Category Archives: Radios

eBay sighting: Braun “Wall Unit” by Dieter Rams

Dieter Rams’ office with mounted Wall Unit. (Source: Campsite studio)

Many thank to my buddy, David Korchin (K2WNW), who sent the following eBay link:

Dieter Rams masterpiece Braun “Wall Unit” Wandanlage TS45 TG502 reel L470 PCS5

While I love Dieter Rams’ designs, and no doubt this is a very rare piece in “almost perfect shape,” it is certainly well-beyond my budget at $11,000 US plus $600 shipping.

Admittedly, though, if I were building a modern house and wanted a feature piece of functional artwork, the Braun Wall Unit may very well fit the bill. Most of Rams’ designs certainly seem to hold or increase in value over time.

For now, I’ll just admire this design from a distance. Curious if it’ll fetch its BuyItNow price. Thanks again for sharing this one, David!

Guest Post: Richard tests the frequency stability of the Tecsun PL-880

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Many thanks to SWLing Post contributor, Richard Langley, for the following guest post:

Frequency Stability of My Tecsun PL-880

Recently, while recording the audio on a particular SW frequency unattended over night, I decided to set my Tecsun PL-880 in USB mode with the 3.5 kHz RF bandwidth setting as I had previously noticed splatter QRM from a station 10 kHz below my frequency of interest. I adjusted the frequency to the nearest 10 Hz for natural-sounding voice. On playing the recording, I was disappointed to find that the signal had drifted in frequency and although speech was still recognizable, music was distorted.

I decided to try to measure the stability of the receiver by recording the Canadian time signal station CHU on 7850.00 kHz in USB mode (CHU has no LSB component) over night for over nine hours. The receiver was operated with just its telescopic whip antenna indoors and the audio was recorded with a Tecsun ICR-100 radio recorder / digital audio player. I wrote a Python script to compute the audio spectrum of each one-minute segment of the recorded files using a fast Fourier transform (after removing a DC component). The script then looks for the largest peaks in the spectra centred on a specified frequency and prints out the frequency (to the nearest Hz) and amplitude of the peak. In case the signal has dropped below audibility, a threshold is set and if the detected peak is below the threshold (likely just detecting the random noise background), it is skipped. The specific centre frequency I was looking for was 1000 Hz, the frequency of the tone used to mark each second of the CHU broadcast except when the voice announcement and digital signal are transmitted. In AM mode, the spectrum would consistently show a peak at 1000 Hz but in SSB mode, the peak will vary depending on the receiver frequency setting and the actual frequency of the receiver’s oscillator.

The plot below shows the received CHU one-second tone frequency as a function of time (UTC) from when the receiver was first switched on.

StabilityPlot-CHU1000hz

It shows the tone frequency started out at about 1046 Hz slowly dropping in the first half hour to about 1012 Hz and after about an hour stabilized to 1011 Hz ± 1 Hz for the better part of an hour. (This shows that you may have to allow a receiver to “warm up” for perhaps up to an hour before attempting anything close to accurate frequency reading at the order of 10 Hz.) But then, over the course of the next seven hours when the signal was audible, the frequency slowly rose ending up at about 1034 Hz. The variation might be affected by the ambient air temperature (but this should have been nearly constant), air flow around the receiver, and perhaps the charge level of the receiver’s battery. On several occasions, I have turned the receiver on (after being off for many hours) and seen a CHU frequency offset of only 10 or 20 Hz. So, I intend to repeat this experiment sometime to check on the day-to-day frequency stability. This frequency stability measurement technique could also be used with WWV/WWVH by recording the 440, 500, or 600 Hz tones broadcast at different times during the broadcast hour.

Of course, it’s also possible to check the receiver’s frequency offset in real time by switching between AM and SSB modes while adjusting the receiver frequency in 10 Hz steps until the signal sounds the same in both modes. There is also freely available computer software for various operating systems that can display a real-time spectrum of audio passed to it through a microphone or line input. So, a CHU or WWV/WWVH test using such software could also be performed in real time. And alternatively, by tuning say exactly 1 kHz away from the transmitted carrier frequency in SSB mode, the software can be used to measure the audible heterodyne frequency to better than 10 Hz — even 1 Hz. This frequency can then be added or subtracted as appropriate to the dial reading (assumed accurate or with a noted offset) to get the exact transmitted carrier frequency.

By the way, it is possible to calibrate and reset the PL-880 using the procedure documented on the SWLing Post (click here to view).

As a side benefit of the analysis I carried out, we can also look at the quality of the received signal over the recorded interval. In this case, it is a measure of the level of a particular audio frequency rather than the RF signal+noise level we usually get from the receiver S-meter or other signal strength display. This is illustrated in the plot below for the CHU recording. As you can see, reception was mostly quite good between about 02:00 and 04:00 UTC and then became fair but above threshold level until about 05:30 UTC.

The signal was then essentially inaudible up to about 08:00 UTC when with bouts of fading it became audible again for an hour or two with sunrise approaching.

— Richard Langley

Guy discovers the $13.99 Basbon DS-858 shortwave radio

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SWLing Post contributor, Guy Atkins, writes:

I spotted this new listing on Ebay today, and was wondering if it’s a new model, or perhaps a repackaged Tecsun PL-606? It’s lacking the rotary tuning knob and has a smaller display than the 606 however. It also has two rows of main buttons rather than three:

http://ebay.to/1KGjfrN

Curiously, the seller doesn’t even list the brand name in their auction title; it’s only noted in the pictures. However, “Basbon” isn’t exactly a brand of communications receivers with a long, proud tradition :^)

For $13.99 including shipping the the USA it’s hard to go wrong, so I’ve ordered one.

[…]Three features that caught my eye with the little Basbon radio are that it’s DSP based, it has LCD backlighting, and shortwave frequency coverage down to 3200 kHz. There are 20 memories and a sturdy-looking whip antenna that rotates 360 degrees, too.

I can’t wait to get ahold of this and open it up! I wonder which SiLabs chip it uses?

Thanks for the tip, Guy! I’m also very curious about this little portable–indeed, curious enough, I purchased one, too. Guy and I will compare notes and I’ll post an update after I receive the radio. It’s being shipped via ePacket from China, so transit time will be roughly two weeks if not held up in customs.

Frankly, my expectations are very low, but like Guy, it’s a little too tempting at $13.99 shipped!

Click here for a direct link to the Basbson DS-858 on eBay—click here to search for the DS-858 should the current item number expire or sell out.

Dr. Phil’s radio articles: portable SDR and pocket DX

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SWLing Post reader, Dr. Phil, recently contacted me regarding a collection of articles he’s written about DXing and radio modifications.

His site actually has a number of useful articles that I’ll plan to convert to future posts, with his permission.

I asked Dr. Phil for links to two of his most popular publications. He replied:

My two big recent articles are shown below. One is about “Pocket Radio DX”: using under-$20 radios to DX (started in 2003). Click here to download as a PDF.

The other is about using an $18 NooElec TV-tuner as a MW and shortwave receiver. Click here to download as a PDF.

Brilliant! Thanks so much for sharing these, Dr. Phil!

I actually have a Sony ICF-S10MK2, which I consider to be a capable and useful little AM/FM receiver for the sub $20 price. I’ve also been very tempted to purchase an RTL-SDR dongle, so I may go ahead and bite the bullet on one of the NooElec SDR dongles.

Mike’s thrift store find: a Panasonic RF-888

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Mike's Panasonic RF-888 (left) and his GE Super Radio II (right)

Mike’s thrift store Panasonic RF-888 (left) and his GE Super Radio II (right)

SWLing Post contributor Mike (K8RAT) writes:

I happened upon a good find of a vintage radio recently when I visited my local Goodwill store in a small city in Ohio.

Among the electronic equipment on a shelf I discovered a Panasonic RF-888. I was not familiar with this radio. The large speaker along with switches and knobs for features found on the better radios impressed me.

The price on the sticker read $3.50. I paid at the counter and motored away not knowing what a bargain I had received.

The RF-888 audio is very good on FM and good on AM. Sensitivity and selectivity are very good on both bands. The tuning meter is useful.

I recommend visits to local second-hand stores. You never know what you might find.

Mike, K8RAT

Many thanks for sharing this story, Mike, as it provides a good lesson for us all: never pass by a thrift store! I’ve never had the good fortune of finding a gem like the RF-888–or a Sony ICF-2010 like Vlado–but I shall keep searching.

Panasonic RF-888s sell on eBay for $100 US and higher–at $3.50, I’d say Mike snagged a deal.

Silicon Labs DSP chip homebrew receiver

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The Silicon Labs Si4730 series DSP receiver chip powers many of the portable shortwave radios currently on the market.

Manufacturers are not the only ones implementing the chip in receiver design, however; radio enthusiasts are too.

I recently discovered this short video by a Japanese hobbyist who implemented the Si4734 in his receiver design:

While I don’t speak Japanese, the author also has a webpage of detailed design notes you might check out (click here to view). I used Google translate for a rough English translation of the page.

Have any readers made a homebrew receiver from a Silicon Labs DSP chip? If so, please comment!

Click here to download the Si4734 product information sheet.

Moshe’s early birthday gift: a Philips 90AL765

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SWLing Post contributor, Moshe, writes:

After reading your post about your Panasonic RF2200 pre-birthday present, I decided I want to do the same. The radio I chose has a story behind it…

My Grandfather had the same exact radio. I used to play around with the radio as a child, (especially with the shortwave bands, looking for number stations…). When my Grandfather died, about 23 years ago, the radio disappeared.

I decided this is the radio I want for my birthday. I could not remember the maker of the radio, nor it’s model, but I remembered how it looked.

I spent many days looking for all variations like “portable transistor radio” and so on, until I found a photo on the Internet: I was looking for a Philips 90AL765 radio.

I found it on Ebay. A very kind seller from Australia had it.
I purchased and receive the radio on the 26th of June (my birthday was the 12th of July). As soon as I got the radio, I opened it up; it needed cleaning (the case itself and the contacts).

After cleaning the contacts and washing the case, the radio runs (and looks) like new. I thought I would have to recap the radio, but it sounded perfect and without even a hint of hum, so I left it as it is.

It has the volume and tone knobs missing, but it can be operated with no problem. Sound quality is amazing (I added a video of the radio playing All India Radio on 6155 kHz)–it works very well on all bands and is very sensitive. By ear, the bandwidth sounds like 8 kHz or more. Radio bands are: MW, SW (2 bands) And FM.

The shortwave band is divided in two: SW1: 2.3MHz- ~7.4MHz, SW2: ~9.4MHz- 22.5MHz. For fine tuning on shortwave, the radio has a “Fine Tuning” control, which is a potentiometer connected to a varicap.

If you place the control in the middle (It lacks a detent spot) and tune in a station, this control will put you spot-on (the receiver is very stable).

Some info about the radio: According to Radiomuseum.org, the radio is dated to 1977, and was made in Austria (mine and my Grandfather’s were made in Singapore).

It contains 13 transistors, 3 of them are can transistors (not plastic).

Tuning is slide ruler type, and the only connection is A DIN5 for recording (wired for mono).

The radio can be operated from 4 D cells, or directly from AC (in the picture you can see the transformer). It can be operated from 230V or 120V. Note that if you move the plastic pin cover from the left pin to the right one, the center pin remains visible at all times. Also you will have to move the plastic cover piece on the back to the left.

The Ferrite is 14cm long, the telescopic antenna is 79cm fully extended, and it has an elbow joint that allows you to place the radio in your lap and still the antenna will point up with no problem. Only thing is that if the antenna is extended, the handle cannot change position since the antenna is in the way.

Width of the radio itself is 29cm (31cm with the handle and the knobs).
Depth is 7cm.
Height is 16.5cm (21cm with the handle).

All in all, it is a very fine radio and I love it!

Moshe, thanks so much for sharing your story!

Perhaps, one of the true virtues of sites like eBay is that they allow us to search the world for somewhat obscure devices that have such a strong family and nostalgic connections. Congratulations on your find!