Tag Archives: Emilio Ruiz

Post-storm power outage leads Emilio to find the RFI-spewing source of his problems

Storm with lighteningMany thanks to SWling Post contributor, Emilio Ruiz, who shares the following guest post:


Apprehending an RFI-generating monster!

At the beginning of the year, I was sad because, at home, an awful RFI noise appeared. The next few months the noise increase until S9!!. Day and night my receivers and my feelings were so dampened with this terrific RFI–only the lower Broadcast Band (900 to 540 Khz) was relatively immune to it.

Yesterday, we had a storm and the mains electricity service went off, so I connect a 12 volt battery to my RT-749b military surplus transceiver and the received signals were very clean like the “good old days”.

(Above: Listen W1AW loong distant from my QTH in Chiapas Mexico).

When the power electricity come back on, so did the RFI too!!

(Above: W1AW gone)

Remembering the recently publish post in SWLing Post about RFI, I did some testing by
cutting the electricity to my home (the main switch) and the RFI was gone!! So I discovered the RFI lives in my house–not in the outside wires!!

I put batteries in my old shortwave portable radio and searched (like Ghostbusters) all outlets contacts, one by one, connect and disconnected each device.

And I found the guilty party!

Exhibit A: The Mitzu laptop power supply

On December 2019, the power supply of my son’s laptop broke, so I bought a cheap substitute.

The RFI produced by this little monster could be heard at a distance of about 200 meters from my QTH!!! (Much like an old transmitter spark gap–!)

Even this cheap power supply apparently featured ferrite toroids on the wire but turns out it is fake!! It was only a plastic ball!

Exhibit B: Fake toroids!

The wires were also not shielded. No doubt one of the worst switched-mode power supplies I could have purchased.

Exhibit C: The Mitzu RFI generator wire without shield, only pair wires!

I found a old Acer power supply with same specs and I replaced out the RFI monster one.

And now? The shortwave bands are clean again.

(Video: Testing my Kenwood R-600 rx with Radio Exterior de España… plugging and unplug the Mitzu monster RFI generator).

So I wanted to share what happened to me, so perhaps it can be useful for other SWLing Post blog friends.

Watch these little switched mode power supplies from all devices in your home. Replace them if you detect RFI levels that harms SWLing. Consider disconnect all devices (vampire consumption–or phantom loads) if not in use; the radio waves and electric bill will be grateful to you!


WOW! What a difference! Emilio, that was great investigative work on your part. It’s as if that switching power supply was specifically designed to create RFI! No shield and fake toroids? That’s just criminal in my world! 

Thank you so much for sharing your story. Hopefully, this might encourage others to investigate and apprehend their own local RFI monsters!

(And by the way, Emilio, I love that RT-749b military transceiver!)

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You’ve Been Warned: Emilio just brought a Grundig Frankenradio to life–!

Many thanks to SWLing Post contributor (and certified mad scientist), Emilio Ruiz, who writes:

Recently I was given a broken Grundig G8 Traveler II.  This radio had an accident–the case, speaker, tuning knob, and volume controls were all broken or damaged.

I discovered that the tuning and volume controls are not potentiometers, they are a rotary encoders, so I substituted the tiny and broken original controls with rotary encoders (typically used for Arduino projects), but I needed to remove the 10 kiloohms resistor to work properly (only used the CLK, DT, and GND pins).

All materials were reused from other things, the result is like a “Frankenstein radio”.

The “telescopic” antenna is a tape measure/flexometer which was broken too. I replaced the original speaker (which I think was another impedance) with a proper 8 ohms speaker which produced low volume, so i decide add a Pam8403 amplifier module for best performance. The total current drain is 0.10 amp for a regular “loud” audio level.

So the Grundig Frankie is alive!!… It’s alive!!

Click here to view video in new window.

This is brilliant, Emilio! Although this radio is quite scary–and, let’s face it, “post-apocalyptic”–I think it’s absolutely amazing! I love the handle and the tape measure antenna. You, sir, are a mad scientist and I look forward to your next creation! (I’ll just take shelter first!) 🙂

Anyone else ever created a Frankenradio? Please comment!

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Can you identify this radio from the 1992 film, ‘Sneakers’–?

Many thanks to SWLing Post contributor, Emilio Ruiz, who writes:

Hi Thomas,

I’m sending you and The SWLing Post readers these screenshots from the cult
movie Sneakers; a great movie about incipient world of hacker security
(phreaking, hacking, cryptography, etc).

In a scene with Robert Redford and Dan Aykroyd, it looks like a radio communications receiver in the background, but i don’t know what brand is.

Could you help for identification?

Great job spotting that radio in the background! Readers: please comment if you can help Emilio identify this rig!

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The Cat’s Whisker – 50 Years of Wireless Design

Many thanks to SWLing Post contributor, Emilio Ruiz, who notes:

Searching archive.org found this [compilation] book: 50 Years of Wireless Design (click to view on Archive.org)

Click here to download a PDF copy.

I hope it will be interesting for you and the readers of the blog.

[The attached] cartoon is very funny… How eliminate “the hand
capacity”:

Excellent find, Elilio! Thank you for sharing!

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Emilio’s favorite scene from “Never Cry Wolf”

Many thanks to SWLing Post contributor, Emilio Ruiz, who writes:

I [note you] have published movies scenes with radios and I remember one of my favorite movies about nature, science, silence, wolves and Inuit culture called “Never Cry Wolf” I’m sharing with you and all readers of SWLing Post blog a radio (I don’t know what brand is, I think is military radio) appear in Never Cry Wolf movie.

I love this scene because the heterodyne sound is a particular sound that drives us crazy to everyone who loves radio!! jaja 😛

The video was extracted from the original Beta format movie, sorry for
the quality.

Thank you for sharing, Emilio!

That heterodyne sound leads me to believe they obtained it using a regenerative receiver. I’ve heard that squeal so many times tuning regen receivers!

I’ll add this post to our ever growing archive of radios in film!

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AM receiver design with regards to IBOC bandwidth claims

Many thanks to SWLing Post contributor, Emilio Ruiz, who writes:

Hi Thomas,

I’m writing because found this (interesting) analysis about radio
components and the impact on radio receiver quality:

http://www.geocities.ws/shreddermanrulz/myth1.htm

I think may be are interesting topic for readers of the SWLing Post.

This is interesting, Emilio.  Thank you for sharing. Although the reason the author put together this post was to refute IBOC’s claims about testing AM receivers, it is also a fascinating look into cheap AM radio/receiver design.  Thank you for sharing!

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