Category Archives: AM

How to replace a noisy wall power supply

Regarding noisy switching power supplies, SWLing Post reader, Dan Lewis, comments:

“Google the following: “Jameco linear wall transformer”, and you’ll find a suitable non-switching replacement.

Jameco still has a number of linear transformers in their catalog at reasonable prices. I haven’t bought anything from them in many years but when I dealt with them frequently a number of years back they were always reputable.”

Many thanks for your suggestion, Dan! Jameco is a reliable company and I’ve also been a long-time customer. If you know how to pick the proper power supply for your radio (or any other electronic device) click here to view a list of regulated linear supplies on Jameco’s website. [Also note this follow-up post.]Otherwise, keep reading…

How to find a replacement AC adapter/power supply

When you purchase a replacement power supply, you must make sure that several properties match that of the device it will power, else you could cause damage.

There are four properties you need to match: voltage, rated current, polarity and tip size.

Voltage

Most consumer electronics are powered by and rated for 4.5, 5, 9, 12, or 13.8 volts DC. Of course, there are exceptions. It is important that you match the required voltage exactly. Most radios and electronic devices display their required voltage and voltage tolerance on the unit itself, on the supplied switching power supply, and/or in the owner’s manual.

Rated Current

Like voltage, rated current is usually displayed somewhere on the device, existing power supply or in the owner’s manual. Current is usually indicated in amps (A) or milliamps (mA). Unlike voltage, rated current on your power supply does not have to match the device exactly. You simply need to make sure the power supply meets or exceeds your radio’s required current.

For example, if your radio requires 800 mA (or .8 A) and you find a power supply rated for 500 mA, you should not use it. If you find a power supply rated for 2 amps (or 2000 mA), it exceeds the 800 mA rating, so you’re good to go!

Unlike voltage, your electronic device or radio will only draw the amount of current it needs from the power supply.

Polarity

Click here to read more about tip polarity. (Source: WikiPedia)

You’ll need to determine if your radio requires a plug with a positive or negative tip (a.k.a. center conductor).

Fortunately, manufacturers have long used standard symbols to make polarity obvious (see image).

You’ll typically find a polarity symbol printed on the back of your radio, near the plug-in point, in the owner’s manual or on the back of the existing wall adapter.

Note: Be very careful matching polarity! Some radios and electronic devices are not properly protected against reverse polarity; damaged can occur immediately after supplying voltage with incorrect polarity.

Tip/plug size

You need to make sure that the inner diameter and outer diameter of a replacement wall adapter will match that of your existing adapter.

This can be the most difficult property to match.

Occasionally, radio manufacturers will actually specify the tip size in their owner’s manual, spec sheets, or on the product page of their website. I’ve even had luck calling manufacturers and asking a technician for the plug size.

Specification sheets will typically indicate plug dimensions with an illustration.

Otherwise, you can always measure the existing power supply tip (both inner and outer dimensions) using calipers.

Once you have those dimensions, finding the appropriate replacement power supply is quite easy. Indeed, companies like Jameco provide specification sheets (click here for an example) that indicate dimensions for each power supply they sell.

Once you’ve matched the voltage, rated current, polarity and tip size, you can purchase a regulated linear power supply with confidence!

Keep in mind: there are most likely other devices in your home with noisy switching power supplies that could be causing radio interference. Check out my noise trouble shooting section of this article to help identify local sources of radio noise.

Update: check out this follow-up post regarding Jameco power supplies–not all are truly linear regulated.

Sangean blames AM interference on power supply and government regulation

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After the Sangean WR-15 received low marks for AM reception in an Amazon review, Bob of Sangean America replied that poor reception is due to the radio’s switching power supply–a design that is federally mandated.

Many thanks to Jeff over at the Herculodge for posting this (click here to read the full response).

It’s a shame the WR-15 can’t accommodate internal batteries as battery operation this would solve the problem.

If I owned the WR-15, I would simply replace the switching type power supply with a regulated power supply.

Looking at the back of the WR-15 (below), it appears it requires 12 volts DC, 1.2 amps and an adapter with a positive center tip. Though I’m judging this only from the image, the plug looks to be a common size. WR-15-back I bet I have a power supply that would fit the bill in my junk drawer.

Bob, at Sangean America, claims moving the radio at least one foot from the power supply should help. In truth, I believe much of the noise may be conveyed by the power cord itself, though I may be wrong.

It’s a shame Sangean engineers couldn’t compensate somehow for the noisy power supply as it seems this radio was actually marketed to AM radio enthusiasts.

Photos from the VOA Bethany Museum

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Immediately after packing up our table at the Dayton Hamvention, my buddies Eric (WD8RIF), Miles (KD8KNC), and I made the 30 minute journey to Bethany, Ohio, to visit the VOA Bethany museum.

Main entrance and front lobby (above).

Entering the transmitter control room.

Eric pointed out an article on the future of shortwave radio I published last year that the museum has posted in the hallway next to the control room (above). What an honor!

The antenna switching array behind the main building (following four photos).

WLW (700 kHz) 800′ tower in the distance (above).

The satellite dish (above) was once used for VOA’s downlink/feed–now the West Chester Amateur Radio Association (WC8VOA) uses the dish for EME (Earth Moon Earth) contacts.

Back inside, WC8VOA has four full amateur radio operating locations stocked with Icom, Yaesu and Kenwood gear. The club president told us that an antique amateur radio station will soon be added.

Our docent took us on a tour of two vaults filled with vintage radio equipment and then a museum devoted to the legacy of WLW. The item in the photo above is a corona ball from one of the original towers–notice the holes from lightning strikes.

Example of an early radio kit (above).

A rare Third Reich radio (above).

When Ohio-based R.L. Drake Company stopped manufacturing amateur radio equipment, samples of their full product line were donated to the museum.

The Museum is planning substantial renovations to restore the VOA Bethany Station and become a first class institution. During the restoration, the Museum is only open one day per month to the public: The third Saturday of each month from 1:00 PM – 4:00.

Click here to view the museum’s new website.

Jeffrey re-caps his Hallicrafters SX-110

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The restored SX-110 sitting on the bookshelf in the shack.

Many thanks to SWLing Post reader, Jeffrey Fritz, writes:

During the summer of 2012 you were nice enough to run an article in your blog about my reviving a 1961 Hallicrafters SX-110 General Coverage receiver. The radio has continued to perform reasonably well during the last few years. However, recently I acquired several pieces of professional test equipment. That encouraged me to delve even deeper into the restoration of my old receiver from my novice ham radio days.

Over the past week, I completely recapped the SX-110 (except, of course, for the mica and ceramic caps as they still good, and the electrolytic caps as they were replaced in 2012.)

The SX-110 isn’t a complex receiver, but there are quite a few caps, so I worked methodically and carefully. I started working from the audio amp stage and continued working back through the IF stages and the BFO to the RF stage. I recapped each stage replacing the old caps with new Orange Drop caps. Each stage was tested before I moved on to the next stage. Here’s a photo of the recapped chassis:

Here are the capacitors that were removed from the receiver. Most are the old Bumble Bee caps–called that because of the color stripes that mark their value:

Virtually every Bumble Bee cap tested leaky and out of tolerance.

Next, I tested every tube replacing the weak or bad ones with NOS (New Old Stock) tubes. Every pot and switch was cleaned with DeOxit and moving parts were lubricated where appropriate. Finally, I did a complete re-alignment following the instructions in the Service Manual.

As with all vintage tube gear, restorations require patience, care and a decent knowledge of electronics. It’s easy to make a fair radio–even a good radio–into a disaster if you are not careful. Also there is enough voltage and current inside of the chassis of a tube radio to toss you across the room. So care is always the order of the day as is a VARIAC to bring the radio up to AC line voltage slowly.

The receiver now sounds as good as ever–perhaps even better than ever. It has marvelous AM audio and can pick up ham and broadcast stations on all bands with nothing more than a wire in my basement. It even does a decent job on SSB–something that I don’t recall it ever bring adept at in the past.

That say that you can’t keep a good man down. Similarly an old radio, with some new parts and some TLC, can run virtually forever.

I agree with you: you can’t keep a good radio down! Repair work is certainly the commitment we make when we fall in love with these old rigs. It’s a good thing that almost all of the parts are still available and relatively affordable.

Thanks again, Jeffrey!

When WLW was the one and only “Super Station”

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WLW’s diamond-shaped Blaw-Knox radio tower at night (Original photo by RP Piper via Creative Commons 2.0)

(Source: National Endowment for the Humanities)

For a Brief Time in the 1930s, Radio Station WLW in Ohio Became America’s One and Only “Super Station”

by Katy June-Friesen

When President Franklin Roosevelt, sitting in the White House, pushed a ceremonial button on his desk in May 1934, a five hundred thousand-watt (500 kW) behemoth stirred in a field outside Cincinnati. Rows of five-foot glass tubes warmed. Water flowed around them at more than six hundred gallons per minute. Dozens of engineers lit filaments and flipped switches, and, within the hour, enough power to supply a town of one hundred thousand coursed through an 831-foot tower.

Thus began WLW’s five-year, twenty-four-hour-a-day experiment: a radio station that used more power and transmitted more miles than any station in the United States had or would. The so-called super station—licensed by the new Federal Communications Commission (FCC) on a temporary basis—amped up the debate among broadcasters, government regulators, and listeners about how radio should be delivered to serve the “public interest,” a mandate laid out in the Radio Act of 1927, and influenced legal, programming, and technical decisions that shape the broadcast system we know today.

Since radio’s beginnings in the early 1920s, industry and government leaders promoted it as the great homogenizer, a cultural uplift project that could, among other things, help modernize and acculturate rural areas. The challenge was how to reach these areas, many of which received few or no radio signals in the mid-1930s. One solution was high-powered, clear-channel stations that could blanket large swaths of the country with a strong signal. These stations operated on “cleared” frequencies that the government assigned to only one station to prevent interference.

WLW had operated on one of forty designated clear channels since 1928. The station’s creator and owner, an entrepreneur, inventor, and manufacturer named Powel Crosley Jr. frequently increased the station’s wattage as technology and regulation allowed. In 1934, when WLW increased its power from 50 kW to 500 kW, all other clear-channel stations were operating at 50 kW or less. Now, WLW had the ability to reach most of the country, especially at night, when AM radio waves interact differently with the earth’s ionosphere and become “skywaves.” People living near the transmitter site often got better reception than they wanted; some lights would not turn off until WLW engineers helped rewire houses. Gutters rattled loose from buildings. A neon hotel sign near the transmitter never went dark. Farmers reported hearing WLW through their barbed-wire fences.

Continue reading…

Improving audio fidelity with JBL C2PS monitor speakers

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Last year at the W4DXCC conference in Sevierville, Tennessee, I spent some quality time with Bob Heil (K9EID). Bob is the mastermind behind Heil Sound as well as the host of HamNation, a show devoted to all aspects of amateur radio––yet this job description only scratches the surface of Bob’s fascinating career.

Bob Heil (K9EID, left) and yours truly (right) at the 2014 W4DXX conference in Sevierville, TN

One thing is for sure, however: there are few people in the radio industry who truly understand audio as profoundly as Bob Heil, so when he announced that he would host a forum at the W4DXCC to assist amateur radio operators in improving their received (and transmitted) audio, we were all ears, and signed right up.

Early in the forum, Bob described a set of self-powered and relatively affordable JBL monitor speakers that he highly recommended for amateur radio use. Everyone in the room noted the model number of the speakers, myself included. So imagine my dismay after the convention when I simply couldn’t find my notes…

Thankfully, my buddy Gary Wise (W8EEY) recently jogged my memory. Gary purchased a set of JBL monitors and matching wall-mount brackets from Amazon, and has them hooked up to his Flex Radio FLEX-6700 SDR. Gary tells me he’s very pleased with the set-up. Here are the links:

Bob also suggests adding a small mixer to system, something like this Behringer Xenyx 802 or the XENYX502 (both of which are on my current wishlist).

Bob invited me to speak on HamNation about shortwave radio. I may take him up on the offer…well, as soon as I overcome my videophobia, that is. At any rate, if you’ve not seen it, HamNation is certainly worth checking out. And in all things radio, Bob Heil’s is a name to know; click here to visit Heil Sound.