Tag Archives: QRM

Selecting a budget antenna for urban radio listening


Yesterday, an SWLing Post reader contacted me with questions regarding budget antenna choices for an urban apartment. He’s about to purchase an SDR, but knows that a decent antenna capable of coping with urban radio interference is a critical component.

I suggested that, since I’m no expert with urban interference, he pose his question to the SWLing Post community. Here’s his reply and request:

I know I’m a little behind some of my other radio friends, but I’m finally moving up to a software defined radio. Specifically the affordability of the SDRplay RSP and all good reviews for it have encouraged me to make the leap.

The SDRplay RSP software defined radio

The SDRplay RSP software defined radio

I suppose it should go without saying that once I purchase an SDRplay I would like to use it, which might not be so easy. I live in a big city full of RF pollution, and most of my listening will be in a room where there’s a fair amount of electronic gadgetry.

So, without spending a lot of money, I’m curious if any of your readers might have suggestions about what I might purchase as a “starter kit” for a new SDR user in such a scenario. I also plan to take the SDRplay with me when I have forays out of the city, but I envision that some sort of long wire might be sufficient for listening out in the countryside.

I live on the second floor in an urban apartment, and have two windows in the room where I’ll be listening. There is zero chance that I can hang or attach anything on the outside of the house here. So, my most pressing question is about antenna ideas. I’ll need something inexpensive, as I mentioned, and something “off the shelf.” I don’t have the skills or tools to really “build” anything, unfortunately. So is there some less than pricy antenna or antennas I should look at? Or is there some hope of doing something with a long wire indoors?

Tecsun AN-100 portable loop antenna

Tecsun AN-100 portable loop antenna

And will my little Tecsun AN-100 AM loop antenna going to help me at all? I mostly plan to listen to MW and the HF bands, but I will inevitably check out signals far up the bands as well. So advise about listening to these bands is also of interest to me.

Other than that, I understand it’s important to attach the SDR to the laptop with a USB cable with ferrite chokes. And it probably wouldn’t hurt to buy some extra ferrite chokes to attach to other cables I might be using. I also plan to buy a NooElec mini-balun for use with a long wire antenna, and I already purchased a PowerMate USB knob because I still prefer to do my “tuning” that way.

So other than those basics my questions would be regarding connecting cables and adapters, and the best lengths of cable to use. Should I have some cable between the balun and SDR? I believe I’ve read that it’s better to have a longer USB cable and a shorter coax to the antenna, correct? And when it comes to using a wire antenna, are there preferences as far as what type or gauge of wire to use?

I am also interested in any general suggestions or tips from SDR users on getting started. In general, I’m pretty good with navigating through software, it’s usually the hardware issues that stump me. I’m looking to spend between $100 to $150 tops on everything besides the SDR, and I’d like to hear about peripherals, cables, adapters and connectors which when added all together won’t bust my bank.

I’m sure there’s plenty of people who read this wonderful blog who have plenty of useful knowledge regarding SDR listening on a budget. And I hope a few could share a little of their experience and collected wisdom on this topic here, for me and for others considering turning their computers into receivers…

Indeed. I appreciate this reader’s question, since many listeners live in environments with heavy radio interference. While we’ve published a number of posts touting the virtues of magnetic loop antennas, I don’t think we’ve ever looked for solutions at or below $150 US. While this may be a challenge, I’m also certain there are a number of readers who’ve found solutions to this problem.

So, Post readers, what might you do–or have you done–in similar circs?  Please feel free to comment, and let’s explore inventive and affordable solutions for this reader!

RFI from solar power installations


(Source: Southgate ARC)

The Netherlands national amateur radio society VERON reports on the pollution problems caused by Solar Panels installed on homes

Electrical systems such as solar panel installations must comply with EMC (Electro Magnetic Compatibility) standards. That means that there is a limit to the electromagnetic fields (EMF) that an electrical system, such as the combination solar panel and inverter including cabling, may emit.

However, a 2014 study in 14 European countries by the EMC Administrative Cooperation Working Group found this emission limit is more often than not exceeded.

Read the full story in Google English at


Guest Post: My Evolving, Morphing, SW Listening Station

Many thanks to SWLing Post contributor, TomL, for the following guest post:


My Evolving, Morphing, SW Listening Station

by TomL, May 26, 2016

My interest in radio listening has been rekindled after a long hiatus in parallel to my dwindling interest in Mainstream Media.  It is now about 8 years without cable TV and I seriously do not miss it, especially with the evolving nature of discovery with respect to other forms of media.  SWL radio was important to me in my formative years during the Cold War; fascinating were the many ways governments used shortwave radio to influence populations, each with their own brand of propaganda!  Young people today know nothing about the endless (and entertaining) tirades of East German editorial commentaries denouncing the evil, decadent West.  Or, of the free, large-sized envelopes full of travel and promotional brochures, pennants, bumper stickers, and booklets sent from the government broadcasters such as Poland, Hungary (yes, communist countries!), Australia, Netherlands, etc. just for sending in one simple QSL report!!!

I quickly realized that those days are gone forever, consigned to a period of history where radio was THE main method of disseminating copious amounts of government propaganda to very large swaths of humanity.  Now, the internet and cable TV fulfill that function in a much more CONTROLLED manner, both technically and socially (Big Brother like).  So, I have diversified my interests and have an unusual listening station.  It is multiple things in one small space.  You see, I live in a very small condo in a noise-plagued environment with only a 2nd floor wooden deck (owned by the Condo Association!) in which to put up any outside antennas.  Only a single “Dish” type antenna is allowed.  So my shortwave antenna needs to be well hidden.  Same for the TV antenna, since I also have a north-facing deck, I cannot have any line-of-sight to the Southern sky for a Dish.

The first wire antenna strung from the top and brought inside was a dismal failure receiving nothing but noise.  I gave up for a couple of years.  I built a loop TV antenna and mounted an FM antenna instead since those were less susceptible to noise issues.  Also recently added to this station are two cheap 4G antennas with wires into a single Verizon USB aircard plugged into my computer and getting up to 14 mbps performance.

But, I still wanted to try shortwave radio again (and medium wave too) but the noise issues were very, very discouraging.  S9 noise on some bands.  Tried preselector, a noise “phaser”, different lengths.  Nothing worked.  However, I read something from an amateur radio operator in Northern California who had a space problem.  He put up a helically-wound-vertical (HWV) antenna with radials for 160 meters (John Miller HWV antenna).  I also read about various “broomstick” antennas.  So, I tried my own version with an old RF Systems Magnetic Longwire Balun I still owned and NO radials.  Put it together with a 2 foot long, 4 inch schedule 40 PVC pipe wrapped in 200 feet of 18 awg magnet wire.  Well, still noisy but, at least now I had a portable antenna!

So, I went camping in March of this year!  Holy Cow, was it cold out but the helical antenna performed well enough to hear All India Radio for my very first time, a small 1kw Mexican station in the 49 meter band, and various others from Asia that were elusive for me in the distant past.  I was finally encouraged again to continue my research.  I did this a few more times and finally got tired of going camping just to listen to a radio!  NOISE at home was still the big bugaboo to kill (and it still is).

I read up on Common-mode noise travelling on ground and shield components of antenna systems.  So I bought a bunch of toroid ferrites of different types to cover different frequencies (something about initial permeability….) to make my own homemade “Super RF Choke” to cover all frequencies made on a Home Depot Homer bucket lid, winding the coax 5 or 6 times through all the toroids, the full diameter of the lid.

Measurements by Jim Brown published on the web (RFI-Ham.pdf), pages 32-33) indicate good choke performance using coax with these larger-sized coils.  I still hoped to salvage the use of the HWV antenna.  So, added the choke and noticed some improvement across most bands (less noise).  Medium wave broadcast was not effective and decided that I did not want to keep tuning an antenna that HAD to sit outside to get away from the noise inside my listening station.

I also shut off the power to my condo and found out which noise sources were mine vs. other noise that came from all the neighbors (very important step to do!!!).  For instance, I did not know before that USB charging adapters are PURE RF-NOISE EVIL in an innocently small package?!?!?!  I rearranged wiring to shut off certain devices and power strips when I want to listen to the radio!

So, I kept reading.  Found out about another magnetic balun from Palomar.  Tried it but not impressed –  performance was too lossy compared to the good old RF Systems MLB (what a great product that was back then!).  Kept reading and found out good things about the EF-SWL from PAR electronics (product is now made and sold by LNR).  The ground connections on it (and the Palomar) intrigued me.  So, I decided to go to Hamvention for the first time, even though I was skeptical of finding anything useful, I told myself, I could at least buy the EF-SWL on sale (which I did).

Installed EF-SWL to the HWV but no difference compared to the RF MLB. The antenna did perform better outside on the deck in the far corner, so there it still sits.  Then, I hooked up the wire they gave me with the EF-SWL to the ground and it resulted in MORE noise.  Then, took off the jumper (which connects the coax shield to the ground side of the balun) and connected only the middle post (balun ground) to the ground wire and a lot LESS noise resulted along with a small reduction in radio signal level!!!  Finally some progress – the wire seems to be acting like an old-fashioned “counterpoise”, which is misunderstood these days.  Apparently, back in the 1930’s-1950’s, people involved in radio knew the differences between an “earth ground”, a “radial system”, and a “counterpoise”.  Technically, they are all different and their use is different as a result.  Now, people moosh all these concepts together interchangeably which risks creating very ineffective antennas.

Photo of installed EF-SWL at the bottom of the HWV with coax at the output, the red magnet wire input on top, the middle post for the counterpoise wire, and the coax shield post is unused. 

Photo of installed EF-SWL at the bottom of the HWV with coax at the output, the red magnet wire input on top, the middle post for the counterpoise wire, and the coax shield post is unused.

The HWV antenna now has 600 feet of 26 awg teflon wire on the outside PVC, an inside 3 inch PVC “sleeve” with 102 Russian ferrite rods, a 56 inch stainless steel whip at the top, and one inch hole through the center to accommodate the 7 foot PVC mount to my carbon fiber photo tripod when I take it camping again.

So, I am on a new quest to understand counterpoises, how to actually TUNE them and, hopefully, how to use them to increase the performance of shortened antennas like my HWV (something about reducing the dB loss incurred by shortening….).  A second result I hope will be how to use the counterpoise to keep signal-to-noise ratio high at the same time (maybe with this used $100 Dentron Super Tuner bought at Hamvention?).


Also bought at Hamvention (thanks Thomas W. for the tip!!) and installed Bonito’s Galvanic Antenna Isolator GI300.

If input directly to the input of the radio, led to more reduction in noise and signal!!  Too much actually, so I took off my Super RF Choke and now I had a better result compared to the EF-SWL with the RF Choke (slightly cleaner sound with less hissy noise).  Apparently, the GI300 completely isolates the coax shield, better than my homemade choke!  The requirement is to use coax from the feedpoint and not bare wire.  I then placed a few clamp-on ferrites I bought from eBay to help with slightly higher frequency choking of the shield at various places on the feedline.


Photo of GI300 on radio with NO extra coax lead into the radio at right (Thanks to Dennis Walter of Bonito for that tip)

Before Hamvention, I wanted to try out AM broadcast.  I wanted to know more about this “FSL” antenna a well-known eccentric from Ireland (Graham Maynard FSL) developed before he passed away a few years later.  So read up and bought a whole bunch of ferrite rods and tried different configurations.  Well, my particular design did not work all that well because I did not follow directions for winding wire into a balanced design.  So, I added all those ferrite rods to the 2 foot HWV (inside a 3 inch thin-walled sewer PVC pipe).  The antenna is louder down to about 3 MHz with a stronger signal (including noise) than without.  I do not have measurements, and find it too time consuming to document.  Maybe one day, I will compare and document by sliding the ferrites out on the 3 inch PVC and measure actual signal levels.  The ferrite sleeve seemed to pick up MORE noise and radio signal than without it.  So, if you need more signal strength in a small package below 7 MHz, then the idea seems to have merit.  But since it increased noise as much as radio signals, it has limited usefulness to me.  I do have another project where I will put ferrite bars onto a tuned medium wave loop antenna (Tecsun AN100) that is much more portable and directional.  The bars and loop were both relatively inexpensive from eBay.  The ferrites change the tuning lower, so I have to figure out how to make it tune higher again…….

Photo of unfinished MW loop project.

Photo of unfinished MW loop project.


Evolving understanding of dealing with major problems like overwhelming noise and limited space have led to unexpected additions to my SW Listening Station:

  • A 2 foot long, 4 inch diameter helically-wound-vertical antenna (HWV) with way too much wire on it (and now inserted with 102 160mm Russian ferrite rods on a 3 inch diameter “sleeve”). Originally built because of its portability.  Can now be mounted on a carbon fiber photo tripod with a 7 foot 3/4” PVC pipe through the center length
  • A magnetic balun from LNR (designed by Parfitt) attached at the feedpoint of the antenna
  • A proprietary galvanic isolator from Bonito attached right at the radio’s antenna terminal
  • A “boat anchor” Dentron Super Tuner attached to the HWV feedline to help tune it
  • An unfinished MW loop antenna with more ferrite bars
  • An unused, homemade toroidal Super RF Choke
  • Clamp-on ferrites everywhere in proximity on wires and power leads
  • Re-arranged power strips and wires as needed for easier shutoff in functional groups

For shortwave, I still pick up mostly noise on many bands.  With the uncalibrated S-meter on the ICF-2010 – 49 meters is around S1 (before about S3).  31 meters is MUCH improved and is now listenable to stronger stations (S2 instead of S7 noise!).  Even 19 and 16 meters is improved from S6 to S7 down to about S3 now – noise still too annoyingly loud to understand any language being spoken however.  And forget about DXing from this location!  Will have to go camping again soon.

BUT, listening now to Voice of Greece, Radio Nacional Brasilia, or Radio Romania International is a much cleaner sounding experience than just a couple of months ago.  They are there to re-discover and appreciate, even though many speak a foreign language and I do not understand a word they are saying!  Also, there is the odd observation (like just this morning), that I can actually learn to enjoy listening to Country Music if it is the unique sounding Australian flavor!!

Do I miss cable TV??  Not a bit!!

Future investigations

  • Employ the Dentron Super Tuner in various configurations to find any improvements (currently attached to the coax of main feedline from the EF-SWL, it is helping tune different SW bands (not sure why it helps, does not make sense, must be a mismatch between coax and balun)
  • Obtain old book(s) on counterpoises
  • Get a Linear DC power supply for use with all the EVIL RF-spewing devices that use 5 volts. Maybe this one:  (Tekpower 3Amp Linear)
  • Replace any cheap/old RG58 cables with LMR-240 or similar
  • Finish the AM loop w/ferrites so I can take it places
  • Perhaps an ultra low-noise outdoor amplifier for the HWV, depends on counterpoise experiments: (Wellbrook ALA100M-2)  (I don’t want to spend that much money now)
  • Somehow use a noise antenna with a better phaser: (DX Engineering NCC-1) (gulp, don’t want to spend THAT much money now also!!!)
  • Get some relief from background noise using a really robust noise blanker. I don’t want to spend on the portable radio, would rather get something like the Bonito 1102S or an ELAD model both supposed to have excellent audio quality and excellent DSP noise blankers.  But that means getting a cheap laptop to run it and replacing the Sony.  MOAR big bucks…. but not right now
  • Maybe a real loop antenna, BUT it has to be remotely tunable and remotely turnable and small enough to HIDE. MOAR big bucks, sigh….

TomL from noisy Illinois, USA

Many thanks for sharing your experiences, Tom! Also, it was great meeting you at the Hamvention this year.

I must say that there is something to be said for brute-force experimentation when it comes to mitigating radio interference. I hope you keep us posted as you continue to experiment and improve upon your unique listening system.

Dave says not all Jameco power supplies are linear and regulated

Note that not all power supplies are listed as "regulated linear"

Note that not all power supplies are listed as “regulated linear”

Many thanks to SWLing Post contributor, Dave Zantow (N9EWO), who replies to a post published yesterday regarding some of Jameco linear power supplies. Dave writes:

“A bit of a caveat on Jameco’s these so called Linear power supplies. This is based from my own experiences so is not fiction.

Bottom of this page : http://www.jameco.com/Jameco/catalogs/c151/P92.pdf

Over the years some of (but not all) these Jameco linear regulated power supplies are no longer clean for radio use.

Without changing the model number or description of the product, they have made changes with some (or much of ??) this “Linear Regulated” adapter line. Indeed they are still using a good old power transformer, but when it comes to the regulator part of the adapter, they have gone to switching type regulator device. So it produces a nice strong whine on a radio receiver just as a full fledged switching supply.

I had purchased a number of these so called linear supplies (sorry I no longer have the exact model number noted that I ordered) and experienced awful interference with any radio receiver. So I cracked open one of these to see what was up here and sure enough it was using a MC34063A inverting switching regulator .

Called Jameco and they flat out denied that they were using any switching devices in this Regulated LINEAR Jameco ReliaPro adapter. So I then sent a nasty gram email to the CEO of Jameco. I received an email back (was from the CEO too) and after some research they FINALLY did admit a change was made in some of the product line to use of a switching regulator . But he strongly made the point they would continue to still market these adapters as totally linear (yeah right ….nice guys).

I must add here that it does (or did not) NOT affect the entire line of these linear regulated adapters. About a year ago I ordered more (already had a few before) of the 12 volt 1 AMP model 170245 , and these are (or were anyway) totally clean and are excellent.

Also note that Jameco purchases up surplus “linear regulated” adapters from time to time. This 6 volt 500 ma one here is an example and is (or was anyway) nice clean one and uses no switching regulators. Our 2 tested samples of this adapter from about 5 years ago used a nice 7806 analog regulator. Perfect for use with many SW portables, (including the Sony ICF-SW7600GR with a plug change). But a warning again from experience , they are all subject to changes without any warning (and this one may have changed too for all we know ??)

They appear to stick the ReliaPro name as the manufacture on all adapters (if it was made by Jameco or not)

So Caveat Emptor.”

Duly noted, Dave! I’ve also noted that not all of the power supplies on their linear power supply page are listed as being a linear supply (see screen grab at top of page).

I may contact Jameco about this too and see if they can adjust their search results to properly reflect a selection of regulated linear supplies.

How to replace a noisy wall power supply

JamecoWallPowerSupplyRegarding 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.


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.


Click here to read more about tip polarity. (Source: WikiPedia)

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.

TJamecoWallPowerSupplyip/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.