Category Archives: AM

New from Heathkit: the Explorer Jr TRF AM radio receiver kit

The Heathkit Explorer Jr. (Image Source: Heathkit)

Yes, the legendary Heathkit company is back and their first kit is a simple Tuned Radio Frequency (TRF) AM/mediumwave analog receiver: the Explorer Jr.

I knew Heathkit was back in business and under new management, but hadn’t heard any updates as of late. Their president, Andy, just sent a message to the “Heathkit Insiders” group explaining what the team has been up to:

“We’ve designed and developed a wide range of entirely new kit products. We authored the manuals for these kits, complete with the beautiful line art you rely on, preserving and respecting our iconic historic Heathkit style. We developed many new inventions and filed patents on them. We relocated Heathkit, and set up a factory, and a warehouse, and offices, in Santa Cruz, California, near Silicon Valley. We built the back office infrastructure, vendor and supply chain relationships, systems, procedures, operations methods, and well-thought-out corporate structure that a manufacturing company needs to support its customers, to allow us to scale instantly the day we resume major kit sales. All this effort enables us to introduce a fleet of new kits and helps ensure Heathkit can grow, prosper, and continue to bring you great new products for a very long time.”

The Insiders’ message goes into much more detail–I would encourage you to contact Heathkit about joining this group.

The big news in this message was the launch announcement of the Explorer Jr. kit which can be ordered from their website now. The price is $149.95 plus shipping. Heathkit anticipates a 30-day shipping time for the first set of orders.

Here’s a description of the kit from their website:

A Radio Kit Whose Time Has Come.

Again.

When Heath started designing & selling do-it-yourself airplane kits shortly after the Great War, the state-of-the-art in radio was the Tuned Radio Frequency (TRF) design.

A TRF radio was a great deal. If you had a great deal of money. A TRF receiver became a fixture in the homes of families around the world, receiving the news and music AM broadcasts of the day. A family AM radio was a big investment — $100 to $625 in 1929 dollars. (With inflation, that’s $1,400 to $8,700 in today’s dollars.) Of course, at that price radios also were beautiful. They were made of fine wood, and designed to last. Radios were a visible and attractive furnishing you could be proud to have in your living room or parlor.

Heathkit’s TRF radio is a great deal. And a great deal of radio. This Explorer Jr^TM radio is modeled on the original TRF designs, but better. You get to build it yourself. It’s safe and simple enough for beginners to assemble and understand. But it receives AM broadcast stations with performance superior to the vintage radios of 1930.

With the number of Heathkit enthusiasts out there, I suspect this first run of kits won’t last long. The kit trim is available in six colors: Silver, Cranberry, Cucumber Green, Plum Pie, Sapphire Blue, and Tangerine.

Click here to view and order the Explorer Jr on Heathkit’s webstore.

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Radio Kiribati and WiFi Radios

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Many thanks to SWLing Post reader, Paul Walker, who writes:

Thomas.. I know this isn’t quite SW news anymore, but Radio Kiribati usedto be on SW a while ago and is now on AM.

I just found out something to those of us interested in Pacific radio signals. Radio Kiribati 1440 JUST started a live web stream…JUST…as in, like within the last few days!

The audio levels can be a bit loud and overdriven at times, but i am corresponding with their Chief Engineer and the Radio station manager at the Broadcasting & Publications Authority in an effort to get levels set just right.

The audio is average and I wouldn’t expect much more, quality wise, then what they’ve got now.. as most of these stations have hare basics when it comes to some equipment.
The Radio Kiribati stream was just added to the Reciva.com database for internet radios and should be there soon if it isn’t already.

The stream is at http://202.6.120.13:8000/ The stream itself is of amazing quality at 64k vorbis, which sounds good to my ears via my CC Wifi Radio and CCrane Senta speaker.

Radio Kiribati only broadcasts local programming at certain times of day. Sometimes I’ll hear Radio New Zealand International outside of local broadcasting, other times I won’t.

TX times are as follows…most of their programming is in their native language, which is Gilbertese according to Wikipedia. It’s a Micronesian language of the Austronesian language family. They do three segments of English broadcasting every day, some 30 minutes long and one is an hour long.
Kiribati is UTC+14… at 416pm Thursday in Southwest Arkansas, where i am.. it’s 916am Friday morning in Kiribati.

Morning: 0700am to 0830am. English at 8am

Lunch: 1200 noon to 1330. English at 1300

Evening: 1700 to 2130. English at 1800

Feel free to post this to your own blog, website, Facebook group or page.. let’s spread the word!!

Thanks, Paul!

WiFi radios

Though pricey, I’ve heard the Pure Evoke F4 has fantastic audio and a meticulously curated database of Internet streams.

This is one of the benefits of Wi-Fi radios and Internet streams: the ability to hear “local” stations–many of which used to broadcast on shortwave–from all corners of the globe.

I’m seriously considering purchasing a Wi-Fi radio for my wife to make it a little easier for her to listen to Internet streams in her office.

I’ve been looking at the C.Crane CC WiFi radio, the CC WiFi 2, the Grace Digital WiFi Music Player and the (much pricier) Pure Evoke F4 which my buddy, John Figliozzi, so highly recommends.

Any suggestions and recommendations are most welcome.

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Jeff gives high marks to the Sangean PR-D4W

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My pal, Jeff McMahon, over at the Herculodge, has just posted a video review of the Sangean PR-D4 portable radio. In summary, he writes:

“It’s a great radio with top FM, AM, and speaker sound. It blows away my C.Crane Radio-2E. Lack of illumination, however, makes it less than ideal as a bedside clock radio.”

Wow! I’m most impressed that Jeff places the PR-D4W (which retails for $69 on Amazon) above the venerable CCRadio-2E (which retails for $169 on Amazon) in terms of AM performance.

I just checked and it appears that Universal Radio also retails the PR-D4W for $69.95.

Follow Jeff at the Herculodge and on YouTube.

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The Sangean ATS-909X: Marty’s bedside radio review

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SWLing Post reader, Marty (W5MRM), comments:

I recently picked up a Sangean ATS-909X to use as a bedside radio.

This blog post inspired me to put together a video review of the ATS-909X as a bedside radio. The video review can be found on my youtube page [or via the embedded player below]:

Great video, Marty, and thanks for the thorough review!

You can follow all of Marty’s videos on YouTube by visiting this page.

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Jeff’s bedside radio search ends with the Sangean CL-100

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My pal, Jeff McMahon, over at the Herculodge writes:

A week ago, my Sangean WR-2 was fried when the electric company surged my house. I replaced it with the Grundig S350DL but it drifted too much.

I then used my superior Crane-SW radio (same size as the big Grundig) and guess what? It died! Those cheap radios today seem to die after 5 years or so.

So I looked through the myriad of unused radios in my cabinet and unearthed a Sangean CL-100 purchased in 2011. For whatever reason, it no longer works with batteries (old double As were left in there and leaked a tiny bit but compartment looked clean enough), so I plugged it in and it works.

FM is better than my Sangean WR-2. I think it has a DSP chip.
AM is better with low background noise, amazing for a radio this small.

Speaker is not as good as the WR-2, but it’s clear and okay since I listen mostly through earbuds.

Tiny footprint on my bedside table, which I like.

The menu system is easy enough to use though I wonder if down the road I’ll encounter bugs.

I bought this for about $45 and now it’s about $12 more.

It really suits my needs.

[A] man needs a strong performing bedside radio. That’s the backbone of a collection.

Indeed it is, Jeff!

I see why you like the CL-100. For a bedside radio, the flat/horizontal form factor also makes it less susceptible to being knocked over when you reach for it in the dark.

As for battery operation, you may try removing some of the corrosion on the battery contacts with a file or something mildly abrasive. I’d also hit it with a little Deoxit. (Though knowing Jeff, he’s probably already on this.)

Having your Sangean WR-2 fried by the power company is bad enough, but then finding out your C.Crane CCradio-SW isn’t working just adds insult to injury.

I should note that, in general, I think C.Crane products are built as well as most others on the market.

I often wonder if premature product failures have less to do with poor quality control and more to do with the lead-free solder electronics manufacturers are forced to use these days.

Many moons ago, a friend sent me this article which outlines concerns about the use of lead-free solder in the military and aerospace industries. It’s worth a read and certainly points out inherent flaws. I often wonder if nearly all of our modern consumer electronics are prone to fail within a decade; you know, planned obsolescence at its worst. Perhaps I’m overreacting.

When I build kits or repair electronics, I only use traditional lead-based solder. Not only is it easier to use, but I feel it will last longer.

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The Oxo Good Grips Turntable for the Mediumwave DXer

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SWLing Post contributor, Robert Gulley, writes:

I recently purchased an Oxo Good Grips Turntable, 16” from Amazon. As the photos show, the size of the turntable can hold a fairly large radio (CC Radio EP and Select-a-tenna) on the turntable in almost any configuration. (Of course the CC Radio EP doesn’t need the Select-a-tenna, just used for illustration purposes for size.)

At $16.99 I think it is a good bargain, and seems quite capable of turning smoothly even with this amount of weight.

Click here to view on Amazon.com.

Many thanks, Robert! I think that turntable is large enough to hold pretty much any portable radio; thanks so much for the photos (especially the one your kitty cat photo bombed, above!). I have several OXO products in my kitchen and have never been disappointed with quality, so I expect this turntable will last you a very long time.

Readers: If you haven’t checked out Robert’s radio blog, All Things Radio, I encourage you to do so!

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Guest Post: Joris’ home brew Si4835-based receiver

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Many thanks to Joris van Scheindelen (PE1KTH)–an SWLing Post contributor from the Netherlands–for the following guest post:

High Tech AM-FM DSP Receiver From

The old mode AM is still an interesting mode for amateur radio communication, also in amplitude CW.

Building your receiver is not difficult and quite fun. The semiconductor industry makes interesting integrated receiver chips today that will be useful for an AM receiver. Not only for broadcast reception but also for amateur AM reception or as part of an AM transceiver.

Silicon Labs also makes Si4734/35 receivers; these need a CPU to control the receiver, but are of interest for amateur use because the frequency can be tuned in 1 KHz steps and the audio channel bandwidth in 7 steps. There is no need for the transmitter to be on the receiving channel…

Si4835 AM-FM receiver

Looking for a small SW broadcast receiver design, and pocket size, I came to the excellent range of modern DSP receivers in a single chip from Slicon Labs.

I made a test bed set up has been made for the Si4835 AM-FM receiver.

The target specification was:

minimal components,
no micro-controller,
low power,
backlash free mechanical tuning,
good sensitivity,
earphone,
robust housing,
a short and small antenna system for outdoor use,
and minimal controls.

The Si4835 makes miniature design possible on a PCB (see photo Figure 1).

The red Dip (band) switch was replaced by a rotary switch in the final receiver design (Figure 4).

The receiver power is minimal 2 x 1.2 = 2.4 volts or a one cell LI-ION accu.
5 volts is the maximum for the Si4835 chip; current consumption is 30 mA.

Fig 1. Testbed setup for the Si4835.

The receiver has an RF pre-amplifier transistor and the LF amplifier is the TDA7050T.
All receiver functions are in the chip; the schematic is very simple and can be built with minimal components (see schematic appnote AN555 Fig 2. below).

Only an LF amplifier has to be added to complete the receiver.

Fig 2. Receiver schematic Si4835 in the AN555 application note.

The Si4835 receiver has the following frequency bands–they are divided in sub bands 800 or 900 KHz wide (See Figure 3). The frequency step tuning is 10 kHz on AM, following the international broadcast raster standard.

Fig 3. Si4835 receiver sub bands.

This means there are 80 or 90 receive channels in the sub bands and make finding the BC stations on the scale more easy. The 10 KHz scale steps are linear. The frequency stability is locked to the 32 kHz X-tal via the synthesizer so there is no frequency drift. The AM LF audio channel is 5 kHz wide set by the DSP filter. Volume control can be done width 2 up-down push switches or by a LF potentiometer..

Fig 4. The experimental pocket aluminium receiver housing on PCB2.

Receiving results

I have been testing many hours and I am surprised about this little receiver.

The receiving results are excellent on FM and AM and signals of 2 -3 uV are well received.

Also the audio quality is good–especially on FM. As can be seen in the frequency table the 40 and 20 meter band are in the range. Clear AM phone amateur transmission has been received when the transmitter was tuned on the 10 kHz raster in 40 meter band on AM.

Also AM modulated CW signals can be received bud not un-modulated carrier CW–they sound “plop…plop”.

The 5 kHz wide LF channel is a bid too wide so many CW signals pass through the audio at the time, but if AM modulated that should not be a serious problem.

The broadcast stations in the SW bands (when the daytime conditions are good) up to 20 MHz are good and strong.

Conclusions

The Si4835 receiver can be a fine broadcast receiver for outdoor work and if an AM transmitter is tuned in the 10 kHz raster this receiver can also used for amateur phone reception.

Addendum: The Si4734/35 is a better amateur AM Receiver

The Si4734 and Si4735 are a better receiver choice for amateur AM purpose because the frequency tuning can be done in 1 kHz steps. Also the BW of the LF channel can be adjusted to 1 kHz wide.

In Fig 5. from the programming APP note you see the code 0X3102 AM CHANNEL_FILTER it is possible to adjust the audio width by sending this code to the Si4734/35.

Fig 5. From the programming APP note

The LF bandwidth can be set on 1, 1.8, 2.5, 2, 3, 4 and 6 kHz wide.

This is excellent for modulated CW and AM phone discrimination in the audio channel.

The disadvantage is the need of an CPU and LCD display, “away from a minimalistic design”.

See also the note 1 and 2 improved 100 Hz rejection. See data sheet of the Si4734/35.

It look like that this receiver is a good receiver for building a modern AM-(AM)CW receiver or in a transceiver application. Tuning can be done digitally.

Think about this receiver [and the Si4835 chipset] when you intent to build a high tech AM – T/RX.

73 ‘ Joris van Scheindelen PE1KTH

What a fantastic home-brew receiver, Joris! I love the simple design of your receiver and the fact that it’s quite portable. Thanks so much for sharing your notes and documentation.

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