Category Archives: Portable Radio

Richard’s search to find the best SWLing spot on campus

SWLing Post contributor, Richard Langley, has been seeking the perfect spot on the campus of the University of New Brunswick (UNB) to listen to shortwave. He recently shared the following:

Here’s a link to a brief video of my recording of last weekend’s VOA Radiogram “in the field” (a UNB parking lot):

Richard goes on to say that he’s found an even better location:

“That location on campus (green pin on attached image) turned out to not be noise-free on all bands. Found an even better location (red pin). Negligible power-line interference although still within Wi-Fi range of UNB’s system but no significant effects from that discovered yet. Got excellent reception of VOA’s Radiogram this past Saturday afternoon. Extremely clean waterfall in Fldigi. And virtually noise-free images [below]”

Richard’s decoded message. (Click to enlarge)

VOA Radiogram decoded image

Many thanks for sharing this with us, Richard!

Those of you who live or work in areas with significant radio noise should consider scouting out a listening spot like Richard has. Also, you might be inspired by LondonShortwave who takes his radios to public parks. Regardless, moving your receiver as far away from sources of radio interference as possible will always yield better listening results.

Hamvention find: the Arvin 68R58 AM transistor radio

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Though I believe I spent more money at the Dayton Hamvention this year than I have in all previous years, I only purchased one radio: the Arvin 68R58 eight-transistor.

I spent a whopping $5 on the little Arvin in the Hamvention fleamarket. To be fair, the seller sold it for this modest price because he was not sure if the radio worked. But when I unsnapped the back leather cover, peered inside, and found the works remarkably clean, I suspected it might…

No original power supply was included, of course, and I was a bit concerned when I saw the somewhat out-of-character plastic battery holder. In the filtered fleamarket light, it appeared to me as if it required proprietary batteries–the holder appeared too small for C cells, and too large for AAs. There was no indication of the type of batteries it used, but since the spec read “6 volts,” I knew I could build a small AA battery holder, if need be.

So, at $5 (I bargained him down from $10, based on the doubt of operation) it was a very low risk purchase, and a potentially a fun project.

Back at home, I popped open the battery holder and looked inside…And I discovered the Arvin did, indeed, take four C cells. Simple enough! After inserting fresh batteries, I turned on the radio via the tone pot, and instantly heard beautiful, rich audio.

What I thought would be a project radio ended up being fully functional, and was, moreover, in tip-top shape.

So far, I’ve been very impressed with the Arvin’s AM sensitivity and audio fidelity. No doubt the generous ferrite rod antenna is doing the trick on medium wave.

Last night, as I tuned through the AM broadcast band, I was able to null out unwanted stations and noise amazingly well. There is something to be said of transistor radios from this era–let’s just say, they’re classics.

The Arvin has a simple set of controls: tone, tuning, and volume. There are no filter selections, of course, but I can tell that it’s quite wide; perhaps 8 or 9 kHz.

All in all, I’m very pleased with my little purchase, and the Arvin has become my new (vintage) bedside radio. Last night, I tuned in one of my favorite AM stations on 740 kHz, CFZM in Toronto, Canada. CFZM (a.k.a. “Zoomer Radio”) is not only a benchmark, but a right of passage for any worthy AM radio in my household. The Arvin passed the Zoomer test with colors flying.

And, yes, it even soothed me to sleep.

Now I only need to properly clean and restore the Arvin’s leather chassis and perhaps build a 6V-regulated linear power supply.

Next time you pass by a 1960s/70s vintage transistor, grab it! I’m certainly happy I did.

Now, I think I’ll turn on the Arvin, sip some dark beans, and put up my feet in the Pawley’s Island hammock…Cheers! Summer’s on the way.

Want one of your own? A quick search reveals that the Arvin 68R58 can be found on eBay for quite reasonable prices. Click here to search eBay for an Arvin.

How to replace a noisy wall power supply

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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.

Urban go-kit

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My good pal David Korchin (K2WNW) posted the above photo in his Facebook feed yesterday, simply titled, “Today’s carry.”

David is very much a kindred spirit; like me, he is constantly tweaking his go-gear. He works in New York City and likes to have his essentials with him there––radio included, of course. Since he’s a professional photographer, he never leaves home without the Lumix GF1 + Leica 20MM, very nice gear. Since he’s a ham and an avid ARES guy, he carries a Motorola XPR7550 UHF transceiver. And since he’s a radio listener, he carries the CC Pocket AM/FM radio.

True, he doesn’t have a shortwave radio in this kit, but he certainly takes his shortwave with him when traveling any further afield. Indeed, we once did some field work in Belize for ETOW and enjoyed a great SWLing session with the our Grundig G series receivers. Made for great comparison.

What’s in your kit?

Someday soon, I’ll take some photos of the kit that accompanies me most everywhere I go. In the meantime, we’d love to know what’s in your go-kit! If you have one, take a photo and add a few brief notes describing everything in it. I’ll post it here on the SWLing Post!

PS: For those who want to know, here’s David’s description of the above, in his own words:

“CLOCKWISE: Motorola XPR7550 UHF transceiver; Lumix GF1 + Leica 20MM; Moleskin folio notebook; Lamy Safari fountain pen; vintage Zippo lighter; Mercator lock blade penknife; CCrane Pocket radio; Sony El Cheapo™ earbuds; Luminox ANU Watch; iPhone; CENTER handmade leather card case from YXE, because Canada.”

Brilliant…! Thanks, DK!

London Shortwave updates his portable SDR

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SWLing Post contributor, London Shortwave, has updated his portable SDR setup to achieve a lower noise floor by implementing a Wellbrook UMB130 balun.

Click here to read his post.

How Bob found his Zenith “Bomber”

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After posting a link to Paul Litwinovich’s Zenith Transoceanic article, SWLing Post reader, Bob LaRose (W6ACU) sent me the following message:

“Just a quick story to follow-up on the excellent Zenith Transoceanic article today. It brought back a lot of great memories!

About twenty years ago I decided to collect some of the things that I couldn’t afford when growing up. I acquired quite a number of Hallicrafters receivers and other “heavy metal” including several transmitters (including my Viking I AM Transmitter). In the process of our last move, I got rid of a lot of the collection. One part of the collection that I did keep was my Transoceanics. If I remember correctly I have every major model except the military one mentioned in the article and the very last one.

Here is my story is about obtaining a “Bomber” as described in the article. I was visiting a gun show at the North Carolina Fair grounds in Raleigh (I went there with a friend who is into Civil War collectables). Anyway, we were walking around and I spotted a small dusty suitcase on a table in the back of a booth. It was closed and to anyone else it looked like an old carrying case. However, by the size and the brown leatherette-grained case I thought it just might be a “Bomber”.

I tried not to act too excited and asked the seller what it was. He said it was an old radio and I asked him to bring it out. Sure enough, it was a Bomber! Still trying not to act too excited, I tried to let on that I didn’t know what is was and asked him if it worked. He said he didn’t know. I made a point of saying that it was missing the dial cover (but the pointer was there and unbent and the inside looked pretty clean and even had its “Wave Magnet”).

I asked him how much he wanted and he said $100. We haggled a bit over the condition and I finally got it for $75. I walked away very happy and excited!

I spent some time cleaning it up, de-oxing the contacts and then used a VARIAC to slowly bring up the voltage to reform the electrolytics. But guess what? IT CAME TO LIFE!

I was even able to get the Sam’s manual and do an alignment. I don’t recall that I had to change any electrical parts or tubes and I even found a guy that made a replacement dial cover! It’s not as shiny as the one in the article but it was sure a great find. It proudly sits on the bookshelves in my office along with the Zenith “Sailboat” AM receiver mentioned in the article and my other Transoceanics. I’ve attached a picture of the two side-by-side. [See photos above]”

Many thanks, Bob, for sharing your “barn find”–or should I say “gun show find”(?)– Zenith “Bomber.” What a great story. I’m glad it’s in the hands of someone who has restored it and can appreciate its history. Indeed, your story proves that you never know where you’re going to find a vintage radio deal.

An inexpensive Windows tablet for portable SDRs?

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I’ve never been a fan of tablet PCs. I have an old Android tablet that I occasionally use to watch Netflix and read eBooks, but when I want to interact with a computer, I typically want the convenience of a proper keyboard and the precision of a mouse or large track pad.

With that said, this year at the Winter SWL Fest, I was co-host of a forum called: “Time Travel, Teleportation & Spectrum Hoarding for the Contemporary DXer.” My good friend and co-host, Mark Fahey brought his Windows tablet PC and we used it to demonstrate how easily and effectively SDRs can be taken to the field and spectrum recordings can be reviewed practically anywhere. Indeed, Mark tunes through his spectrum recordings while taking the train to work! (How cool is that!?!)

This week, I reviewed a guest post about portable SDRs by London Shortwave; afterward, I decided that I must begin the search for a Windows tablet. Since I would only use this tablet for portable SDR work, I really want to keep it as affordable as possible ($200 US or less).

It appears to me that there are a few things that you must overcome in a portable SDR package including: mitigating internal noise produced by the tablet and accessories, and the ability to power the tablet and the SDR at the same time.

Windows Tablet Wishlist:

Inexpensive (less than $200)
Enough speed and memory to run SDR applications and record spectrum to an internal SD card or external portable drive
Separate USB and power ports or the ability to power both the tablet and SDR at the same time

My choices so far:

Readers: Your recommendations and advice are most welcome! Please comment especially if you have experience using tablet/SDR combos.