Many thanks to SWLing Post contributor, TomL, who writes:
Just a quick note to allow SWLing blog readers to check out a nice pair of lightweight ear buds to use for listening for only $14.99.
I found these on Amazon from a Marketplace seller getting rid of discontinued stock. They are headsets for iPhone but seem to work just fine in any radio I plugged them into. The voice quality is very slightly on the bright side, which seems to help with hearing voice, especially if you have chosen a narrower bandwidth. There is good bass response, perhaps too much for shortwave listening but one can easily just unseat each ear bud from your ear canal slightly until the excess bass is gone.
Most bad ratings are of people too impatient to notice that the right ear cable is longer than the left for a very good reason. The right side drapes around the back of your neck to help hold the ear buds in place and you plug it into your ear from behind. This is by design and it works well without having to clip it to anything like a moving shirt collar! Great idea, wish other manufacturers would do the same.
They are comfortable to wear for long times. Just used them over the long weekend for a couple hours at a time and never noticed them. They use Sennheiser’s rubbery and removable ear cups that come is three sizes. I left the Mediums on but the Small and Large are in the package if you want to experiment.
I have also used them to listen to radio reviews on YouTube and hear great depth and separation in the video depending on what kind of video recorder the reviewer used and can really hear what the radio sounds like. Very nice.
Finally, in a pinch, you can use these on your smartphone as a backup headset. The mic input hangs right below the left of your jaw.
Get them while they still have stock. There are white and black versions but no choice allowed. I ordered two (I keep misplacing my CX-475 Sennheiser ear buds!!!) and they are both the black version, which is fine by me. Enjoy!
Thank you TomL! I just purchased a pair. I use in-ear headphones every day. I use them to listen to the radio, to podcasts, and as hearing protection when I’m operating my lawn mower, chain saw and trimmer. (When using them with equipment, though, I tuck the cord underneath my shirt so no wires hang out to get snagged).
I keep a spare set of in-ear headphones in my EDC pouch.
I always have a pair in both my right pocket and in a pouch in my EDC bag. The ones in my EDC bag are Panasonic Ergofits and aren’t quite as good at sound isolation, but have decent audio and are very comfortable to wear while sleeping.
This is just a quick Field Update for my Backpack Shack 2.0 antenna. It is not the most powerful antenna but in the right location it can be useful, especially with using an SDR. It was used during February in two Forest Preserve (County Park) locations outdoors and once from my usual Grocery Store parking lot!
Please excuse some of the computer generated noises (caused by a slow CPU) as well as some audio connector problems on a couple of recordings.
Each Time is in UTC and Frequency in kHz. Where can you hear unique programming like these samples except Shortwave Radio??? Enjoy!
Many thanks to SWLing Post contributor, TomL, who writes:
Regarding the last couple of posts recently about what affects Space Weather (and HF radio communications), this talk last week from Solar scientist Joan Burkepile of the High Altitude Observatory discusses what causes Radiation storms from Coronal Mass Ejections. She makes it interesting from a physics point of view. And as we understand the sun better, we also learn more about how the rest of the universe behaves.
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Backpack Shack 2.0
by Tom Lebryk
Like Audiophile speakers, it could be said that “antennas are forever”. They tend to not become obsolete like all of our favorite electronic gear (a good one is worth the trouble). And antennas don’t care if the signals are digital or analog formats. They are “Digital Ready” (LOL)!
Retain the broadband design of the amplified loop on a sturdy form
Shrink the size to fit into a backpack without heavy stand or long pole
Build a modular platform that would allow quick setup
Be something durable that can last me 20+ years of use
Allow the loop to be rotated and tilted by hand
Be easy to hook up to any kind of radio
and later on, Enhance the design as a true Ferrite Sleeve Loop
The Backpack: The existing photo backpack was slightly too bulky. Found on Amazon was an Adidas Excel II XXL backpack on special sale with plenty of tall compartments and minimal padding. It is surprisingly roomy and comfortable to wear with springy shoulder straps and padded mesh backside!
Sturdy Basic Form: The Backpack Shack loop was originally built on 14-inch quilters loops (three of them) in a parallel configuration. I thought to simplify the whole thing and just use one wide loop. But what should I use for a sturdy form? The quilters loops were too flimsy and PVC pipe was too heavy. I stumbled upon a nice company called FlexPVC which allows sales to the public of various kinds of PVC pipe. Their Thinwalled Air Duct PVC looked promising. It is thinner than regular PVC but having standard inside dimensions and comes in custom-cut lengths. I decided 10-inch diameter would fit best inside the Backpack. FlexPVC even sends you a small booklet of the U.S. Constitution and the Bill of Rights with your order! 🙂
Thinwalled PVC form
The “length” as they call it would be my form width for the copper strip. I thought 3-inch would be nice but decided 4-inch was better. Supposedly, the aperture + the width of the “radiant element” is the main design consideration for loop performance. So, I figured that as wide an element as I could get away with was better.
Stable Mounting: Now, how to mount this thing! I eventually went back to my photographic web links and found nice rig equipment for video cameras. The typical construct is made of 15mm tubes of aluminum or carbon fiber (CF) and fit into adapters that allow attachment to other adapters or clamps. Non-metallic CF seemed ideal, so, I ordered a whole bunch of items from eBay to experiment piecing together two 10-inch CF tubes mounted inside the PVC form. Then, I attached two 15-inch CF tubes to the bottom of the PVC with something called a “Cheese Rod” that has multiple holes. Those two tubes are attached to another “Cheese Bar” which is attached to a second Cheese Bar on a cheap two-axis tripod head. This is a simpler photo version with quick release plate that locks pan-tilt separately and only cost $16.
Cheese Rod attached to bottom of PVC
Pan-tilt head assembly with Quick Release plate
For the base, I had an unused Sirui T-2005X 5-Section Aluminum Travel Tripod going to waste, so it was pressed into service. Very good tripod: can hold 26 lbs. (forged aluminum, not cast aluminum), legs can flare out for stability, and folds to 14.5-inches. Now, everything could come apart and fit into the Excel II Backpack!
Critically, the video rig standardization in the DSLR industry allows me to pick and choose parts from any cheap manufacturer but end up with a system that looks and feels coherent, is both sturdy and light, and can come apart if needed. Also, the pan-tilt photo head is really easy to work to get maximum peak or null out of the loop when mounted to a camera tripod.
CF Problem: CF tubes have no internal threads like that of aluminum tubes. So, I attached two, small 3/8-1/4 inch tripod adapters to the ends of a 3/8-inch oak dowel inside each CF tube destined for the inside of the PVC (ridiculously, I used up almost a whole bottle of super glue to get these 4 tiny pieces to attach to the oak dowels). This is definitely a weakness of my design but I could not figure out any other way to get the CF to mount inside the PVC form. Then, added to this is something wonderful I found at Ace Hardware called “speed nuts” to help push ipwards against the incoming stainless steel socket head screws of exact length. With jam nuts, internal lock washers, wing nuts, and strategic use of Thread Locker Blue, I finally had enough confidence that this thing would hold together!!
Speed Nuts pushing upward against incoming screws
Super-glued 3/8-1/4 inch adapter on end of oak dowel inside CF tube
Bottom assembly (Cheese Rod, Cheese Bar, and 15mm Clamp screwed together + wires to a BNC connector)
Ferrite Sleeve Loop: Halfway through this project, I became determined to use the ferrite bars and rods I had purchased from eBay mid-summer 2017 to turn this antenna into a real Ferrite Sleeve Loop but with a broadband design (At that time, I ended up purchasing the very last quantities of 62x12x4mm ferrite bars from the Lithuanian eBay seller, just because they were becoming scarce plus some other 8mm ferrite rods). The Thinwalled PVC is 5mm thick, perfect for this type of application. The video equipment could handle the extra weight. I had just enough ferrites to line the inside of this PVC form with two bars side-by-side all the way around the inside (plus some shorter ferrite rods at the top and bottom). Some quick setting JB WELD Kwik Weld epoxy made quick (and permanent) attachment of these ferrites to the inside of the PVC. Now, the bars stick out from the PVC form by about ½-inch on each side, so I do have to be careful it does not get abused and chip off any of the exposed ferrite.
Soviet ferrite bars and rods, 400 ui (initial permeability).
Note: Using Gary DeBock’s Performance estimate (diameter * length), this calculation predicts that this FSL 10.75-inch loop should perform similarly to Gary’s 10-inch models using 140mm long Russian ferrite bars (mine probably performs less than his since I am not using carefully tuned (to Mediumwave) litz wire on higher permeability 1500 ui ferrites like he does).
Preamplifier: I believe one advantage of building a portable, table-top loop antenna like this is that all the connections are short. This allows me to use a Preamp right at the connection point of the loop. Indeed, this was critical since passive testing (no Preamp, nor ferrites) found that this loop is somewhat deaf at the MW frequencies and uninspiring on the SW bands. This was true even when connected to Antenna A of my SDRPlay RSP-2 and the internal Low Noise Amp cranked all the way up. So, I ordered the DX Engineering RPA-2 Preamp. This adds to the weight somewhat since I also needed a 12V battery supply using a 10-cell holder of NiMH AA batteries and 2.1mm plug.
The question arises that I “should” impedence-match the output of the loop before anything else to increase “maximum gain”. Well, for one thing, a tuner or matching balun would just introduce loss as soon as the wire comes out at the base of the antenna. The slight net increase in gain does not seem worth it; the signal/noise ratio rarely changes when introducing a device that is meant specifically for matching a transmitter to a load. Receiver circuits don’t care as long as there is enough signal to process. That is what the Preamp is for. The Preselector is for rejecting out-of-band (i.e., increasing signal/noise ratio + eliminate overloading the electronics).
Preselector: Now that the signal level was satisfactory, I added on the Cross Country Preselector, which I like very much since it is passive, lightweight, and well made. I had looked at other amplified preselectors but found the schematics showing the preselector came first in the path. I needed the preamp first, so that is how I ended up with separate units. In fact, the reverse configuration performs with worse signal/noise ratio because of the loss inherent in the preselector. In this case, it is definitely needed to amp the loop first with a high quality preamp (high IP3 rating)!
Automatic Bypass: The Cross Country unit has a great feature in the “off” position as an automatic bypass. This feature is very important since I do not need a Preselector in the circuit all the time. The bypass feature also allows the RSP-2 to monitor a large swath of spectrum without having the Preselector cut the bandwidth. The DX Engineering RPA-2 Preamp also has a circuit bypass when the power is off – very nice feature! So, I can keep all the antenna wires connected if I don’t want to use either device on a certain band – necessary for my broadband antenna design and use with an SDR.
Modular Portability: Another advantage of a table top loop is portability. Because of the modular design, I can put this into checked baggage (except for the AA batteries and laptop) and have it available for DXing in unexpected places. It could be useful when traveling and I cannot string wire into a tree but want something better than a whip antenna on a small radio. Everything fits into the bag and can be setup on a balcony, inside a car with a sunroof, or on a park picnic table.
A third advantage is that a short antenna could be clamped to one of the tubes and then connected directly to Antenna B of the RSP-2 for listening to higher frequencies (like a Comet W100RX). This expands the usefulness of this project as a platform for multiple antennas!
Finished Loop and accessories assembled together
Performance: Good on MW and very good on Shortwave. It is not in the league of Wellbrook antennas but it is useful as long as the RSP-2 LNA is kept down around -7 on MW and -4 on SW, else it overloads. The photo gear makes it easier to use than the original loop. I found that one side has a slightly larger receiving lobe than the other which is OK in practice. The null is very sharp and takes a little finesse to null out an offending station by almost 20 dB on MW and 15 dB on SW (the photo head can lock in place). It is handy to have the pan-tilt arm point directly at a station to maximize the null since the arm is mounted perpendicular to the loop. I will look for a clear plastic bag to cover the antenna and electronics to use in wet environments.
A larger loop would work better but this one is to use wherever I can. Also, my work laptop is noisey and shows birdies and spikes here and there on the bands, so I added a large ferrite bead to the USB computer end which helps. But I don’t have to use an SDR, I just have to change a connector and radio. It was expensive and fun to build – I guess I am just LOOPY!
Appendix I, Field Recordings 27-Jan. 2018 between 21.26-22.36 UTC:
Note 1: All Transmitter locations referenced from web site short-wave.info at time of recordings
Note 2: My location in a shelter at Dick Young Forest Preserve (41.84334, -88.38133)
Note 3: Moderate but declining solar wind with no flares, Kp Index = Calm (1)
10 AA Powerex Precharged NiMH batteries for the Preamp + 10x AA snap battery holder + CCTV 2.1mm snap plug
1 Cross Country Preselector
1 SDRPlay RSP-2 with SDR Console software on Lenovo laptop
1 Belkin USB printer cable with large ferrite bead looped through 3 times on computer end
1 Sirui T2005X travel tripod
1 Adidas Excel II XXL backpack (gaudy Solar Orange color!)
Velcro brand 7/8” x 23” One-Wrap velcro strips
Plus shielded cables, BNC and SMA adapters, Thread Lock Blue, tie wraps, rubber bands, super glue, JB WELD Kwik Weld epoxy, speed nuts, jam nuts, acorn nuts, wing nuts, internal lock washers, nylon nuts and screws, and 1/4”-20 socket head screws of various lengths as needed.
What a brilliant project, Tom! What I love is the fact that you consider your unique requirements prior to starting a project and base your design on your specific needs. Additionally, you see each design as an iteration. Fantastic job! No doubt, you’ll log numerous hours with this antenna in the field! Thank you for sharing your detailed design notes, process, list of materials and even audio clips with us.
Many thanks to SWLing Post contributor, TomL, for sharing the following guest post:
August 21, 2017: Individual Recordings of MW During Totality
I setup flimsy “Backpack Shack” loop antenna and preselector to my Sony ICF-2010 to listen to any propagation of MW signals as each transmitter experienced Totality. My location was a picnic area facing southwest with only a small hill to the east at Ferne Clyffe State Park near Goreville, IL.
I did not bring a DSP radio and computer which would have been better in hindsight. My observations were generally as follows:
Anything west of my location, except for local St. Louis stations were not identifiable.
Noise levels were somewhat elevated because of thunderstorms that had just moved through the area during the evening.
Anything east of my location experienced dramatic increases in signal along the path of totality.
Since large signal increases were seen with the Umbra moving AWAY from me, it would be more beneficial to use a DSP receiver with good outdoor antenna than a single frequency radio and preselector like my setup. The loop antenna sitting on a picnic table acted great and was usable to get strongest signal for each station.
It is still unknown why I could not identify any stations west of me with the Umbra moving TOWARDS my location and needs further study. I thought I heard KTWO in Casper WY, but upon listening to the recording, it was a male announcer buried in the noise and unintelligible.
A transmitter being IN the path of Totality has a better chance of lasting longer with a strong signal than one that is just outside of Totality. Compare behavior of WSB vs. WBT.
If this happens again, make sure to make multiple hotel reservations and cancel the ones not needed. Traffic was horrible and had to stay in a hotel half way from home and I aggravated an achillies heel problem in the stop and go traffic (YUK).
So, it was quite disappointing to not hear anything special west of my location. As Totality neared my site, I just left the radio tuned to KNOX for the people around me to hear. Its signal did become about 25% stronger and near the end of the recording you can hear other weaker stations trying to break in.
As soon as totality was over, and my picture taking was done, I returned to the radio and found 1510 khz WLAC Nashville, TN was moderately strong! And this was seconds after their Totality had already ended. A baseline reading beforehand showed this station coming in very very faintly. Subjective SINPO rating beforehand=15452, just after Totality=34433.
The next surprise was tuning to 750 WSB Atlanta GA was BOOMING in! They were very clever and had no announcers. Instead they were playing snippets of songs about sun, moon, dark themes. Very entertaining! Baseline beforehand was just moderate noise, no signals. During recording, SINPO=55444 with propagation getting slightly worse near the end of the recording.
Final surprise was 1110 WBT Charlotte, NC, which was not in the path of Totality but just north of it also booming in but not as strongly. Also, near the end of the recording, the signal dropped off very sharply, unlike the WSB signal which stayed strong throughout the 5+ minute recording. Baseline beforehand was low noise and no signals. During recording, SINPO=43434 at 14:40 ET, then approximately 1½ minutes after their maximum eclipse (14:43 ET), SINPO=33423, then at 14:46 ET a SINPO=22422 with another unidentified station breaking through playing a Johnny Cash song.
Tom, thank you for taking the time to share your recordings and listening experiences with us! Snagging a daytime MW broadcast from the Atlanta, GA and Charlotte, NC regions is most impressive. I reckon they were about 400-500 miles (as the crow flies) from your Ferne Clyffe, IL location.
Sounds like you had an amazing experience, despite the stop-and-go traffic!
Many thanks to SWLing Post contributor, TomL, for the following guest post:
“Car Shack” radio listening
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
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,
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.
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)
I have made the following changes:
Created a prototype mini-loop based on a crossed-parallel idea from VE1ZAC (Jeff).
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.
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!
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