Category Archives: AM

Frank shares 1991 recordings and original notes of station IDs and interval signals

SWLing Post reader, Frank, writes from Germany:

First let me say that I enjoy your blog a lot.

After a 2005-13 hiatus, I have rediscovered a childhood hobby and your reviews have helped me find my way to the post-Sony portable shortwave radio markets.

First, I obtained my “childhood dream” radio (Sony ICF 2001D), because at the time I made these recordings I was still in school and 1300 DM would have equaled over 1 year of pocket money, so a Supertech SR16HN had to do. I thought I got some fine results with this Sangean-Siemens re-branded receiver then, using a CB half-length antenna, a random wire, and much endurance.

The Supertech SR16HN (photo: Radiomuseum.com)

I kept regular logs throughout the years, wrote to 50 international and pirate stations for QSL and compiled this cassette.

A few years before I got that trusty SR16HN, however, I recorded a few number stations (such as G3, Four Note Rising Scale etc) with an ordinary radio cassette recorder, and in 1991 I put them onto this tape as well. The other recordings are done with the same radio placed right in front of the SR 16HN.

Feel free to make use of these recordings. Most of it are the well-known international state-owned shortwave stations of the past; plus European pirates; plus number stations; and at the end, a few (off-topic) local Am and FM stations interval signals.

As I said, this collection I made shortly after the Wende/reunification period, when all former-GDR state broadcasters changed their names, sometimes more than once.

Please continue your good work on the blogs! Weather permitting I am often outside cycling and always have the tiny Sony ICF 100 with me (which I call my then-student’s dream radio of the later 90ies).

Cassette Side 1

Frank’s original hand-written notes. Click to enlarge.

Click here to download Side 1, or listen via the embedded player below:

Cassette Side 2

Click to enlage.

Click here to download Side 2, or listen via the embedded player below:

Wow! Frank, what a treat to listen to all these station IDs!

I had forgotten how many interval signals have changed over time and how many, of course, have disappeared. This tape represents a flood of nostalgia for me.

I should add, too, that I’ve enjoyed hearing so many IDs in German. It’s funny, but we all get hooked on listening to language programming from our native or second languages. It makes me realize just how many broadcasters used to have German language services.

Again, many thanks, Frank, for taking the time to digitize these recordings and scan your original hand-written notes. This stuff is invaluable, in my book!

BBC sets plans for next decade

5 Replies

Many thanks to SWLing Post reader, Bill, for sharing a link to this article which summarizes the BBC’s plans for the next ten years.

BBC director general, Tony Hall, said the corporation will become an “open BBC for the internet age”.

While Hall was quick to add that funding cuts would equate to “the loss or reduction of some services” he also highlighted several efforts that would include shortwave and mediumwave broadcasts, including:

“Significant investment” in the BBC World Service, including a daily news programme for North Korea and more broadcasts to Russia, India and the Middle East
A news service for Ethiopia and Eritrea on medium wave and short wave

Of course, we can expect more cuts to BBC World Service shortwave broadcasting over the next ten years even if it wasn’t specifically mentioned in Hall’s speech. If we’re lucky, the BBC will continue to broadcast into those parts of the world that still rely on shortwave. Specifically mentioning North Korea, Ethiopia and Eritrea appears to be a nod in that direction.

Click here to read this article on the BBC News website.

Also, The Guardian has posted the full text of Tony Hall’s speech. It’s worth reading.

The New York Times: breaking news and antique radios

4 Replies

Many thanks to my buddy, David Goren, who recently discovered that the New York Times Store is now selling fully-restored antique radios.

Pricing is not for the faint of heart–at time of posting, prices ranged from $395 to $23,000 US. Each radio is beautifully presented, with a full description, and carries a one year restoration warranty. For an additional $95, many models can be modified with an AUX in audio jack.

While these radios are well outside my meager vintage radio budget, I must say that I’ve thoroughly enjoyed looking at the photos and reading the descriptions.

Click here to view on the NY Times Store.

Using synchronous detection and notch filter to eliminate het noise

5 Replies

The lighter shaded side of the AM carrier indicates a lower sideband sync lock. (Click to enlarge)

A few days ago, I tuned to 9,420 kHz and found a relatively strong signal from the Avlis transmitter site of the Voice of Greece. The broadcast was quite clear until a heterodyne (het) tone popped up out of nowhere.

I checked the spectrum display of my Excalibur to find two steady carriers located about .5 kHz off each side of VOG’s AM carrier. I assume this may have been a faint digital signal centered on the same frequency as VOG.

The noise was annoying, but SDRs (and many tabletop radios) have tools to help mitigate this type of noise.

The het tone was originating from both sidebands of the VOG AM carrier (see spectrum display above). I had planned to use my notch filter to eliminate the noise, but I had two carriers to notch out and only one notch filter.

VOG AM carrier

Synchronous detection to the rescue…

The simple solution was to eliminate one of the carriers using my SDR’s synchronous detector which can lock to either the upper or lower sideband. In this case, it didn’t make any difference which sideband I locked to because both had similar audio fidelity and were otherwise noise free. In the end, I locked to the lower sideband, thus eliminating the het in the upper sideband.

Next, I enabled my notch filter and moved its frequency to cover the annoying het carrier in the lower sideband; I kept the notch filter width as narrow as I could to preserve VOG’s audio fidelity. You can see the notch filter location and width in the spectrum display above (the notch filter is the thin yellow line).

I should note here that the great thing about using an SDR–or tabletop receiver with a spectrum display–is that you can see where the noise is. I was using my WinRadio Excalibur, but pretty much any SDR in my shack could have handled this task.

The results? No het tone and I was able to preserve the great audio fidelity from the Voice of Greece broadcast!

Here’s a 3.5 hour recording I made after cleaning up the signal. I believe at one point in the recording, I switched off the notch filter to demonstrate how loud the het tone was:

Moshe restores a Ben-Gal “Duet-Stereo”

1 Reply

Many thanks to SWLing Post contributor, Moshe, who writes:

About 2 weeks ago, a very good friend called me and exclaimed, “you just have to see this radio…I’m keeping it for you!”–so, I drove to his aunt’s house and saw this beauty.

After hauling the radio to my place, I started to check it out, to see what would be needed for restoration; it was working, with bad contacts, poor frequency response and low output.

I took hi-res pictures of this radio, some during restoration. Now the radio sounds great. It has been recapped, a couple of bad resistors and bad wires replaced, contacts have been cleaned, and some good cleaning for the chassis as well.

As I wanted to keep the original appearance of the chassis, I kept the original filter capacitors on board, but disconnected them from the circuit, added terminal strips and new capacitors from underneath.

The radio uses an EF85 tube as the RF stage. With the addition of a grounding connection and random wire antenna, it’s very sensitive on shortwave.

About the Ben-Gal Duet-Stereo:

It was made in Israel by Ben-Gal, a label inside shows it was made at 12th of December, 1965.

It is a console model with record player. As the model name suggests, the amplifier and record player are stereo (though the tuner is not…).

The radio has longwave (marked in meters), mediumwave (marked in meters) and 3 shortwave bands (with megacycle and meter band marks).

The shortwave bands overlaps with each other, so cover is continuous:

SW3 2.3MHz to 6MHz,

SW2 5.5MHz to 15.5MHz,

and SW1 14.5MHz to 23MHz.

Many thanks, Moshe, for sharing photos and this description of this beautiful Ben-Gal Duet-Stereo. I bet the audio fidelity is amazing. My father has a 1960’s console–with a similar configuration–made by Admiral, though it was limited to mediumwave and FM reception. Some day, I will try to restore it to its former glory!

Thanks for the inspiration, Moshe!

DSP noise may come from clock and data line harmonics

3 Replies

In response to our review of the Sangean ATS-405–which noted DSP noises on 800 and 1600 kHz–SWLing Post reader, Steve Yothment, comments:

“Yes, modern radios usually have a micro communicating with the DSP IC through I2C communications.

The inter-IC communications includes a clock and data line. The clock for I2C is typically 400 kHz nowadays. Harmonics from this clock line are probably the source of the interference.

The manufacturer should have designed the product to ensure that this interference does not occur. It may be that they resolved it at one time but with limited manufacturing quality and component substitutions that often occur in mass production, the problem is occurring now even though it may have looked OK earlier in development. At least, that is my experience with such things. (I used to design car radios for the Panasonic Company.)

You can learn more about the I2C bus at https://en.wikipedia.org/wiki/I%C2%B2C.

Many thanks for your comments, Steve! I recall a similar metronomic sound on another DSP-based radio, but can’t remember which model. I need to dig through my reviews as I’m sure I noted this. I believe checking 400, 800 and 1600 kHz will become a standard checklist item when I review DSP-based radios.

The Aiwa FR-C33 AM\FM\WX portable radio

7 Replies

A few weeks ago, SWLing Post contributor, Ron, sent me an eBay listing for a radio with which I was not familiar: the Aiwa FR-C33.

Ron wrote:

“I know you are primarily HF but here is something rather special and unique and inexpensive:

Aiwa’s response to C-Quam in the late 90’s was “AM Wide.” Apparently all this meant was a somewhat wider Murita ceramic filter.

But…the bandwidth just matches the 10,200 cycle limit imposed on AM stations today…try a Sony SRF-42 or SRF-A1 C-Quam receiver at night on today’s band and note that they’re just too wide.

I have one of these and can tell you the build quality is great…it has a tone control and on Sony Walkman headphones stations like WSM are just flat-out unreal in sonic quality…the speaker isn’t bad, either.

A nice big ferrite bar makes it a bit of a DX machine, too.

FM is also very good; even the weather-band add-on works too.

Very much worth a go for your collection and enjoyment[.]”

Aiwa-FR-C33-Back I’ve been enjoying the FR-C33 for a few weeks now; Ron’s assessment is spot-on.

The FR-C33 produces clear audio via its internal speaker, but where it really shines is with a pair of good headphones plugged in. Though it has no “Mega Bass” feature like many radios of its era, the Aiwa produces great bass tones via a good set of “cans” (I’ve been using my Sennheiser HD 428s).

The FR-C33 has a very useful tone control with a smooth, wide spread between the full bass and treble settings.

All of the FR-C33’s controls are fluid and functional.

AM (mediumwave) reception is truly fantastic. I find that the analog tuning wheel is easy to use and there’s enough room for the needle to easily travel across the dial without skipping stations inadvertently (a problem I often find with smaller analog portables).

It really shines, however, when you can center on a local broadcaster with a quality AM signal. While the FR-C33W doesn’t receive C Quam stereo, of course, its wide AM filter offers up excellent fidelity.

FM reception is also sound. While I haven’t done a formal comparison on FM, it receives my benchmark FM stations with ease and produces great audio fidelity via headphones. Sensitivity-wise, it might lag slightly behind some of the better DSP-based radios out there, but for an inexpensive analog receiver, it must be at the lead of the pack.

Ron, I really appreciate the recommendation–thank you! The FR-C33 is a keeper for sure.

Though these don’t pop up regularily on eBay, you can search for an Aiwa FR-C33 by clicking this link.