The Comforting Blue Glow Of Old Time Radio

When you think of an old radio it’s possible you imagine a wooden-cased tube radio receiver as clustered around by a 1940s family anxious for news from the front, or maybe even a hefty 19-inch rack casing for a “boat anchor” ham radio transmitter. But neither of those are really old radios, for that we must go back another few decades to the first radios. Radio as demonstrated by Giulielmo Marconi didn’t use tubes and it certainly didn’t use transistors, instead it used an induction coil and a spark gap. It’s a subject examined in depth by [The Plasma Channel] and [Blueprint], as they come together to build and test a pair of spark gap transmitters.

This is a collaboration between two YouTube channels, so we’ve put videos from both below the break.They both build simple spark gap transmitters and explain the history behind them, as well as running some tests in RF-shielded locations. The transmitters are fairly crude affairs in that while they both use electronic drives for their induction coils they don’t have the resonant tank circuitry that a typical early-20th-century transmitter would have had to improve its efficiency.

They are at pains to remind the viewer that spark gap transmitters have been illegal for nearly a century due to their wideband interference so this is definitely one of those “Don’t do this at home” projects even if it hasn’t stopped others from trying. But it’s still a fascinating introduction to this forgotten technology, and both videos are definitely worth a watch.

via Radio Hacks – Hackaday https://ift.tt/31Xo385

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A Work of Art That Also Receives AM and SSB

Over the winter, [Michael LeBlanc] thought a good way to spend his time during those long dark nights would be to scratch build his own direct conversion receiver. He was able to find plans for such a project easily enough online, but where’s the fun in following instructions? The final result incorporates what he found online with his own unique tweaks and artistic style.

[Michael] based his receiver on a modified approach to the DC40 created by [Ashhar Farhan], a name likely familiar to readers involved in amatuer radio. He further modified the design by swapping out the audio amplifier for a TDA2003A, and bolted on a digital tuner by way of an Arduino and a Si5351 clock generator. There’s a small OLED to show the current frequency, which is adjusted with a high-quality Bourns EM14 optical encoder so he can surf the airwaves in the comfort and style.

The digital tuner mated to the analog DC40 receiver gives the radio an interesting duality, which [Michael] really embraces with his enclosure design. Obsensibly he wanted to keep the two halves of the system in their own boxes to minimize any interference, but the 3D printed case exaggerates that practical consideration into a fascinating conversation piece.

The analog and digital compartments are askew, and their rotary controls are on opposite sides. The radio looks like it might topple over if it wasn’t for the fact that the whole thing is bolted together, complete with brass inserts for the printed parts. The integrated carry handle at the top somehow manages to make it look vintage and ultra-modern at the same time. Rarely do you see a printed enclosure that’s both meticulously designed inside and aesthetically pleasing externally. [Michael] earned his 3D Printing Merit Badge for sure with this one.

via Radio Hacks – Hackaday https://ift.tt/2xgPQly

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A Two Metre Bridge Across The Atlantic For The First Time

Amateur radio is a pursuit with many facets, some of which hold more attention than others for the hacker. Though there have been radio amateurs for a century it still has boundaries that are being tested, and sometimes they come in surprising places.

A recent first involved something you might consider a done deal, a transatlantic radio contact. On June 16th, for the first time ever a contact was made between the operators [D41CV] and [FG8OJ] at 3867 km across the Atlantic ocean from the Cape Verde Islands to Guadeloupe, on the 2 metre (144 MHz) band. If this means little to you it’s worth explaining that the 2 m band is a VHF band, with a range normally similar to that you’d expect from an FM broadcast station. Nobody has ever done this before, so it’s a significantly big deal.

Before you dismiss this as merely some radio amateur chasing grid squares and thus not particularly impressive, it’s worth talking about both the radio mode used and the unusual atmospheric conditions that were carefully sought for the achievement. The attempt was made to coincide with a prediction of transatlantic tropospheric ducting, and the mode employed was [Joe Taylor K1JT]’s FT8. This is a digital mode designed especially for weak-signal and long-distance work. It is theorised that the propagation was so-called surface ducting, in which the signal travels and is reflected between the surface of the sea and a relatively low-level reflective layer of atmosphere. The contact really pushed the limit of what is possible with radio, and while you wouldn’t use it for a voice conversation, proves that there are new tricks in an old hobby for the hardcore experimenter.

We’ve talked about [K1JT] modes crossing the Atlantic before, but of course not at such a high frequency.

via Radio Hacks – Hackaday http://bit.ly/2Y97Udo

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Hams Gone Wild: Amateur Radio Field Day 2019

Of all the images that amateur radio conjures up, the great outdoors doesn’t usually figure heavily. People seem to think hams sit in a dark room at a desk heavy with radio gear, banging out Morse code into late into the night and heedless of the world outside the window. All of which sort of sounds like hard-core gaming, really.

And while that image certainly applies in a lot of cases, hams do like to get out and about at least once a year. That day is upon us with the 2019 Amateur Radio Field Day. Hams across North America reserve the fourth full weekend of each June to tear themselves out of their shacks and get into the world to set up operations in some kind of public venue, generally a park or other green space. Part cookout, part community outreach, and part slumber party – it lasts all weekend and goes around the clock – hams use field day as a chance to show the general public where amateur radio really shines: real-time worldwide communications under austere conditions.

It’s also a chance to get folks excited about getting their license, with many Field Day locations hosting “Get on the Air” stations so that unlicensed folks can try making a contact under the supervision of a licensed operator. Licensed but underequipped hams also get the chance to spin the knobs on someone else’s gear, and maybe line up that first rig purchase. And there are plenty of opportunities to learn about new modes as well, such as FT8 and WSPR. As an example your scribe is looking for some guidance on getting started with APRS, the automated packet reporting system that’s used for things like high-altitude balloon tracking.

If you have any interest at all in learning how to properly operate radio equipment, you owe it to yourself to track down the nearest Field Day location and stop by. The American Radio Relay League (ARRL) has a ton of Field Day information, from a map to locate the 1500 Field Day sites to rules for the contests that will be run that weekend to guides for setting up and operating an effective Field Day setup. There will be 40,000 hams out there this year, and they’d all be thrilled if you drop by and ask a few questions.

via Radio Hacks – Hackaday http://bit.ly/2MZYtM9

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Panadaptors Didn’t Start With SDRs

The must-have accessory on a modern all-singing, all-dancing amateur radio transceiver is a panadaptor. Inevitably driven by SDR technology, it’s a view of a band in the frequency domain, and it will usually be displayed as a “waterfall” giving a time dimension to see transmissions over a period.

[Bill Meara, N2CQR] reminds us that panadaptors are nothing new, indeed that they date back to the first half of the last century and don’t even need an SDR to work. And to prove it, he’s produced one for part of the 40-metre amateur band.

The principle behind an analogue panadaptor is simple enough, it’s a normal receiver whose local oscillator is given a linear periodic sweep over the desired frequency band and whose output drives the Y axis of an oscilloscope whose X axis is driven by the sweep. In [Bill]’s case the receiver is a BitX homebrew transceiver, and the swept local oscillator is provided by his Foeltech signal generator. A neat touch comes in the ‘scope being synchronised by triggering on a marker frequency at the bottom of the range being swept. He’s created a video showing it in action, which you can see below the break.

There are quite a few routes into making this type of simple spectrum analyser, indeed some of us have tried ti with TV tuners.

via Radio Hacks – Hackaday http://bit.ly/2WxtmvS

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A DIY Step Attenuator, By Gluing Together Two Smaller Ones

In the RF world, attenuators are a useful test and measurement tool. Variable units that can apply different levels of attenuation in discrete steps are even better. [DuWayne] made a 63 dB step attenuator by putting two smaller units in series, with an Arduino Nano in control of them. With a 3D printed enclosure and OLED for feedback, the device is easily adjusted with a single rotary encoder. There was even room to add a micro USB plug for recharging the power supply.

The two smaller digital attenuators [DuWayne] used are essentially breakout boards for the PE4302 digital RF attenuator, and cheaply available from the usual overseas sources. They are capable of up to 31.5 dB of attenuation in 0.5 dB steps, and by using two in series (and controlling them in parallel) [DuWayne] gets a range of up to 63 dB. The design files can be downloaded from a Dropbox share for the project, should you wish to try any of it for yourself.

Are you interested in RF and maybe software defined radio (SDR)? We’ve covered all the stuff you’ll need to get started with an inexpensive RTL-SDR, and sooner or later you may find yourself in need of [Dan Maloney]’s info on cheap and effective dummy loads.

via Radio Hacks – Hackaday http://bit.ly/2MtdEgG

Your Table Is Ready, Courtesy Of HackRF

Have you ever found yourself in a crowded restaurant on a Saturday night, holding onto one of those little gadgets that blinks and vibrates when it’s your turn to be seated? Next time, bust out the HackRF and follow along with [Tony Tiger] as he shows how it can be used to easily fire them off. Of course, there won’t actually be a table ready when you triumphantly show your blinking pager to the staff; but there’s only so much an SDR can do.

Even if you aren’t looking to jump the line at your favorite dining establishment, the video that [Tony] has put together serves as an excellent practical example of using software defined radio (SDR) to examine and ultimately replicate a wireless communications protocol. The same techniques demonstrated here could be applied to any number of devices out in the wild with little to no modification. Granted these “restaurant pagers” aren’t exactly high security devices to begin with, but you’d be horrified surprised how many other devices out there take a similarly cavalier attitude towards security.

[Tony] starts by using inspectrum to examine the Frequency-shift keying (FSK) modulation used by the 467.750 Mhz devices, and from there, uses Universal Radio Hacker to capture the actual binary data being sent over the air. Between studying the transmissions and the information he found online, he was eventually able to piece together the packet structure used by the restaurant’s base station.

Finally, he wrote a Python script which generates packets based on which pager he wants to set off. If he’s feeling particularly mischievous, he can even set them all off at once. The script outputs a binary file which is then loaded into GNU Radio for transmission via the HackRF. [Tony] says he’s not quite ready to release his script yet, but he gives enough information in the video that the intrepid hacker could probably get their own version up and running by the time he gets it posted up to GitHub anyway.

We saw some very similar techniques demonstrated at the recent WOPR Summit security conference, so once you’re done hacking the local restaurants, you can take these same lessons and apply them to the rest of the Internet of Things. If you’re wondering, it’s even easier to eavesdrop on the non-restaurant pagers.

[Thanks to DarkSim905 for the tip.]

via Radio Hacks – Hackaday http://bit.ly/2QIDpbe

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