6

Land line telegraph keys are fitted with a circuit closer switch. Radio telegraph keys were not but many radio operators used land line keys because they were so readily available. This includes the rather ubiquitous J-38 about which more will be found below. The arcing that occurred at the key contacts of the early spark radios caused radio stations to ...


6

In modern, medium- to high-end equipment, chances of dry solder joints are slim to none, especially in radio equipment, where your solder process needs to be especially safe against this kind of failure to not inadvertedly add parasitic capacitance. I'd agree, electrolyte capacitors are a prime aging suspect. They've gotten better, so in most cases, I ...


3

You say you are "not supposed to build with a kit". Who has set this limitation? This is beginning to sound like a homework assignment. Are you actually expected to design and build a radio receiver and transmitter without looking at other people's prior work? And on top of this, you say in another question that you do not have an amateur radio licence, ...


3

There are standard connectors for microphones, speakers, and headsets, but unfortunately the pinout diagram (schematic) changes very frequently. There is no guarantee that a headset with a 3.5mm TRRS plug that works with one radio will work with a radio from a different manufacturer, or even a different model radio of the same manufacturer. G4WPW's site ...


2

First Steps in Satellites As with trying anything new, it’s best to take small steps as you learn. Here’s a simple exercise to help you get started: listening for the AO-91 FM satellite. Go to AMSAT or N2YO.com, or download one of the satellite tracking apps, and get the latest pass information on the FM satellite AO-91 (also known as Fox-1B). AO-91 has a ...


2

there's at least one you can listen to online: Qatar-OSCAR 100


1

Not only the antenna. It would also include the antenna, the tuned LC circuits, and how tightly the antenna was coupled to the latter. Spark transmitters produced a damped wave. This edited graph from Wikipedia shows one with desirable longer duration. The longer the system "rang", the higher the average power --which is what the decremeter measured-- and ...


1

Capacitor Plague Also keep in mind the capacitor plague that afflicted many electronic devices built between 1999 and 2007. Details on Wikipedia. Short summary abstracted from the Wikipedia article: A higher-than-expected failure rate of non-solid aluminum electrolytic capacitors, between 1999 and 2007, especially those from some Taiwanese manufacturers,...


1

Assuming you want to build from a kit, the simplest kits will be those that use a minimum number of components, avoid having to wind coils, and have only through-hole component mounts. On that basis, and from my own recent experience building one, I'd recommend a Cricket (QRP CW transceiver, includes a built-in key). The Cricket series (they've been ...


1

To directly answer your question, the exact-replacement material would be open-celled polyurethane foam with a density of about 2.0 lb/ft^3 (30 kg/m^3). This can be found at just about any foam outlet store. Alternatives: It does not have to be polyurethane but I have found polyurethane to be far more durable than other foams. The density can be ...


1

Welcome to amateur radio! We hope that our hobby will form the basis for a long and enjoyable career in electronics. One of the most important factors when building your first radio is support, whether you are building from a kit or from "scratch." In-person help from someone who has already built your project is the best, of course, while nearby or in-...


1

Since you (based on comments) know your way around electronics and have built radios, building ham equipment should be a walk in the park -- and more or less parallels my own plans (which, due to personal preference, will use vacuum tubes, aka "valves"). What I intend to do is to start with a simple one-tube regenerative receiver. This can be built for any ...


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