Category Archives: How To

Panasonic RF-1405: Mark seeks advice cleaning handle on thrift store find

Many thanks to SWLing Post contributor, Mark Hirst, who writes:

Going to a local UK charity shop will usually turn up a grim selection of romance novels, old DVD box sets and children’s toys. They do a brisk trade in clothing, shoes and bags, but technology often consists of dire examples of cheap DVD players, phone cases, and small TVs.

It’s those very occasional gems that keep me going back.

Last Sunday a Panasonic radio turned up, and being a canny eBay savvy charity, they put a proper price tag on it! Aside from a scratchy volume control which was easily sorted, it seems to work fine. Spanning the whole of shortwave on a single band selection makes for tricky use of the big tuning knob, but back in the eighties I suspect this wasn’t a problem.

Finger marks and general grime have cleaned up fine, but the handle is strangely marked, and after fruitless cleaning with cotton pads and a little water I’m wondering if this is some kind of oxidation below the shiny surface.

I’m wondering if other readers are familiar with this kind of problem?

What a great score at the thrift store, Mark! I have several receivers of the same era that have the same issue on their chrome/metal parts. It’s almost as if the chrome/metallic finish is pitted in some way.

Readers: Do you know how Mark could safely clean the marks off of the chrome finish on the handle of his RF-1405?

FYI, here’s a video of Mark’s RF-1405 tuned to CRI:

Mark, you certainly snagged a great radio at the thrift store!

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Tecsun PL-990: How to distinguish pilot run and final export versions

The Tecsun PL-990

As I suspected, it appears the Tecsun PL-990 batch that showed up recently on AliExpress for $399 each are the preliminary pilot run units that Tecsun offered in China last year. The final export version of the PL-990 is not ready for production yet and has been severely delayed by Covid-19 quarantines.

Anna at Anon-Co reports that Tecsun factories have been closed since mid-January 2020 and have only recently recommenced production, “but at a very slow pace.”

Since there will eventually be two different versions of the Tecsun PL-990 in the wild–the pilot run for China, and the finalized export version–I thought I’d share a trick Anna has described to tell the difference between the two.

Anna notes:

One way to easily see this is from the labels for the buttons above the keypad, these should be

[ TIME ], [ TIMER A ], and [ TIMER B ] (see picture below)

Tecsun PL-990 Final Export Version:

Tecsun PL-990 Final Export version

Tecsun PL-990 Final Export Version

Pilot Tecsun PL-990 (preliminary China domestic version):

Preliminary Pilot Tecsun PL-990 distributed in China — image from AliExpress.

Anna adds:

I highly recommend [no one] buy these pilot versions, because the software on those devices is also not developed.

There still isn’t a final version or any price indication available yet, but it will definitely not be US$399.99.

So in case it’s not clear: don’t purchase a PL-990 until you can confirm you’re receiving a final export version which has the TIME, TIMER A, and TIMER B labels.

Again, at time of posting, the final PL-990 export version is not yet in production.

When the final export PL-990 is available, I will announce it here on the SWLing Post with links to authorized retailers like Anon-Co.

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Airspy Youloop and Homebrew Passive Loop Antenna designs

Almost two weeks ago, at the 2020 Winter SWL Fest, I gave a presentation called “A New Era in Portable SDR DXing.

The presentation was essentially an in-depth version of an article I published in the January 2020 issue of The Spectrum Monitor magazine (see cover above).

I devoted a good portion of the presentation describing how to build a passive loop antenna design by Airspy’s engineer and president, Youssef Touil. This passive mag loop takes advantage of the Airspy HF+ Discovery‘s exceptionally high dynamic range and is an impressive performer.

The homebrew loop on the balcony of a hotel.

You may recall, I posted a short article about this loop in November after enjoying a little coastal DXing.

In short? This passive loop antenna pairs beautifully with the Airspy HF+ Discovery. I’ve also been very pleased with results using the new SDRplay RSPdx on the mediumwave band where the receiver now sports a high dynamic range mode.

Overdue corrections…

After returning from the Winter SWL Fest last week, I was hit with an upper respiratory bug. No doubt, a souvenir of my travels!  It wasn’t the flu (I was tested), nor COVID-19, but it did knock me off my feet for a few days with fever, coughing, and headaches. You might have noticed a lot less posts last week and almost no replies from me via email. I’m only now feeling totally human again and trying to catch up with my backlog.

Shortly after my SWL Fest presentation, I realized I made (at least!) two mistakes. I had planned to post corrections here on the SWLing Post last week, but the bug delayed all of that, so here you go:

#1 Schematic of my homebrew passive loop antenna

When Youssef started experimenting with passive loop antenna designs, he posted a few schematics of at least three build options.

Although I described how to build my passive loop antenna, I grabbed the wrong schematic for my presentation slides. Many thanks to those attendees who noticed this.

Here is the schematic I should have shared:

Note that the transformer has four turns on both sides (the one in the presentation had 4:2).

Again, apologies for any confusion.

#2 The Airspy Youloop passive loop antenna

If you’re not inclined to build your own passive loop antenna per the diagram above, Airspy is planning to manufacture and sell a lightweight, high-performance loop of a similar design.

Prototype of the Airspy Youloop in the field (note bright blue cable jacket)

During the presentation, I called the future AirSpy antenna, the “Spytenna.” I was incorrect. (Turns out, I got this name from an early antenna schematic and somehow it stuck in my head!)

Airspy is calling their passive loop antenna the Youloop. Youssef posted the following note in the Airspy email discussion group:

We are currently arranging the shipping of the affordable passive version to Airspy.us and RTLSDR Blog.

Btw, It’s called “Youloop”

Many thanks to Richard Langley and a number of other readers who pointed this out last week.

I’ve had a prototype of the Youloop since November and brought it to the SWL Fest and presentation. It’s a quality antenna and incredibly compact when disassembled and rolled up.

When the Youloop is available to order, we’ll post links here on the SWLing Post.

More to come!

Once I catch up here at SWLing Post HQ, I plan to publish detailed construction photos of the homebrew loop antenna.

Many of you have questions about how to tap into the center conductor at the mid-point of the loop. These photos should help guide you.

Stay tuned!


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Radio Waves: Eugène Aisberg, Filter Design, ABC Workers Face Cuts, and Data via Web SDRs

Radio Waves:  Stories Making Waves in the World of Broadcasting 

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Paul, Marty, and Michael Bird for the following tips:

Eugène Aisberg, Radio Writer (OneTubeRadio.com)

After a wartime absence, the January 1946 issue of Radio Craft carried an article by writer Eugène Aisberg.  While that name might not be familiar to American readers, Aisberg was a prolific author in the early days of radio, and wrote some of the best treatises on radio for the popular audience.  He was fluent in French, Esperanto, German, Russian, and English.

Aisberg was born in Odessa, Ukraine, in 1905, and lived most of his life in France. He was the director of the French magazine Toute la Radio and a prolific author of a number of books. His most popular book, which is still in print, is La Radio? Mais c’est très simple (Radio? But It’s So Simple!)  The book, currently in its 29th edition, an extremely solid background covering all aspects of electronics, and is written in a popular, easy-to-read style. While the book was ultimately translated into several languages, it was apparently never published in English.[]

Filter Design Software (Nuts and Volts)

If you’ve ever lived close to an AM broadcast station, you probably experienced the phenomenon known as fundamental overload. It occurs when a receiving device is functioning entirely properly but unable to reject a strong signal. The receiver might be a wireless telephone, a scanner, or even a TV or radio receiver. The AM signal is completely legal but just too strong, disrupting the function of the receiver or overriding the desired programming.

[…]Hams often experience fundamental overload on the 160 meter band (1.8–2.0 MHz) which is adjacent to the AM broadcast (BC) band (550 kHz–1.7 MHz). Antennas for those frequencies pick up a lot of AM band RF, overloading the input circuits and creating distortion or false signals inside the receiver. The usual solution is to install a high-pass broadcast-reject filter at the receiver input, attenuating the unwanted AM signals below 1.6 MHz while passing the desired 160 meter signals with little attenuation.

So far, so good, but a filter that doesn’t attenuate signals very much above 1.8 MHz while attenuating them significantly in the adjacent broadcast band is not a simple thing to design. There are tables and equations, but they are tedious to work with. Practically, you’ll need to build the filter with standard-value components as well, and that will affect filter performance too. Sounds like a job for some filter design software, doesn’t it?

There are several filter design software packages ranging from simple calculators to sophisticated CAD programs. Luckily for hams and other experimenters, there are plenty of free or low-cost programs to try.[]

ABC workers face anxious wait over job, program cuts (The Age)

David Anderson did not mince words at a Senate Estimates hearing last October. “There will be job losses,” ABC’s managing director warned. “It’s not something I can quantify at this point in time. There’s still more work to be done.”

Towards the end of March, Anderson will reveal a five-year plan for the national broadcaster. To the frustration of staff, it’s unlikely to specify which parts of the organisation will bear the brunt of these cuts or how many workers they might lose.

Several senior sources spoke about the situation at ABC on the condition of anonymity, given sensitive funding negotiations are yet to be finalised.

“All these media reports claiming the redundancy numbers will be finalised in March are just wrong,” says one ABC executive. “What we need is some clarity [about long-term resourcing] from the government.”[]

Receiving Data With Web Based Shortwave Radios (Nuts and Volts)

Your computer and the Internet give you free access to over 100 web based shortwave receivers that you can use as if they were your own. Unfortunately, employing these radios to decode data transmissions can be very difficult or impossible — unless you know the secret. So, read on and we’ll guide you through the details of how to do it.

Web based shortwave radios are an amazing new implementation of software defined radios (SDR). These SDRs are free to use and widely available on the Internet. Even more remarkable is that they are located in countries all around the world.[]


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Rescuing the Eton E1 from a sticky situation

I’m back from a week of travels and the 2020 Winter SWL Fest. In short, is was another amazing Fest and so much fun. I hope to write more about it in the coming days, when I have a few moments to catch up and after I shake a nasty bug (chest cold) I picked up.

Although I had no intention of making purchases at the Fest beyond a few raffle tickets, I couldn’t resist snagging an Eton E1 (XM version) at a silent auction from the estate of our recently-departed friend, Tony Pazzola (WB2BEJ). Tim Moody kindly organized the silent auction.

Tony was an amazing friend to all and an avid radio collector, so there were some excellent radios offered up in the silent auction–I could have easily easy bid on each and every one of them! In the end, though, only one really caught my eye: the Eton E1 XM.

A small sampling of the radios from Tony’s estate.

Tony took amazing care of his radios, but his Eton E1 XM suffered from what all of those models eventually do: a sticky chassis.

Back in the day (roughly 2009 to 2013) Eton/Grundig covared a number of their radios models with a rubberized coating that unfortunately breaks down over time and becomes tacky or sticky to the touch.

I think this E1’s sticky coating put off potential bidders.

It was particularly nasty–if you picked up the radio, you had to immediately wash your hands.

The E1’s starting bid on Friday was $200–quite fair considering this unit is fully-functional and comes with all software, cables, manuals and a SiriusXM radio antenna. By Saturday, the starting bid had been decreased to $150. I resisted putting in an offer, but after seeing that it didn’t sell after all bidding had ended, I couldn’t resist. That E1 needed a good home, right? Plus the proceeds go to Tony’s family.

The sticky coating didn’t scare me. If you’ve been an SWLing Post reader for long, you’ve no doubt read our numerous posts about cleaning off this mess. There are a number of solutions, but I’ve heard the most positive long-term results by employing a de-greasing product called Purple Power (click here to read archived posts). Indeed, it’s the solution Eton Corporation recommends.

On the way home Monday, I stopped by a big box store and grabbed a bottle of Purple Power.

Tony still had the original plastic film on the large backlit display.

Sporting a pair of nitrile gloves, I grabbed a bunch of paper towels and a few cotton swabs, then started the cleaning process. I spent the better part of an hour carefully going over the entire body of the E1and trying to remove residue in every crevice without allowing the Purple Power solution to creep under buttons.

In short?  I’m very pleased with the results and am now a solid believer in Purple Power.

As others have reported, Purple Power breaks down the sticky residue and allows it to be removed with a cloth or towels with very little scrubbing. Indeed, the process was much easier than I anticipate.

Now I have a super-clean Eton E1 XM to put on the air!

Now I have no excuse to finally remove the sticky residue from both my Grundig G6 and G3!

So far, I’m loving the Eton E1. It is, no doubt, a benchmark portable. Of course, another motivation behind snagging this E1 is so that I can compare it with the Eton Elite Satellit once it eventually hits the market.

Do you have an Eton E1?  What are your thoughts about this receiver? Please comment!


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Guest Post: Radiofreunde NRW’s DXpedition-grade signal distribution system


Many thanks to SWLing Post contributor, Joachim von Geisau (DH4JG), for the following guest post:


Signal distribution at SWL camps: The new JK-1000 HF distributor

by Joachim von Geisau (DH4JG)

The Friends of Radio NRW – an independent group of shortwave listeners and radio amateurs in Germany – have been organizing 2-3 SWL camps per year for a number of years, where they meet as far away as possible from electrical noise in order to listen to shortwave together.

To distribute antenna signals, we have previously used an RFT AVV01 antenna distributor.

At an SWL camp there are high demands on signal distribution. Both very weak and strong signals should be distributed well, un-distorted, without noise and other interference. The signal levels are approximately between 0.2 ?V (S1) to over 5 mV (S9 + 40 dB), with a frequency range of at least from 150 kHz to 30 MHz, thus broadcast bands from LW to SW are covered, also all amateur radio bands from 160 m to 10 m.

Popular among listeners are RFT AVV01 RF distributors from the former GDR, at least 30 years old. However, the use of an AVV01 has several disadvantages: high power consumption, difficulties in getting spare parts, high upkeep with corroded contacts and the like. In addition, the transmission of the LW/MW range drops, which is a disadvantage especially for MW listeners. The NV-14 system from Rohde & Schwarz from the late 1960s has the same weaknesses.

Two years ago, the desire arose to develop a concept for the replacement of the RFT system.
The following aspects were important:

  • Frequency range at least 100 kHz – 30 MHz, as linear as possible
  • frequencies below or above desirable
  • Running on 12 V DC or integrated noise-free power supply
  • Remote power supply for active antennas
  • Robust structure
  • Versatility
  • Hobby friendly budget

The amateur radio market offers several products for RF signal distribution (e.g., ELAD, Bonito et al.), but no solution to distribute 6-8 antennas to 10-12 receivers. It was clear from the beginning that DIY development was inevitable.

The starting point of the considerations was to integrate remote power supply for active antennas, an amplifier stage and a distribution network.

Such a distributor is able to distribute an antenna signal to several receivers; several antennas require several such distributors, which led to the decision to implement the project in plug-in technology.

With OM Frank Wornast DD3ZE (www.dd3ze.de), known e.g. for his converters, filters and the like, a well-known RF developer could be won, who took over the implementation of the concept based on the detailed specifications. OM Wornast first produced a prototype without remote power supply, which already did an excellent job of RF signal distribution.

A “hardness test” at an SWL camp showed that this distribution module easily fulfilled our requirements: Frequency range 10 kHz – 50 MHz (also usable with a few dB loss above 50 MHz). Supplemented by a switchable remote power supply and a 90V gas discharger at the antenna socket, the final PCB layout was created, representing the core of the new HF distribution system of Radio Freunde NRW

The distribution block consists of the following components:

  • Input with 90V arrester & 100 kOhm MOX resistor to dissipate static interference
  • Remote power supply, switchable, 10-14 V, max. 350 mA
  • Amplifier stage with 14-14.5 dB
  • Resistor network for distribution

The device is characterized by a very smooth frequency response and has a very low inherent noise. It offers the possibility of using levels of -120dBm with very good SNR
to process up to strong levels of up to + 14dBm. In addition, the reception on VLF is now possible, which did not work with the previous system.

 

The PCB is designed in a very practical way: series resistors for LEDs are integrated as well as fixing points for coaxial cables. The remote power supply can be switched separately, but can also be used permanently by means of a jumper.

With this concept, the distribution block can be used universally: use on an active or passive antenna with distribution to several receivers, by means of a step switch in front of it also for several antennas; if you leave the remote feed path unconnected, the block can also be used as a simple distributor, so it is almost universal for hobby purposes.

For use on SWL camps, we decided to install them in 19 “rack-mount technology. A standard rack can thus accommodate 4 distributors and a power supply, allowing  distribution of 4 antennas to 12 outputs each. An example of the installation is shown in the following picture: Parallel to the input is another BNC socket, which is connected via a C 100 nF where the input signal can be used DC-free for measurement purposes or the like. The distribution unit is installed in a transport case. The components themselves are mounted in slide-in housings which are provided with a corresponding front panel: Such front panels might be obtained from CNC manufacturers.

On the back + 12V DC must be supplied as operating voltage. For the power supply units, we opted for linear power supplies because we have made the best experience with these without interference. For a distribution unit with 4 slots, a power supply with 12V 1A is sufficient – each distribution block takes about 55 mA, an active antenna up to 150 mA, so even with “full load” a power supply with 1 A is sufficient. The distributor was tested with various well-known active and passive antennas, including a PA0RDT MiniWhip, active loops, long wires and T2FD.

Due to the wide input voltage range, the module can handle nearly any antenna. The cost for a distributor for 4 antennas amounts  (depending on the version: housing, sockets, switches, power supply, etc.) to about 700-1000 €. That may seem a lot at first glance. However, taking into account that a simple 5-gang distributor from mass production costs already around 250 ¬, the cost of the distribution of 4 antennas to each up to 12 outputs are not that much. The Friends of Radio NRW use two of these distribution units for SWL camps.

If you are interested in building one, please contact the author (dh4jg@darc.de) for further information. The development history of the distribution unit is also available at www.dx-unlimited.eu.


Wow!  What a beautifully engineered antenna distribution solution, Joachim!  I love how you worked together to sort out all of the requirements for your system then build it for ultimate performance and flexibility.  No doubt, you and your colleagues at  Radiofreunde NRW posses a lot of design and engineering skills!  Simply amazing and thank you for sharing your design with the radio community!

Contact Joachim for more details and check out notes and discussion at www.dx-unlimited.eu (may require registration).

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