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When Band-Pass/Band-Reject (Bp/Br) duplexers really aren't band-pass!
In the repeater world there is a misconception that just because the duplexer may say "Band Pass, Band Reject" on its label - or even in its 'spec sheet - that it really does offer a proper band-pass...
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Fixing my failed "Kill-A-Watt" meter - and a bit about capacitive dropper...
A few days ago I had the need to measure the load of an appliance, so I dug out my "Kill-A-Watt" power meter. The purpose of this device is to measure not only the load of the appliance in watts, but...
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A 10 MHz OCXO (Oven-controlled Crystal Oscillator)
Figure 1:The 10 MHz OCXO (lower right) in use with my homebrew24 GHz transverter. At 24 GHz, the oven provides excellent frequencystability, suitable for SSB or even digital modes, while providing...
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A (semi)-typical suburban E-field whip receive system for the 630 and 2200...
Even though the general availability of the 630 meter (472-479 kHz) and 2200 meter (135.7-137.8 kHz) bands to U.S. amateurs is a recent phenomenon, I've had interest in these frequency ranges for about...
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An alternative PA (output) transistor for the QRP Labs Ultimate 3S beacon
The QRP Labs Ultimate 3S beacon (kit) is a reasonably-priced, compact and self-contained unit capable of operating on any amateur band from 2200 meters through the U.S. 222 MHz band.Sort of.Actually,...
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Matching the 2 and 6 meter cycloid dipoles
The "Cycloid" dipole - a circularly-polarized antenna capable of (more or less) omnidirectional (toward the horizon) radiation was discussed in previous posts:"A circularly-polarized 'omnidirectional'...
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Containing RF noise from a sine wave UPS
An amateur radio friend of mine (WA7X) has a cabin in the mountains. It is not a particularly "rustic" cabin as it is festooned with radios, antennas, propagation beacons, computers and cameras and...
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KA7OEI now QRV on 630 and 2200 meters
Figure 1:The LF/MF transmit station, configured for 630 meter operation.At the time this picture was taken I had not yet completed the gear andput the various pieces in their boxes, hence the mess of...
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Does the Tesla Powerwall 2 produce RFI (Radio Frequency Interference)?
Figure 1:A typical Powerwall 2 installation.Left to right: Utility meter/original load center fed from an undergroundpower feed, the"new" load center to which the household circuits nowconnect, the...
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A quick fix for a Yaesu FT-757GXII blank display
A couple weeks ago I was contacted by an old friend of mine, having obtained his amateur license in mid-2017, who has a Yaesu FT-775GXII - a synthesized, all-mode HF transceiver from the the mid-late...
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A simple crystal oven/heater that uses no power resistors
There are times where one needs to elevate a component to a consistent temperature to better-maintain its characteristics, the most common being the need to heat a quartz crystal to attain better...
View ArticleUn-Bricking an RTL-SDR Dongle after an EEPROM write
The other day I was using the "rtl_eeprom" utility to change the serial number of an RTL-SDR dongle (they all ship with serial number "00000001") to make it easier to identify it when it is online with...
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Managing signal dynamics on an RTL-SDR receiver
The so-called "RTL-SDR" dongles are devices that have become quite popular owing to their low cost and their ability to cover a wide frequency range - typically from a few hundred kHz to nearly 1GHz,...
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A novel APD-based speech bandwidth optical receiver
In a previous posting I wrote about a novel application of a JFET (Read about that in the article "Gate current in a JFET - The development of a very sensitive, speech-frequency optical receiver" -...
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Better frequency stability for the QRP Labs "ProgRock" synthesizer
The "ProgRock" synthesizer from QRP Labs link is an inexpensive device based on the Si5131 "any frequency" synthesizer that may be used to produce up to three frequencies simultaneously from around 8...
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Managing HF signal dynamics on an RTL-SDR receiver
Note: This article was inadvertently posted for a few days, before it had been finished. This is the "completed" version of that article. The "RTL-SDR":The so-called "RTL-SDR" dongles are devices...
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Pine needle what?
The afflicted tree: The needles are more normal atthe top, but looking rather "thin" farther down.Because of the number of pine cones, the treelooks "browner" in this picture than it reallyis - but it...
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A "floaty thingie" for keeping NiHM cells topped off
A charge-state maintenance device for NiMH cellsPLEASE NOTE: Messing about with batteries/cells can be hazardous: Most cells contain hazardous materials and injury and/or damage can result from...
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A limited attenuation high-pass filter for the KiwiSDR
Figure 1:Inside the "limited attenuation" high pass filter, housed inside a small, die-cast aluminum enclosure two which BNC connectors were mounted.Click on the image for a larger version.One of the...
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Preventing GFCI "trip on RF"
Figure 1:The installed GFCI (and chokes) in theutility room/laundry room.Click on the image for a larger version.Several months ago I had need to rewire an outlet in my kitchen: Rather than having two...
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