Reactivating A Harris RF-130 URT-23 Transmitter

April 8, 2023 by Al Williams 13 Comments

If you enjoy old military hardware, you probably know that Harris made quite a few heavy-duty pieces of radio gear. [K6YIC] picked up a nice example: the Harris RF-130 URT-23. These were frequently used in the Navy and some other service branches to communicate in a variety of modes on HF. The entire set included an exciter, an amplifier, an antenna tuner, and a power supply and, in its usual configuration, can output up to a kilowatt. The transmitter needs some work, and he’s done three videos on the transmitter already. He’s planning on several more, but there’s already a lot to see if you enjoy this older gear. You can see the first three below and you’ll probably want to watch them all, but if you want to jump right to the tear down, you can start with the second video.

You can find the Navy manual for the unit online, dated back to 1975. It’s hard to imagine how much things have changed in 50 years. These radios use light bulbs and weigh almost 500 pounds. [Daniel] had to get his shop wired for 220 V just to run the beast.

It is amusing that some of this old tube equipment had a counter to tell you how many hours the tubes inside had been operating so you could replace them before they were expected to fail. To keep things cool, there’s a very noisy 11,000 RPM fan. The two ceramic final amplifier tubes weigh over 1.5 pounds each!

The third video shows the initial power up. Like computers, if you remember when equipment was like this, today’s lightweight machines seem like toys. Of course, everything works better these days, so we won’t complain. But there’s something about having a big substantial piece of gear with all the requisite knobs, switches, meters, and everything else.

We can’t wait to see the rest of the restoration and to hear this noble radio on the air again. You can tell that [Daniel] loves this kind of gear and you can pick up a lot of tips and lingo watching the videos.

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Info Sought On A Forgotten Cuban Radio

March 21, 2023 by Jenny List 11 Comments

Some of the daily normalities of life in the Cold War seem a little surreal from our perspective in 2023, when nuclear bombers no longer come in to land just down the road and you can head off to Poland or Czechia on a whim. Radio amateurs were one of the few groups of civilians whose activities crossed the geopolitical divide, and even though an operator on the other side from ours couldn’t buy a shiny Japanese radio, their homebrew skills matched anything we could do with our Western soldering irons.

[Bill Meara N2CQR] is particularly interested in one line of Cold War-era Communist homebrew radios, the tube-based Cuban “Islander” and its solid-state “Jaguey” sibling. It’s a homebrew double-sideband transceiver design built using readily-available Soviet TV parts, and though he’s published what he can find, he’s on the lookout for more info about these interesting rigs.

The mechanics of a DSB transceiver are simple enough, in that an oscillator and balanced mixer can serve as both modulator and as direct conversion receiver. The fuzzy black and white photographs give frustratingly little detail, but we’re impressed by the quality of what we can see. We have readers all over the world (including we hope, some in Cuba), so perhaps if you know something about these radios you can give Joe a hand. It’s a design that deserves to be appreciated.

For more epic Cold War hackery on the Communist side, read our colleague [Voja Antonic]’s story of his personal computer odyssey.

Morse Code Clock For Training Hams

March 1, 2023 by Bryan Cockfield 13 Comments

It might seem antiquated, but Morse code still has a number of advantages compared to other modes of communication, especially over radio waves. It’s low bandwidth compared to voice or even text, and can be discerned against background noise even at extremely low signal strengths. Not every regulatory agency requires amateur operators to learn Morse any more, but for those that do it can be a challenge, so [Cristiano Monteiro] built this clock to help get some practice.

The project is based around his favorite microcontroller, the PIC16F1827, and uses a DS1307 to keep track of time. A single RGB LED at the top of the project enclosure flashes the codes for hours in blue and minutes in red at the beginning of every minute, and in between flashes green for each second.

Another design goal of this build was to have it operate with as little power as possible, so with a TP4056 control board, single lithium 18650 battery, and some code optimization, [Cristiano] believes he can get around 60 days of operation between charges.

For a project to help an aspiring radio operator learn Morse, a simple build like this can go a long way. For anyone else looking to build something similar we’d note that the DS1307 has a tendency to drift fairly quickly, and something like a DS3231 or even this similar Morse code clock which uses NTP would go a long way to keeping more accurate time.

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NASA Help Wanted: Ham Radio Operators Please Apply

February 23, 2023 by Al Williams 42 Comments

NASA’s been recruiting citizen scientists lately, and their latest call is looking for help from ham radio operators. They want you to make and report radio contacts during the 2023 and 2024 North American eclipses. From their website:

Communication is possible due to interactions between our Sun and the ionosphere, the ionized region of the Earth’s atmosphere located roughly 80 to 1000 km overhead. The upcoming eclipses (October 14, 2023, and April 8, 2024) provide unique opportunities to study these interactions. As you and other HamSCI members transmit, receive, and record signals across the radio spectrum during the eclipse, you will create valuable data to test computer models of the ionosphere.

The upcoming eclipses are in October of this year and in April 2024, so you have some time to get your station in order. According to NASA, “It will be a fun, friendly event with a competitive element.” So if you like science, space, or contesting, it sounds like you’ll be interested. Right now, the big event is the Solar Eclipse QSO Party. There will also be a signal spotting challenge and some measurements of WWV, CHU, AM broadcast stations, and measurements of the ionosphere height. There will also be some sort of very low-frequency event. Details on many of these events are still pending.

Hams, of course, have a long history of experimenting with space. They routinely bounce signals off the moon. They also let radio signals bounce off the trails of ionized gas behind meteors using special computer programs.

Digital Library Of Amateur Radio And Communications Is A Treasure Trove

February 20, 2023 by Al Williams 24 Comments

Having a big bookshelf of ham radio books and magazines used to be a point of bragging right for hams. These days, you are more likely to just browse the internet for information. But you can still have, virtually, that big shelf of old ham books, thanks to the DLARC — the digital library of Amateur Radio and Communications.

A grant from a private foundation has enable the Internet Archive to scan and index a trove of ham radio publications, including the old Callbooks, 73 Magazine, several ham radio group’s newsletters from around the globe, Radio Craft, and manuals from Icom, Kenwood, Yaesu, and others.

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Making Variable Capacitors By Stretching Aluminium Cans

September 15, 2022 by Lewin Day 33 Comments

Sometimes when you need a component, the best way to get it is by building it yourself. [North Carolina Prepper] did just that, creating his own trombone-style variable capacitor by stretching some aluminium beverage cans.

The requirement was for a 26 pF to 472 pF capactitor, for a radio transmitting from 7 MHz to 30MHz. The concept was to use two beverage cans, one sliding inside the other, as a capacitor, with an insulating material in between.

To achieve this, a cheap exhaust-pipe expanding tool was used to stretch a regular can to the point where it would readily slide over an unmodified can, plus some additional gap to allow for a plastic insulating sheet in between. Annealing the can is important to stop it tearing up, but fundamentally, it’s a straightforward process.

The resulting trombone capacitor can readily be slid in and out to change its capacitance. The build as seen here achieved 33 pF to 690 pF without too much hassle, not far off the specs [North Carolina Prepper] was shooting for.

Radio hams are very creative at building their own equipment, especially when it comes to variable capacitors. Video after the break.

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Ham Radio Hacking: Thinking Inside The Box

August 2, 2022 by Al Williams 19 Comments

There are two ways to deal with improving ham radio receivers, or — for that matter — any sort of receiver. You can filter and modify the radio frequency including the radio’s intermediate frequency, or you can alter the audio frequency output. Historically, RF and IF techniques have been the most valued because rejecting unwanted noise and signals early allows the rest of the radio to focus on the actual signal of interest. However, audio filters are much easier to work with and until recently, DSPs that could handle RF frequencies were expensive and uncommon. However, [watersstanton] shows us how to make what could be the cheapest audio enhancer ever. It is little more than a modified cardboard box, and you can see and hear the result in the video below.

On the one hand, you shouldn’t expect miracles. On the other hand, you probably have box laying around and can try it in the next three minutes so why not give it a go? You can hear a bit of difference when using the box and not using the box.

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