Tecsun DR-920C Review

Posted on May 9, 2023 by Kevin

I’ve had a DR-920 for years, but the internal string connecting the tuning knob to the variable capacitor went off track in a way I couldn’t repair, so I replaced it with a DR-920C. It cost $25.99 from Amazon, but I had enough “points” so there was nothing out of pocket.

Tecsun DR-920C (Amazon product photo)

The DR-920C is very much like its predecessor, the DR-920. The only differences I can find have to do with the power switch and the alarm. The DR-920 had a POWER/SLEEP button and a LIGHT/SNOOZE button (see photo below). On the side was a slide switch to set the alarm to wake to RADIO or BUZZER. The DR-920C has LIGHT and SLEEP buttons and an ON/OFF slide switch on the side, no wake to buzzer.

Time and alarm setting is a bit unusual in that you have to press as many as 3 buttons at the same time. To set the alarm, for example, you must hold down both the AL SET button and the TIME SET buttons while pressing the HOUR or MINUTE button to change the value. I should add that this radio has a 12-hour clock only.

Tecsun DR-920 (photo by author)

The LIGHT button illuminates the display with a dim amber light that stays on for 10 seconds. The radio has a kickstand, a rotatable whip antenna 22 inches long, a 3v power input jack and an earphone jack. It’s a pretty basic radio.

The DR-920C is a rare breed these days, an analog radio with a digital display run by a frequency counter. The radio uses single-conversion superheterodyne technology, one in which the radio frequency signal is mixed with an internally generated signal, producing a 455 kHz “intermediate frequency,” which is then amplified and demodulated to create an audio signal that is amplified and sent to the speakers. The technology has been around a very long time; my first radio back in 1965 was a “superhet.” The inherent problem with this technology, and why today one would see it only on a cheaper shortwave radio, is images. A station is heard not only on its actual frequency, but if the signal is strong an image appears on its frequency +/- 455 kHz (more on that later).

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Sharing the love

Posted on May 6, 2023 by Kevin

I have a lot of radios. Here are two pictures of them.

My Upstairs Radios
My Downstairs Radios

That’s 25 radios, not counting the novelty radios on the top shelf, clock radios, car radios, the shortwave radio in my car, an SDR, a weather radio on the window sill and a couple in boxes. (The observant reader might have noticed two XHDATA D-109 radios; one of those was the recalled one.) Focusing just on unique working shortwave radios, I think the total comes to 28.

The trouble I had coming up with that number is a symptom of the problem, too many radios with which to share the love.

What’s the solution? Some of my radios I couldn’t sell on eBay when I tried last year. I already gave three to a charity yard sale last week. I think that the 4 on the second from the top left shelf belong in the giveaway pile too, plus a Kchibo KK-959 not shown, and the Rysamton YK-M03 on top of the right shelf. That gets me down to 21, but the Tecsun DR-920C arriving next week takes it back up to 22. That’s too many to appreciate.

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Any Given Sunday

Posted on May 5, 2023 by Kevin

The phrase “any given Sunday” comes from American professional football, a game often played on Sundays. It’s short for “on any given Sunday, any NFL team can defeat any other.” It happens due to random events, special conditions, injuries and luck.

The phrase came to mind as I was listening to Radio Exterior de España on my Raddy RF75A radio indoors with just its 13″ whip antenna. It’s a tiny radio, only 3 1/2 tall. It’s not the sharpest knife in the drawer and has limitations imposed by its size and price point. I have several much better shortwave receivers.

Radio Exterior de España on Raddy RF75A

Normally, this radio doesn’t receive shortwave stations this clearly, and certainly not without an external antenna. But the conditions were good, and the signal was exceptional. The radio sounded great.

Last night around 01:30 I tested my new Tecsun DR-920C. I ran a band scan with my PL-660 and tried to find those signals on the DR-920C. I was using an outdoor MLA-30+ antenna. There were a number of stations with poor quality, and not much good; however 2 hours later I tuned through the bands with the DR-920C just using its whip antenna, and I received many more stations, and good quality signals.

That’s the problem with testing radios: results depend on equipment and conditions. That’s why I try to test radios in pairs with the same antenna; that way at least I have a relative measure independent of the signal.

This year we’ve seen an increase in solar activity and generally improving shortwave reception, but there are also geomagnetic storms that wipe out many signals for a day or two. Conditions are variable now

If you have a new radio and you get hardly anything on shortwave, don’t give up. Wait for a different time of day (generally higher frequencies travel better in the daytime and lower at night any time of the year and you get more stations at night) or try a different day, because on any given Sunday…

PS

Nevertheless, some radios are better than others. Here’s my Tecsun PL-660 receiving Radio Exterior de España on the same 17855 kHz frequency, with just my finger as the antenna.

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Tecsun DR-920: In memoriam

Posted on May 3, 2023 by Kevin

This radio goes back quite a few years, and in fact I had two of them: the Tecsun DR-920 and the alternate branded Lextronix E1100. I gave the Tecsun to a friend years ago who had been a ham radio operator and was terminally ill with cancer. [Documentary evidence unearthed shows that the DR-920 is not the one I gave to my friend, but something else. I sold the DR-920 on eBay. Still it reminds me of my friend.] I still have the E1100. Here are both:

Lextronix E1100 shortwave radio
Tecsun DR-920 shortwave radio

The radio is unusual, one of the few of its type, an analog tuned single-conversion superheterodyne radio with a digital frequency counter readout. It combines the best of both worlds: the smooth continuous tuning of an analog with the precise frequency readout of a digital.

I have a sentimental attachment to the radio because of my friend, now long passed, who got its twin, and so I note with sadness today the passing of my Lextronix E1100 radio.

The Lextronix E1100/DR-920 has a tuning wheel that’s connected through dial stringing and pulleys to a varicap on the circuit board. The varicap froze up and the dial stringing sprung. I couldn’t come up with any way to access the pulley mechanism without cutting a dozen wires that I have no hope of ever being able to repair. A photo of the destructive disassembly is included below.

Lextronix E1100 radio circuit boards

I think the best thing will be to replace it with a DR-920C that looks almost identical to the older model. A new one, I hope, will last longer than an antique, and will be just as good a memento.

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Raddy RF75A MW/FM/SW/WB/VHF Receiver Review

Posted on April 27, 2023 by Kevin

Amazon surprised me by delivering my new Raddy RF75A 5 days early. I already knew it was small, but the size is still remarkable.

Raddy RF75A (left), HanRongDa HRD-701 (right), Tecsun PL-330 (rear)

The RF75A is slightly taller than the HanRongDa HRD-701, but much thinner. Here the already compact Tecsun PL-330 is shown in the rear. The RF75A’s actual dimensions are 92 x 53.2 x 26 mm. It’s also appropriate to show the two front radios together, since they both come from the same product lineage and share many concepts and features, such as the same memory systems and Weather alerts. They can be Bluetooth speakers and play MP3 files. The RF75A is also sold under the HanRongDa brand as model HRD-787 and Retekess as TR111.

While on the topic of the HRD-701, I hasten to praise the RF75A for an improved manual over the HRD-701 that calls the tuning knob a “pulley.” While improved, the Raddy manual still needs work where some of the sentences don’t quite make sense. The manual linked is newer in layout than the one that just came with my radio, but the text seems pretty similar. Readers here know that I have been very critical of radio manuals that are confusing, incomplete, incorrect, written in bad English and that omit critical information. The HRD-701 earned that criticism. The RF75A shows some improvement. I give it a B- grade (see Errata section at end).

Unboxing

The box contains:

  • Raddy RF75A radio
  • Hand strap
  • 21-page Operational Guide
  • 12-page APP Instruction Manual
  • Earbuds
  • External wire antenna with clip
  • USB-C data/charging cable
  • Oversized carry bag

Radio-C

What sets the RF75A radio apart from every other one I have owned is the app that not only allows you to control the radio as if you were pressing its buttons, but also adds features and buttons beyond what the base radio provides. The first example of that is the Record function: the radio can store what it is receiving on a MicroSD card, but recording can only be started with the app. The second feature really blew me away: you can press a single button on the app to set the radio’s clock from the phone’s clock. Probably the most useful app feature is direct entry of frequencies. In music play mode the listener can select the song by number.

Not only does the app provide remote control of the radio, but also remote viewing. The user can view the frequency set. It shows the file name of the MP3 file playing and even displays signal strength and S/N ratio, data not shown on the radio’s display.

The app is called “Radio-C” for Android and “Radio-CT” for iPhone. There is also an app for HarmonyOS.

Audio

The tiny 40mm speaker is rated at 3W, and the radio’s volume can be turned up to an uncomfortable level. It’s a good sound for such a small radio, but more suited for popular music than symphonic to my ear. The SOS siren is extremely loud (independent of the volume control). The Bluetooth connected tone is louder than it needs to be.

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WRTH 2023 WebApp

Posted on April 25, 2023 by Kevin

The long-awaited WebApp version of the World Radio Television Handbook is out. You can purchase it online for $24.90 USD or for $10 if you own the print edition.

WRTH WebApp Home sidebar and Map

As I write this today, it is at version 1.0.1, containing a number of fixes for things I complained about (like the missing article on RDS, scrolling problems on the iPhone and poor formatting of the receiver reviews). It looks more polished than it did just a couple of days ago, pointing out an advantage of the WebApp over the book: if something is wrong it can be fixed. [Update: it’s now (July 26, 2023) at version 1.3.2]

The WebApp (website) opens with a left sidebar of features, and a large world map. You can select topics from the sidebar, and if appropriate pick a country from the map (and optionally a list). The mouse scroll wheel can zoom the map so that individual countries can be seen and selected by double-clicking. One can also enter the country in the search box.

If you didn’t know already (and I didn’t) the section labeled COTB is for “Clandestine and Other Target Broadcasts.” This isn’t an abbreviation you will readily find on Google.

The WebApp lists names and contact information for all the stations, something not included in the printed book.

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Radio Memory Systems

Posted on April 3, 2023 by Kevin

I have a number of radios that can store information in station memories, called “presets.” They all work differently. Here I include a brief review and say what I like best.

Radios use memories in two ways: to allow the radio user to store favorite stations for easy retrieval, and for automatic storage of stations found by the radio when scanning the bands. The number of memory slots and how they are managed varies between brands and between radios within brand.

ATS

ATS stands for “auto tune storage,” a feature where the radio scans some range of frequencies, and automatically stores the stations found in memory. ATS is convenient for the operator because they can do something else while the radio is scanning and then just go through what was found. The limitation of ATS is that some stations fade in and out, go on and off the air, or might be weak. Each of those conditions could cause a station to be skipped. ATS scans on shortwave often include only the international shortwave broadcast bands. A table at the end of the article indicates which radios have limited scans.

Following is a comparison of the memory systems in my radios (radios are listed alphabetically):

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