Portable Ham Radio Design Fosters Experiments

June 16, 2018 by Al Williams 4 Comments

[Charlie Morris] has been busy building a portable ham radio rig and documenting his progress in a series of videos. You can see the first one below. There’s four parts (more if you count things like part 4 and part 4a as two parts) so far and it is always interesting to see inside a build like this, where the choices and tradeoffs are explained.

The first part covers the Si5351 VFO and the associated display. There’s very little to the VFO other than off-the-shelf modules including an Arduino. You can also see the portable Morse code key which is actually a micro switch. The second part experiments with audio amplifiers. [Charlie] looked at the NE5534 vs discrete amplifiers. He was shooting for lowest current draw that was usable. Other parts discuss the RF amplifier and the receiver. Despite the VFO, there is quite a bit of non-module parts by the time things start shaping up.

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Homebrew SDR Ham Radio In 9 Parts

June 6, 2018 by Al Williams 31 Comments

It used to be homebrew ham gear meant something simple. A couple of active devices that could send CW. Maybe a receiver with a VFO. But only the most advanced builders could tackle a wide range SSB transceiver. Today, that goal is still not trivial, but it is way easier due to specialty ICs, ready access to high-speed digital signal processing, and advances in software-defined radio techniques. [Charlie Morris] decided to build an SSB rig that incorporated these technologies and he shared the whole process from design to operation in a series of nine videos. You can see the first one below.

The NE612 is a child of the popular NE602 chip, which contains a Gilbert-cell mixer, and an oscillator that makes building a receiver much easier than it has been in the past. The chips are set up as direct conversion receivers and feed a Teensy which does the digital signal processing on the recovered audio.

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Ham Radio On $100 Or Less

May 28, 2018 by Al Williams 63 Comments

There are a lot of reasons to get a ham radio license, and if you are one of those that think ham radio is dead you can probably skip this post. However, if you have been interested, but didn’t want to drop a lot of money on a station, [KE6MT] has got some great advice for you. He says you can have a rewarding time in ham radio for about $100 of spending.

The post is the advice he wished he had been given in 2015 when he got his license. It turns out you can get on the air very inexpensively these days, especially if you aren’t afraid to build gear from kits.

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Raspberry Pi Is Up Up And Away

May 2, 2018 by Al Williams 3 Comments

BACAR — Balloon Carrying Amateur Radio — is just what it sounds like. A high-altitude balloon carries experiments and communicates via amateur radio. [ZR6AIC] decided to fly a payload in a local BACAR experiment. The module would send its GPS position via the APRS network and also send a Morse code beacon every seven minutes. It also sends other data such as temperature, and has an optional camera fitted.

The hardware used was the ubiquitous Raspberry Pi along with an associated daughterboard for transmitting on the 2 meter ham band. An RTL dongle took care of the receive portion and another dongle provided GPS. A DS18B20 temperature sensor provides the temperature data.

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Drink Lots Of Beer To Raise Your Monopole

January 26, 2018 by Jenny List 17 Comments

When we published a piece about an ADS-B antenna using a Coke can as a groundplane, Hackaday reader [2ftg] got in contact with us about something with a bit more… stature.

A monopole groundplane antenna is a single vertical conductor mounted on an insulator and rising up above a conductive groundplane. In radio terms the groundplane is supposed to look as something of a mirror, to provide a reflection of what would come from the other half of a dipole were there to be two conductors. You can use anything conductive as your monopole, a piece of wire, (in radio amateur humour) a piece of wet string, or even beer cans. “Beer cans?” you ask incredulously, expecting this to be another joke. Yes, beer cans, and [2ftg] has been good enough to supply us with a few examples. The first is a 57-foot stack of them welded together in the 1950s for use on the 80 metre band ( we suspect steel cans may have been more common than aluminum back then), the second is a more modest erection for the 2 metre band, and the final one consists of photographs only of an HF version that looks a little wavy and whose cans are a little less beery.

The reporting in the 1950s piece is rather cheesy, but does give a reasonable description of it requiring welding rods as reinforcement. It also gives evidence of the antenna’s effectiveness, showing that it could work the world. Hardly surprising, given that a decent monopole is a decent monopole no matter how many pints of ale you have dispatched in its making.

The Coke can ADSB can be seen in all its glory here, and if all this amateur radio business sounds interesting, here’s an introduction.

Beer cans picture: Visitor7 [CC BY-SA 3.0].

Neural Network Learns SDR Ham Radio

December 16, 2017 by Al Williams 19 Comments

Identifying ham radio signals used to be easy. Beeps were Morse code, voice was AM unless it sounded like Donald Duck in which case it was sideband. But there are dozens of modes in common use now including TV, digital data, digital voice, FM, and more coming on line every day. [Randaller] used CUDA to build a neural network that could interface with an RTL-SDR dongle and can classify the signals it hears. Since it is a neural network, it isn’t so much programmed to do it as it is trained. The proof of concept has training to distinguish FM, SECAM, and tetra. However, you can train it to recognize other modulation schemes if you want to invest the time into it.

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Radio Amateuring Like It’s 1975

December 7, 2017 by Jenny List 33 Comments

It was a tweet from an online friend in the world of amateur radio, featuring a transmitter design published in Sprat, the journal of the G-QRP club for British enthusiasts of low-power radio. The transmitter was very simple, but seriously flawed: keying the power supply line would cause it to exhibit key clicks and frequency instability. It would probably have been far better leaving the oscillator connected full-time and keying the supply to the amplifier, with of course a suitable key click filter.

[M0CVO]'s Tweet that started it all — [M0CVO]’s Tweet that started it all

We’ve all probably made projects that get the job done at the expense of a bit of performance and economy, and from one angle this circuit is a fantastic example of that art. But it’s not the shortcomings of direct PSU keying a small transmitter that has brought it here, but observation instead of what it represents. Perhaps my social group of radio amateurs differs from the masses, but among them the universal lament is that there is nothing new in a simple transistor transmitter that could just as well have been published in 1977 as 2017.

To explain why this represents a problem, it’s worth giving some background. Any radio amateur will tell you that amateur radio is a wonderful and diverse pastime, in fact a multitude of pastimes rolled into one. Working DX? Got you covered. Contesting? UR 599 OM QRZ? Digital modes pushing the envelope of atmospheric propagation? Satellites? SDRs? GHz radio engineering? All these and many more can be yours for a modest fee and an examination pass. There was a time when radio was electronics, to all intents and purposes, and radio amateurs were at the vanguard of technology. And though electronics has moved on from those days of purely analogue communications and now stretches far beyond anything you’d need a licence and a callsign to investigate for yourself, there are still plenty of places in which an amateur can place themselves at the cutting edge. Software defined radio, for instance, or digital data transmission modes. With an inexpensive single board computer and a few components it is now possible to create a software-defined digital radio station with an extremely low power output, that can be copied on the other side of the world. That’s progress, it’s not so long ago that you would have required a lot of dollars and a lot of watts to do that. Continue reading “Radio Amateuring Like It’s 1975” →