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Hi there, if like me, you live in an urban environment, chances are QRM is having a negative impact on the quality of the signals you’re receiving at home. The presence of electrical noise makes antenna choice very important, particuarly if you’re planning to spend more than a few £££s on something more sophisticated than a length of wire. Recently I was considering the the purchase of a second compact antenna, for use at home in my shack and out and about on DXpeditions. I already had the excellent Wellbrook ALA1530 H field antenna, but at more than £250, it’s very costly and thus it seemed rather extravagent to buy a second one, if I could find something with similar performance for less expense. Space is at a premium at home and of course I take much of my equipment out on DXpeditions, so the Bonito Boni whip active antenna appeared to be an ideal choice. A wideband active antenna (from 20 kHz to 300 MHz) operating from 12 to 15V DC, with a very compact form-factor definitely ticked all the boxes. Furthermore, with reasonable second and third order intercept points of +55 and +32.5 dBm respectively, the Boni whip, on paper at least, looked like a pretty good buy at around £100.
Now, clearly, an E field antenna such as the Boni whip is not going to match the SNR provided by the H field Wellbrook ALA1530 in a noisy, urban environment. I have uploaded a few reception videos to my YouTube channel to demonstrate this, making a direct comparison of the two. However, what about the performance of the whip versus a simple longwire in an urban environment? Is there a delta in performance? The value proposition of the whip is primarliy in it’s performance, coupled with portability I suppose, but that must be considered a secondary requirement. The whip might be 10 or 15 times more expensive than a reel of cheap equipment wire, but will the reception justify the cost delta?!
Text links follow directly below, with embedded videos thereafter; you will find 3 reception videos comparing the whip and a 30 metre longwire, on shortwave and one each for LW and MW. At the end of each video there’s a section with the Wellbrook loop, just to calibrate where the longwire and whip are in terms of a much more effective H field antenna. The result? Well, there’s not much to separate the longwire and Boni whip, except on LW, where the whip prevails. A friend told me recently, if reception is rubbish at home under a blanket of QRM, don’t blame the antenna, the noise is the real problem. He was right. So, the next tests are to be undertaken out in the field, where the whip has a real chance to shine. I’m rooting for it because to have an antenna that performs as well as, or close to my loop out in the woods, yet can be packed away into a small case would be brilliant. Thanks for reading/watching/listening.
Clint Gouveia is the author of this post and a regular contributor to the SWLing Post. Clint actively publishes videos of his shortwave radio excursions on his YouTube channel: Oxford Shortwave Log. Clint is based in Oxfordshire, England.
Dennis Walter, of Bonito Radio in Germany, has just posted an excellent article on his blog regarding the importance of quality coaxial cable to fight local radio interference.
On Christmas Eve morning, the electricity went off at our house and panic quickly spread among our younger guests.
First, the TV sets went dark. Then, the desktop computers began to die as UPS back up batteries failed. For a while, we were reassured by the sound of familiar alarms, but then suddenly, total silence. Could this be the end times? Is this the onslaught of the apocalypse?
Smart phones were quickly deployed and guests began calling each other from room to room. The panic began to subside when several millennials volunteered communal usage of their wireless data plans. The kingdom would be saved…crisis abated.
[…]As the younger generation huddled around the smart phones with data plans, I began to think of the outage as an opportunity to listen to AM Radio, so I went to my office and dusted off my old RCA SuperRadio III.
I couldn’t remember the last time I replaced the batteries but to my surprise, it came to life with its signature popcorn sound when I pushed its big silver button. “IT’S ALIVE” WOW…the AM band was extraordinarily quiet and responsive.
[…]I scanned across the dial from 610 AM to 1590 AM. All the stations were as clear as a bell. Then, I decided to press my luck. I tuned to KTSA 550 AM in San Antonio and then I moved the dial slightly to the right and heard KLVI 560 AM in Beaumont, Texas. Every station was booming in loud and clear.
I felt like a child with a new toy. I dialed up and down the band, experiencing the clear booming sound of AM Radio without any noise or interference. It was a feast for the senses. It was beautiful.
After a few minutes, one of my daughters walked in and asked about the source of my entertainment. I pointed to my SuperRadio and said joyfully, “listen”. She looked at the big black box and asked “How can you listen with the internet and electricity off?” I responded, “It’s my portable SuperRadio III.” Before I could explain further, she shrugged her shoulders, closed the door and went back upstairs, convinced that her Dad was conducting some sort of high tech experiment.
In a manner of speaking, her assumption was correct. I was listening to AM Radio in a big city without the interference of computers, wireless modems and an overloaded electrical grid. For the first time in my recent memory, the “Senior Radio Band” sounded beautiful. Sadly, my experiment ended with preordained results when the electric power was restored.[…]
Many thanks to SWLing Post contributor, TomL, for the following guest post:
“Car Shack” radio listening
by TomL
My car is an unusual place to listen to shortwave radio but has interesting possibilities. Due to the obscene noise at my home QTH, I decided that I must try something away from this unfortunate situation. So I took my homemade 14-inch loop antenna and outfitted the appropriate ancillary equipment with DC power packs. My trusty Sony ICF-2010 is the radio “vehicle” to “drive” this experiment (LOL). And, seriously, this is a way to show the public that it is not that hard to have a portable radio listening setup. Believe me, if I can do this, anyone can!
The basic ingredients are pictured here with some variations (see text):
Wellbrook amplifier powered by DC power pack of 10 eneloop AA batteries
KIWA Broadcast band (mediumwave) inline filter
Palstar preselector (active antenna) plugged into car cigarette lighter
Sony 2010 connected to a second DC power pack
Sony ICD PX333 digital recorder
Sennheiser earbuds
7 inch Samsung tablet and 4G MiFi device to do internet schedule lookups
Illustration SEQ “Illustration” 1: Car Shack in operation.
An important finding was that anything that has a cheap IC circuit to regulate and/or convert DC power can be extremely noisy! The pictured 16000 maH lithium brick would initially be quiet but after a while it would start spewing noise all over the bands. Power cycling it sometimes helped but I decided that it is too unpredictable. Also, converter cables that convert 5V to 12V for devices needing 12V also produce overwhelming amounts of noise. Even a small 5V USB converter plugged into the cigarette lighter makes a modest amount of ubiquitous noise. I am ditching the lithium power pack and converter cables and any cigarette lighter adapters!
So, the main radio power pack will use the internal Sony battery comparment consisting of nine 2700 maH NiMH AA’s inside three D-cell battery holders that can each hold 3 AA batteries in parallel. This boosts the capacity to around 8100 maH for a modest cost (I already have NiMH chargers and the 4.5V requirement is not too high for the batteries in question). Pictured are examples of a single D-cell AA holder of which I bought 12 and the silver-top Powerex 2700 maH AA’s from fleaBay. The total voltage is slightly low (3.6V) but the Sony 2010 still works at a slightly lower performance (received signals are slightly weaker). I run the Sony on Local sensitivity and crank up the Palstar active antenna to compensate.
In a further quest for clean, portable DC power without noisy IC chips, I have been researching lithium batteries and it is quite a large amount of work to sift through all the variables. The Palstar active antenna and the Wellbrook amplifier both use external connections of 12V, 2.1mm (+ tip) plugs. NiMH is not going to cut it, too many needed and getting too heavy. Amongst the variables are things like:
Using a proper charger and not leaving it unattended or it could burn down your house
Chinese fakes being sold by the zillions that look exactly like the real thing
Initial cost being higher than current NiMH
Avoiding 1.5V step down batteries with noisy step down converter built-in
Learning the new terminology for sizes: AA = 14500 = 14mm diameter & 50mm length
Learning the differences between type of lithium: Lithium, Li-ion, LiFePo4, IMR, etc.
The difference between protected vs. non-protected batteries
How to avoid discharging the batteries too much which could render them completely useless (not just usage but also NON-usage as well)
How to physically handle Lithium batteries to avoid shock and temperature extremes
Learning how to compare maH’s of lithium to NiMH batteries
Finding out that most top rated 14500 Li-ion batteries are too long to fit into AA battery holders without risking damage to the protection PCB mounted at the bottom of the battery
and the list goes on and on…..
Here are some of the web pages I read to try to understand this technology:
So, to cut to the chase, I have decided to order this one from XTARDirect because:
I can order from a USA distributor who orders from the factory in Shenzen China
The price is very reasonable for “protected” lithium ion batteries
They actually should fit into typical AA battery holders without damaging it
Illustration SEQ “Illustration” 2 XTAR 14500 800 maH Li-ion
They are not the highest rated in terms of capacity, load drain, amp surge ability, etc., but they seem to have enough positive statements from users that indicate it gets the job done. Since I don’t have the lithiums yet, I am using some temporary 10-cell AA holders with good old Eneloops – good enough for now. And I am buying this discontinued charger at a discount to recharge lithiums:
Illustration SEQ “Illustration” 3: Nitecore i4 original version
I will make two power packs made from these items pictured. The wire is fragile so I super glue the insulation directly to the DC power plug housing (avoiding getting any glue onto the bare wire inserted at the back). I will use three sets of lithiums (9 batteries) plus one set of Eneloop Pro’s (3 batteries) per power pack in the aforementioned parallel AA holders.
Illustration SEQ “Illustration” 6: 2.1mm x 5.5mm DC power plug.
Other items of note: The umbrella stand is optional since I found I like to move the antenna around and even tilt it to get slightly better directional signal. More importantly, I found that if I cut the Sony 2010 sensitivity from DX to Local, and then crank the Palstar preselector’s amplifier, I get a cleaner sound with less background noise. Also, the KIWA mediumwave filter is essential due to overloading.
One of my favorite stations is Radio Educacion (XEPPM) on 6185 kHz. A 1 kW station near the foot of Vulcan de Guadalupe in Mexico City, it is so weak that I almost never hear it and their wonderful selection of music representative of regional & cultural heritage. It is also 1675 miles distant according to Google Earth. Now, if I want to bother, I can go out and listen in my car at locations less noisy than home. So far, the safest places have been the parking deck at work (only two stories high) and the local grocery store parking lot. What I would really like is a very tall parking deck whose owners let me stay up on top long into the evening without harrassment (not sure I want to risk security personnel questioning me about the strange contraption and equipment – paranoia reigns these days)!
Sample of XEPPM, moderately good propagation from the work location:
Unexpected reception happens with this experiment. I mounted the antenna in the back, away from the engine and against the rear side window. Was traversing the local restaurant drive-through lane to get a hot dog, and turning the corner next to the long empty brick wall, the reception became dramatically stronger and clearer! Apparently, the brick wall blocked some interference as well as enhanced the signal coming from the Northeast. You can hear the effect starting at 25 seconds into the recording of RRI:
Also, not recorded from a previous evening at the grocery store location, 6135 kHz Radio Santa Cruz in central Bolivia, a 10 kW station playing Spanish rock music and a clear ID near the top of the hour.
More experiments to do, like
Mount the antenna as high I as dare with PVC pipe (too cold out now and I would rather not open any windows but I am itching to mount the umbrella stand and antenna on a 3 foot PVC pipe on the roof of the car, the increase in received signal strength is significant)
A bigger backpack to carry all this equipment away from the car
If Elon Musk has his way and builds the Gigafactory (and competitors follow suit), there could be many more experiments with lithium type batteries in the future
Perhaps get an SDR and cheap laptop computer to replace the Sony radio
PS: I found out that the three-AA battery holders do not make contact at the (+) tip of the XTAR lithium batteries I purchased. I just gently lifted up the contact inside the battery holder to allow it to reach the battery tip, that’s all that is needed. Whatever you do, do not put an extra piece of metal inside the battery holders! I accidentally damaged the outside skin of two of the batteries with a common piece of copper metal and the batteries immediately started to get HOT. I took them out as soon as I could and the batteries cooled down. So, don’t use any extra metal surface inside the battery holders; lithium batteries do not tolerate any kind of short circuit!
Cheers from Noizey Illinoiz,
TomL
Thank so much, Tom, for sharing your experiences and your ongoing experiments! Lately, I’ve been doing NPOTA activations with a portable loop antenna on top of my vehicle. I completely understand what you mean about getting strange looks from passers-by! We look forward to hearing about your future experiments fighting RFI.
The past few days, I have noticed higher than usual noise levels, generally on the lower frequencies, and particularly on the longwave band, including the 285-325 kHz DGPS band, where I run nightly SDR recordings, to later process the data and decode and detect DX DGPS stations using my Amalgamated DGPS app.
Thinking back to what new electronics devices have been added to the house, two came to mind, a new cable modem, and a new ethernet switch. The switch is up here in the shack, so it seemed to be a likely candidate. The switch is a D-Link DES-1008E 8-Port 10/100 Unmanaged Desktop Switch. It uses a mini USB port for power, using either the included AC adapter, or power from a USB port. When I installed it, I decided to not use the AC adapter, but rather a USB port on my UPS, figuring it was better to not add yet another potentially noisy switching power supply to the mix.
The test was easy, I just unplugged the power to the switch. Sure enough, the noise vanished. Great, the switch is a RFI generator. Or is it? As another test, I plugged it into a port on a USB hub. No noise. Hmm… so it seems that the noise is indeed from the USB port on the UPS. I did not notice any increase in the noise floor when I got the UPS a few months ago, but It’s something I should look into again, just to be sure. The UPS is a CyberPower CP1350PFCLCD.
Here’s a waterfall from the SDR, showing the DGPS band, 280-330 kHz. You can see where I changed the power to the switch from the UPS USB port to the USB hub, the bottom part of the waterfall is when the switch was still powered by the UPS (click to enlarge it):
I still have a noise source just above 305 kHz to hunt down.
Update
I decided to see what I could do to improve things, and reduce the noise floor.
Here is the baseline, after no longer powering the switch from the UPS:
First, I relocated the AFE822 away from the computer and rats nest of assorted cables behind it, powered from an HTC USB charger:
The squiggly noise around 305 kHz vanished!
I then switched to an Apple USB charger / power supply, as their products tend to be a bit better made:
Another improvement, the overall noise floor is a bit less now.
But can we do better? I then switched to an older USB hub for power to the AFE822, that I thought might be better filtered:
I then changed to a linear supply plugged directly into the AFE822. I don’t notice any obvious improvement? Maybe it even looks like a little more noise? Difficult to tell. You can see a DGPS station popped up on 304 kHz while I was switching things around, between the last two tests, it was likely Mequon, WI.
Thank you for sharing this, Chris! I find a wideband spectrum/waterfall to be such a useful tool for tracking down sources of noise. Not only can you “see” the noise, but you can measure its bandwidth and identify what portions of the dial it affects.
In a previous guest post, SWLing Post contributor TomL, shared his “Evolving, Morphing, SW Listening Station” where he detailed the many ways he’s trying to fight heavy radio interference at his listening post. The following post is TomL’s update:
More Anti-Noise Ideas
(Continuing the hunt for better reception in a foul RFI environment)
by TomL
I have made the following changes:
Created a prototype mini-loop based on a crossed-parallel idea from VE1ZAC (Jeff).
Added 2 preselectors, an old Grove TUN-3 connected to the main loop feed and an MFJ-1046 connected to the ground connection of the balun. Both feeds go into the MFJ-1026.
Added a medium wave noise canceling unit that I have not figured out how to use yet. (Quantum Phaser). The MFJ unit does not work on medium wave without modification.
Purchased from eBay a used Grundig Satellit 800, a somewhat more robust fixed-station receiver to replace my aging Sony ICF-2010.
Other non-related (not shown): Whistler digital scanner + UHF over-the-air TV + FM broadcasts + an AM/FM HD digital radio + high pass filters from MiniCircuits.com – (audio from all these sources is passed to an existing high fidelity stereo power amp and NHT Super One speakers on the computer desk for near-field monitoring). Associated antennas are also hidden on the outside deck (shhhhh!).
Large charge card balance!!
So, here are some pics for the crossed-parallel loop. VE1ZAC web site has all the references if you want to explore further or google him. Mine is purely a prototype and not finished. And should eventually be placed on a rotor (but how to keep my Nazi-like condo association from finding out?!?!?!?).
It is three 14 inch quilters hoops from Joann Stores plus some 1-inch copper strips cut from a small 2 meter roll of thin copper from eBay. Then, it is wired in parallel with silver-plated aviation wire on each side with a feed in the middle. Not an optimal placement of the feed, (should go straight down along the pipe). Will fix things up whenever I get some more time.
Seems to be an efficient way to prototype small loops. It is now mounted on a short ¾” inside diameter PVC pipe into a cheap plastic sand-filled deck-umbrella stand. Loops are light and somewhat flimsy, so I mounted the three loops on a plastic triangle ruler and dowel sticks glued to the sides for some extra strength. Good enough for now.
The EF-SWL balun is also in an experimental configuration. Since I read somewhere that loop antennas have a very low impedance at the feed point (like, 10 ohms or lower), I thought I might try a balun that is meant to lower the impedance and mount it backwards. I don’t have a picture of it but the SO-239 output is facing the loop and the screw terminals are facing the direction of the radio. My feeble brain thinks since it is a passive device of coils on ferrite, it should work bidirectionally for receive only applications like this. It seems to work but I have the excuse that I really don’t know what I am doing! 🙂
BHI unit in action.
The BHI DSP filter is useful in some circumstances but I find it fatiguing to listen to. The audio from the Sattelit 800 is so nice, I mostly like it without the DSP. The DSP narrows the bandwidth significantly, somewhere around 4 kHz or less from my hearing. I like that the Grundig has two tone controls. And it also has a stable SSB and on very strong signals with clear audio, I like to listen with SSB lower or upper sideband. But the DSP is useful at times for hash-like noisy signals; it is not quite as good on buzzing noise and I wish the Satellit 800 had a noise blanker, but that would have been a more costly purchase, like a Drake R8A.
So, in a nutshell, I have a discovery about noise here: it is all around me and ubiquitous, like the air I breathe!
I find it hard to null and also worry about peaking a station signal at the same time. However, I do have a lower noise floor with the experimental loop sitting outdoors, especially on medium wave (the Wellbrook amp + loop works great on the lower frequencies – am able to get eight different medium wave stations carrying Major League Baseball games at night – it would be nine to get WFAN for the New York Mets but the local Chicago Cubs station covers the adjacent frequency with horrible digital hash! ***Bleeping*** digital junk!).
Also, the signal level is noticeably lower using the loop. Then, add in the effect of the MFJ Noise Canceling unit, the usable signal gets even weaker.
The bottom line is, I can now finally enjoy listening to many SW broadcasts, BUT only the strongest signals. Anything else is still hopelessly lost in the noise. So, gains are limited.
On the other hand, and something else I learned by doing is that, any 1 or 2 dB signal/noise ratio improvement will help with the final audio output in the end product. Using low-noise amps, loops, noise canceler, preselectors, grounded connections, ground isolators at the input of every receiver, high quality stereo amplifier and speakers, tone controls, SSB vs. AM Sync, weird antenna configurations, etc, etc. It all helps in the end to some degree.
Tinkering is an art that involves a lot of thinking/doing iterations! And high quality parts must be used all along the chain or it could degrade the signal.
Below are some audio samples, not very well recorded, but can give some idea of the incremental improvement with each enhancement (turn up the volume). NOTE: other people may get better or worse results depending upon individual situations, type of antennas used, etc, etc.
Recording 1: R. Marti. First 10 seconds an indoor antenna with no noise reduction, second 10 seconds the outdoor loop without the MFJ-1026, the third 10 seconds with the MFJ-1026, then switched off and on to hear the difference.
Recording 2: R. Marti. MFJ -1026 is ON. Last 15 seconds is SSB, very thin sounding. Really only good for strongest signals. I liked the AM Sync better (Satellit 800 is really a Drake SW8 in disguise with a quality AM Sync). But, SSB can sound excellent with very clear voices with a steady and strong signal (The Satellit 800 does NOT have IF-shift or a BFO to fine tune an SSB reception, so the station must be exactly transmitting on the kHz mark, which most are nowadays).
Recording 3: R. Marti. MFJ-1026 is ON. Last 20 seconds you hear me switch in the two audio switches and the BHI DSP is on its lowest setting. Narrower and clearer with some reduction of background noise. I find I only like going up to about 4 on the DSP dial, after that the audio fidelity starts getting more choppy with digital artifacts that sound like dripping water. I tend to like higher fidelity. One nice thing about the BHI DSP is a faux-stereo that helps a little with voice intelligibility by helping the brain naturally filter the noise. Faux-stereo is ON even when the noise reduction circuit is manually turned off (power must be on and bandwidth still sounds narrowed).
Recording 4: R. Nacional Brazilia. First without MFJ-1026, then ON, then OFF, then ON, then with the BHI kicked for the last 20 seconds.
Recording 5: Greece. Switching the MFJ-1026 on and off every 5 seconds. In this particular case, the signal was weak and fading a lot. The MFJ OFF was also weaker than with it turned ON. That is interesting behavior, usually it is opposite. It pays to play with the settings a little. At other times, and less frequently, the MFJ unit turned OFF sometimes sounds better than with it ON and tuned for less noise. Go figure!
After all the tweaking is done, and I cannot get any more performance out of this, I will probably have to move to a nice, quiet neighborhood and setup a nice antenna farm!!
In the meantime, I do enjoy listening to the stronger stations from North America, Cuba, Brazil, Europe, and Australia with less noise than before.
73’s
TomL from NOIZEY Illinoiz
Once again, Tom, thanks for sharing your RFI elimination journey!
I love how you take on this noisy problem by experimenting and seeing it more as a challenge than an obstacle to enjoying your hobby. Great job!
Many thanks to SWLing Post contributor, DanH, who writes:
I read this news item today. AT&T has a new approach to broadband over power lines called AirGig. Supposedly, this technology will avoid RFI issues encountered with previous BPL technologies. This shouldn’t be an issue in my neighborhood where power lines are underground. Underground utilities still have RFI issues. My next door neighbor’s AT&T high speed internet swamps out all nearly all shortwave signals below 4.7 MHz within radius of 30 feet from the connection box.
d compact antenna, for use at home in my shack and out and about on DXpeditions. I already had the excellent Wellbrook ALA1530 H field antenna, but at more than £250, it’s very costly and thus it seemed rather extravagent to buy a second one, if I could find something with similar performance for less expense. Space is at a premium at home and of course I take much of my equipment out on DXpeditions, so the Bonito Boni whip active antenna appeared to be an ideal choice. A wideband active antenna (from 20 kHz to 300 MHz) operating from 12 to 15V DC, with a very compact form-factor definitely ticked all the boxes. Furthermore, with reasonable second and third order intercept points of +55 and +32.5 dBm respectively, the Boni whip, on paper at least, looked like a pretty good buy at around £100.
