version. If you have a Yaesu FT-480R that doesn't work, it's probably the relay(s)! * * * * * Back in 1994 I picked up an FT-280R at a local swap meet for a good price - particularly for an all-mode 2 meter transceiver. Except, of course,…
Note: The techniques described below should work - with only minor adaptation - for any "Longwave" time signal used by these radio-controlled (non-GPS) clocks - not only WWVB, but DCF77, MSF, BPC and both JJY signals as well. * * * * * Last year I moved a bunch of SDRs (KiwiSDRs, RTL-SDR) and a bunch of network gear to a new shelf in my shack, but this placed them much closer to the wall on which…
Figure 1: The (repaired) MFJ-998 front, now working, sitting atop my Heathkit SA-2060 manual tuner and underneath my homebrew neon bar-graph VSWR/Power meter. Click on the image for a larger version. To inspect or not inspect When I buy some types of ham gear second-hand, I'll treat it like as I would if I were to buy used Heathkit gear that had been put together by someone with "average" (or…
Figure 1: Front view MFJ-5008 parabolic dish with integrated microphone and receiver (located on the back side). Click on the image for a larger version The MFJ-5008 Parabolic Ultrasonic receiver Note: Since the MFJ-5008 is no longer being sold it can be found only on the "used" market. A future posting in this blog will (hopefully) show how to construct a similar unit using readily-available kits…
Figure 1: The JPC-7 loaded dipole out in the wild! Click on the image for a larger version. Loading coils and "electrically-short" antennas It is well-known that you can make a "short" wire (e.g. one that is significantly shorter than 1/4 wavelength at the operating frequency) resonant by putting in series with it a coil. There is no "magic" in this as the inductance of the coil, appropriately…
Figure 1: White board from Quartzfest! Click on the image for a larger version As it happens, I found myself at QuartzFest in Arizona in the latter half of January, 2026 where we set up some banners proclaiming the existence of the Northern Utah WebSDR (link) - but I also scribbled on a small white board the words "QRM-Free Solar is possible - Ask How! ". Between the SDR, this message and the…
Figure 1: Power/VSWR meter using ИН-13 neon bar-graph indicators. This was taken prior to installing the dark plastic to improve contrast Click on the image for a larger version In Part 1 (link) I talked a bit about the origination of the design - and how the high voltage for the Neon tubes were generated and how the tubes would be driven along with the "Tandem" power detector using the AD8307…
Figure 1: The ALS-500M front panel. Because this this unit is equipped with the 10 meter low-pass filter, the "AUX" position on the front panel switch is used to select 10/12 meters. Click on the image for a larger version. The MFJ ALS-500M is a (nominally) 500 watt amplifier that was produced by MFJ, capable of covering from 160 meters through 15 meters - and 12/10 meters if so-equipped. If you…
Why the filter? Several years ago I needed a "sharp" 160 Meter band-pass filter - one that would pass 160 Meters with little attenuation, but effectively block top-end signals on the AM broadcast band. Nowadays, the AM (mediumwave) broadcast band goes up to 1700 kHz - but there are relatively few signals in the "new" portion (1610-1700) - yet Murphy's law would dictate that one of those stations…
From how far away can you hear the spurious emissions from a known-noisy PV system? Quite a racket! Figure 1: The spectrum of a SolarEdge PV system from several meters away across the 6-8 MHz range showing "spurs" (clumps of low-level carriers) at 200 kHz intervals and other places. In the above plot the true nature of the individual peak - the fact that each contain many carriers - is not…
"And now, for something completely different!" This past January - at Quartzfest - there was a table covered with "junque" and taped to it was sign with the word "FREE" on it. That's how I ended up with this box. Figure 1: The front panel of the Ameco PCL-P preamp. The left-hand control tunes the front end of the preamp while the right-hand control selects the "band". The in/out switch is on the…
Note: While this article describes a modification of the Pico Keyer to reduce RF susceptibility, it also talks about general methods to minimize/reduce RFI-related issues for both portable and "base" stations: This specific topic is covered near the end of this blog entry. POTA operation Over the past several years I've done a bit of POTA (Parks On The Air) operating, racking up "about" 1000…
QRM from a transmitter to receivers on lower bands [Go to the end of this article for an "After-Field-Day follow-up" about this filter] A friend of mine belongs to a club in a town north of me and he was describing an issue that they've been having for the past several years during ARRL Field Day: A station on an upper band (e.g. 15 or 10 meters) degrading reception on 20 or even 40 meters when…
Two transmitters, one antenna There are occasions when it is desirable to combine two transmitters - and receivers - onto a single antenna - perhaps at a busy repeater site where more than one link or repeater is required. The most obvious answer to this would be to have a separate antenna - and duplexer - for each of the links - but there are potential problems with this: Antennas are expensive…
The Astro 200 The CIR Industries Astro 200 is a compact, synthesized 100 watt HF transceiver from the mid-late 1970s that covers the 80, 40, 20, 15 and 10 meter bands. Intended for both home and mobile use, it is quite small - 9.75" wide, 12.5" deep and 3" tall (24.8 x 31.8 x 7.6cm) - including the rear heat sink. Back in 1977 - when this unit was made - it seems to have cost around $995 for the…
"Does a lit-up Nixie tube in a forest wear out even if there's no-one to see it?" Figure 1: The "Black'n'wood" Nixie Clock (blue back-light turned on) with the PIR (Passive InfraRed) sensor to the right. With no detected movement in the room, the high voltage supply turns off, reducing wear on the tubes. Click on the image for a larger version. This millenia-old riddle has a simple answer: Yes.…
Figure 1: The SAA-2N, a variant of the Version 2. As noted in the text I chose this version as it had N connectors and was suited for my specific needs and has served well for several years. Click on the image for a larger version. The NanoVNA has become a ubiquitous device for the RF toolbox: For less than US$200 you can get a device that is reasonably capable, accurate and covers a usefully-wide…
Figure 1: Front panel of the SDR TX/RX antenna switch showing the the 3.5mm audio connectors and the red/green RX/TX LED - which have been swapped to be in their proper location. Click on the image for a larger version. IMPORTANT: If you have one of these devices, DO NOT connect it to your transceiver and second receiver (SDR) UNTIL you have read and understood the issues described here. Failure…
The problem Figure 1: A "Beelink" small form-factor PC. This unit sports a Ryzen processor and runs from an external 19 volt supply. Click on the image for a larger version. Very small computers (so-called "NUCs" - a term that we'll use generically throughout) of recent manufacture are energy efficient and are increasingly used in lieu of full-size desk top PCs. Many of these use external power…
Figure 1: The Renogy RNG-DCC1212-20 - an isolated and current-limited battery charger, intended for use with vehicle electrical systems. Click on the image for a larger version. There are times - usually on a camping or road trip - where I would like to charge my LiFePO4 batteries en-route, from the vehicle. The "need" is largely the result of having one of those coolers with a built in…
Figure 1: The RX-888 Mk2. For information about improving reception below 1.5 MHz, scroll down to the text surrounding Figure 2. The RX-888 Mk 2 (hereafter referred to as the RX-888 or '888) is a versatile device, essentially providing a means by which "all of HF" (0-30 MHz - or even 0-60 MHz) may be sampled and presented to a computer for processing via a multi-gigabit USB3 interface. As it has…
Figure 1: The TS-590G into which the ProgRock was installed. A useful accessory for many amateur transceivers is a TCXO - a device, often offered as an option, that improves the absolute frequency stability and accuracy of the radio. When in current production, the TCXO is available from the manufacturer - and possibly from third parties - but long after the radio has been made, a TCXO may be…