Many thanks to SWLing Post contributor Jeff McMahon for sharing a recent Herculodge post, where he battles radio frequency interference (RFI) while trying to enjoy his Tecsun PL-990—only to find his PL-880 unaffected. This led to a deeper reflection on FM listening habits and the temptation of tabletop radios like the Sangean HDR-18 and HDR-19. But with RFI always a threat, is a new radio the solution or just another problem in disguise?
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I recently bought a few new radios just to check things out after basically cutting back on my shortwave listening hobby in the late 1980s to get into personal computing. I kept listening but mostly through streaming shortwave broadcasts as I discovered my computer hobby and the growing prevalence of RFI from things like light-sensing outdoor lights, invisible fences, and cheap Chinese made electronics further increased the noise levels. When I recently switched on my radio, I heard perhaps three shortwave stations, all probably domestic except for Radio Havana. The rest of the dial, including WWV and CHU (which is not far from me here in western New York) were barely there.
Yes I need an external antenna most likely, but I recall listening to plenty of stations just using the attached antenna on my first shortwave radio – a Realistic DX-55 I got for Christmas in 1982. So it appears to be a combination of the ongoing trend to abandon shortwave broadcasting coupled with apparently very high noise levels. The old brick switching power supplies seem to be less of a factor now that many goods made overseas are powered by USB, and you supply your own USB charger, but those can be noisy too. Even the mediumwave dial was a mess of buzz. I’ll have to get my GE Superradio out and see if that is the case on that radio too.
I suppose the nostalgia of the much richer listening experience available in the 1980s is why today seems so discouraging. I’m not going to spend my time listening to conspiracy nutters and religious diatribes and even the robust days of the BBC World Service seem behind us, except perhaps for shows like Newshour. All of my favorites are essentially gone — RCI and RNW in particular, and what is left is a shadow of its former self. Even streaming is not an option for many stations that pulled the plug entirely on their English language sections. Shortwave to me is gliding towards a path that resembles Evan Doorbell’s Phone Trips analog phone switch tape collection — the complete end of an era.
I realize I am drifting from the topic like a bad radio going off frequency, but I guess the best radios out there treat streaming like another band on the dial. I just wish there were more external radio broadcasts, as opposed to listening to just domestic-focused radio, which is either not in English or sounds so corporately-programmed it doesn’t matter where it originates from.
Good post that re-visits the “scourge” of RFI.
This post triggered two “new thoughts” on RFI:
First Thought:
A.I. and “Large Language Machine Learning Models”
are a present day hot topic.
Could a few of today’s
A.I. Chat-bots
be fed information files containing:
a) the audio noises of an individual RFI source as heard on MW, FM and SW radio speakers
b) ID Label of device causing RFI info such as Manufacturer, Model Number, etc
c) or ideally – a spectrum monitor display file of this RFI showing amplitude versus frequency
This would create an internet version of the abilities of
“an old Ham Radio operator who has chased down RFI emitters for decades.”
Second Thought.
The Qodosen-286 portable has an auxiliary antenna 3.5 mm socket with both amplifier and attenuator.
If a “highly directional RFI sniffer antenna“
could be custom fabricated up to plug into the Qodosen aux antenna socket this might make for modern small and light RFI “foxhound” device.
My initial thought for such antenna would be a suitably enlarged
“Pringles Can WiFI antenna.”
Years ago after building WiFi Pringles can antennas
I built a 800 MHz Cell Phone Directional antenna
using a galvanized steel 35 gallon garbage can
and a commercial Wilson Electronics Co magnet mount 1/4 wave 800 Mhz antenna
which truck stops used to sell back then.
Another thought would be to copy the oldy but goody
“Ramsey Electronics Directional Antenna Kit”
that used a unique FM radio detection of “pulse phasing” from two dipoles at opposite ends of a horizontal cross bar.
In 1992 I used a Ramsey DF and an AOR AR3000 “DC to Daylight” scanner to find an annoying RFI emitter coming from a girl’s electric blanket’s ON/OFF switch at Duke U’s central campus apartments. The Ramsey DF antenna does not require that the dipoles be exactly at resonant frequency.
The ARRL RFI Book of year 1998 is
ISBN: 0-87259-683-4
Editor was Ed Hare, W1RFI
( note the insider’s joke by Ed of RFI in the call sign)
A public library would assign it a DDS number such as
621.38411 Am3513 1998
Bonjour pour les post publier sur mon fournisseur Internet je supprime ma boite Mail
Do you have RFI on AM be it Medium Frequency or High Frequency?
Switch mode power supplies RFI is worst at the AM Medium frequency decreasing with frequency. Thus the radiation becomes weaker as the frequency rises. It sounds like a power supply. Does the power supply for the good Tecsun have the same output voltage and maximum current. If so, what happens if you swap plugpack and see what happens.
If there is no interference to the AM bands the usual cause of this interference is microprocessors in computers, tablets and possibly phones. Often the data is blocked around 100 MHz which is in the FM band. Move them apart.
AM is a worse problem. I can get the powerhouse 640 but even that has a lot of noise. I’d like to try a premium AM radio to see if it could bypass the problem.
It is not the radio which is the problem, it is the power supply. The best supply is one which is a linear supply. That is one which contains an iron cored transformer (which makes it heavy and bulky) a rectifier to convert the low voltage AC into DC and a linear regulator using power transistors to act as variable resistors. This type cannot produce interference.
The power supply must be of the voltage specified for the receiver and a current greater than the receiver consumes. The plug must be wired the correct way around otherwise the radio can be damaged. (Some supplies come with the ability using plugs to swap polarity.