single-sideband

3 Articles

SSB In Your Pocket

August 22, 2022 by 66 Comments

In the old days, a shortwave radio was a major desk fixture. These days, you can get truly diminutive radios. However, most of them only have AM capability (that is, no simple way to receive single-sideband or SSB signals)  and — maybe — the ability to pick up FM broadcast.  Small radios also often have no provision for an external antenna which can be crucial for shortwave radios. [Farpoint Farms] shows off the Raddy RF7860 which is a palm-sided radio, but it has the elusive sideband modes and an external antenna port and wire antenna. It even has a rechargeable battery.

Reading the comments, it appears this is a rebadged version of a HanRongDa HRD 747 radio. Of course, there are other smaller radios with sideband reception like the Tecsun PL368, but they aren’t this small.  If you are in the market for a really tiny shortwave radio, this might be the thing for you.

Of course, the question is what you want to listen to on the shortwave bands these days. There are fewer and fewer broadcasters on shortwave, especially those that broadcast to a general audience. However, if there is something you want to hear, pairing this radio with a good portable antenna, would do the job.

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Understanding Modulated RF With [W2AEW]

January 22, 2019 by 10 Comments

There was a time — not long ago — when radio and even wired communications depended solely upon Morse code with OOK (on off keying). Modulating RF signals led to practical commercial radio stations and even modern cell phones. Although there are many ways to modulate an RF carrier with voice AM or amplitude modulation is the oldest method. A recent video from [W2AEW] shows how this works and also how AM can be made more efficient by stripping the carrier and one sideband using SSB or single sideband modulation. You can see the video, below.

As is typical of a [W2AEW] video, there’s more than just theory. An Icom transmitter provides signals in the 40 meter band to demonstrate the real world case. There’s discussion about how to measure peak envelope power (PEP) and comparison to average power and other measurements, as well.

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Classifying Crystals With An SDR Dongle

June 6, 2018 by 4 Comments

When it comes to radio frequency oscillators, crystal controlled is the way to go when you want frequency precision. But not every slab of quartz in a tiny silver case is created equal, so crystals need to be characterized before using them. That’s generally a job for an oscilloscope, but if you’re clever, an SDR dongle can make a dandy crystal checker too.

The back story on [OM0ET]’s little hack is interesting, and one we hope to follow up on. The Slovakian ham is building what looks to be a pretty sophisticated homebrew single-sideband transceiver for the HF bands. Needed for such a rig are good intermediate frequency (IF) filters, which require matched sets of crystals. He wanted a quick and easy way to go through his collection of crystals and get a precise reading of the resonant frequency, so he turned to his cheap little RTL-SDR dongle. Plugged into a PC with SDRSharp running, the dongle’s antenna input is connected to the output of a simple one-transistor crystal oscillator. No schematics are given, but a look at the layout in the video below suggests it’s just a Colpitts oscillator. With the crystal under test plugged in, the oscillator produces a huge spike on the SDRSharp spectrum analyzer display, and [OM0ET] can quickly determine the center frequency. We’d suggest an attenuator to change the clipped plateau into a sharper peak, but other than that it worked like a charm, and he even found a few dud crystals with it.

Fascinated by the electromechanics of quartz crystals? We are too, which is why [Jenny]’s crystal oscillator primer is a good first stop for the curious.

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