Category Archives: How To

“Crystals Go To War”: A 1943 film about the production of Signal Corps radio crystals

Many thanks to SWLing Post contributor, Charlie (W4MEC), who shares this fascinating film which documents the production and calibration of crystals in 1943. I had no idea of the amount of labor and attention to detail this process required–an absolutely fascinating process:

Click here to view on YouTube.

Spread the radio love

An external battery pack for the Sony ICF-SW35?

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

Hi Thomas I enjoy reading your blog and often when I put a question in Google yours is the first on the list so I wonder if you’d mind if I ask you a question about the Sony SW35.

I’m interested to try powering it from a power bank but I have no idea what DC plug to buy for it as I bought it second-hand without an adaptor.

I thought about taking a couple of wires out of the battery compartment but it wouldn’t look as nice so any help you could give me would be much appreciated.

Great question, Adam!

You can certainly find a DC plug that will work with the ICF-SW35. I believe this same plug was used with a number of Sony Walkman type players back in the day. You might be able to find one at the local charity/thrift shop in their power cord jumble.

DC plug coaxial portI do know that the coaxial type plug needs to have positive tip polarity (click here to read about this in the owner’s manual) and the radio requires 4.5 VDC . The OEM power adapter (Model AC-E45HG) provided 700 mAh, but I don’t know what the ‘SW35 actually requires (other than something equal to or less than 700 mAh).

One option would be to find a 12VDC to 4.5 VDC converter like the Sony DCC-E345 and plug it into a 12VDC source (there are a number of high capacity 12V battery packs on the market).

Of course, you could also build your own external source by purchasing an appropriately sized external battery holder. I would use a D cell holder (I assume one to hold 3 cells at 1.5VDC x 3 = 4.5 VDC) which would provide much better capacity than a AA cell holder. (Something like this.)

I haven’t been able to determine the +/- voltage tolerance of the ICF-SW35, so I would keep the supply voltage figure at or below 4.5 volts.

One crucial number I’m missing is the coaxial plug size. I can’t seem to find a spec for OEM Sony AC-E45HG. I hope a reader might be able to help us here.

Post readers: Can anyone confirm the DC plug size for the Sony ICF-SW35?  If you have any other advice or tips for Adam, please comment!

Spread the radio love

Robert talks uBITX and navigating the world of used radio gear

Robert’s uBITX QRP transceiver kit with fire red chassis.

Many thanks to SWLing Post contributor, Robert Gulley (AK3Q), who shares the following announcement from his blog All Things Radio:

I have posted two new articles in the Reviews and How-Tos section. These were both previously published in The Spectrum Monitor magazine earlier this year.

The first article deals with buying used and new equipment, while the other article is a review of the uBITX QRP transceiver. Thanks go to Ken Reitz for graciously allowing these to be posted after their initial publication!

Many thanks for sharing, Robert!

Readers, I highly recommend both of these articles.  In his used equipment guide, Robert makes practical suggestions for navigating the world of pre-owned radio gear and shares some important tips. His uBITX QRP Transceiver article is essential reading for anyone who has considered building this incredibly affordable kit.

Spread the radio love

Stefano invites you to experiment with DRM (Digital Radio Mondiale) over IP

Photo by Sergi Kabrera on Unsplash

Many thanks to SWLing Post contributor, Stefano Mollo (VK6WFM), who writes:

I have been lately experimenting with DRM 30, with the aim of coming up with a cheap solution to get on air for next to no $$$, for small, local broadcasters that would either go pirate on FM or would not go at all due to the impossibility here in Australia to get a proper FM license at a cost that does not involves selling a kidney (or two)!

I am a ham radio operator, so I turned my attention to DRM30; [the DRM application] DReaM has the capability of acting as a transmitter as well, so I started experimenting.

Click here to download DReaM via SourceForge.

I was very successful at transmitting a DRM30 / 10 kHz signal with a $ 0.50 TX module otherwise intended to transmit data with an Arduino. The signal was received with an SDR + HDSDR + Virtual Audio Cable + DReaM in reception mode.

So far, so good; with this experiment I realised that DRM 30 can, in fact, yield excellent quality at ANY frequency (as I used the 433Mhz LIPD range in my experiment) or better said, with any medium, as long as it is linear enough to transport the DRM signal.

I wanted to find a way to show the World – literally – what can be achieved with DReaM in TX mode…for free!!!

So, after some trial and error, I have set up the system below which allows anyone in the World to “tune in” my “DRM30 radio station” and listen to my DRM30/18 kHz signal, in full blown stereo. Quality is exceptional, and just imagine to send DReaM’s signal to a proper transmitter instead of streaming it over the internet ….

So…point your VLC Media Player (on Windows) to stream from:

…then pipe VLC’s output to DReaM’s input via Audio Cable (or any other Virtual Audio Cable you like).

In DReaM, select the audio cable output as the sound card’s signal input device:

Then select L+R as Channel:

Set the sample rate to the highest value:

One more thing you need to set is the “Channel Estimation: Time Interpolation” parameter to Linear; this is very important!

After few seconds you should be able my test signal, in full stereo, streamed from a PC running DReaM in TX mode, whose output is then captured by MB Recaster and streamed to an ICE Cast server I have in the Cloud. Note that no particular configuration was needed on the ICE Cast server, at all.

This is an example of what can be achieved on a solid transmission channel with DRM30 and only 18 kHz bandwidth (i.e. the normal bandwidth of an AM channel).

One can achieve the same exact audio quality using any channel linear enough to transport an 18 kHz wide DRM30 signal. It doesn’t matter the frequency, or the physical medium per se.

[…]My aim with this experiment is not to send DRM over IP; there are much simpler ways or streaming audio over IP.

Rather, my aim is to demonstrate what can be achieved with 18 kHz +DRM30 on any frequency and on any medium (which, could be for example the electrical distribution overhead lines …. just saying …. 🙂 ).

If only the local regulator would support this, instead of enforcing draconian regulations … such as the restriction of just 6 kHz on shortwave.

Please share your thoughts.

Fascinating experiment, Stefano! Thanks for sharing!

Post readers: If you’re in the mood to do a little experiment, let us know if you’re able to decode Stefano’s 18 kHz DRM30 broadcast over IP!  Please comment!

Spread the radio love

Tommy (N1SPY) on monitoring airplane communications

Many thanks to SWLing Post contributor, Ivan (NO2CW), who writes:

If anyone is interested in monitoring aircraft communications across HF, VHF and UHF, Thomas, N1SPY put together a demo video of what you can hear and how:

Click here to view on YouTube.

Brilliant instructional video, Tommy! Like you, I love both radio and aviation so appreciate the effort you put behind this video.  Great primer!

Click here to check out other projects by N1SPY.

Spread the radio love