Category Archives: Antennas

Gary DeBock experiments with FSL antenna nulling to eliminate a “pest” station

Many thanks to SWLing Post contributor and Ultralight DX enthusiast, Gary DeBock, for sharing the following guest post:

Nulling a local pest with dual FSL Loops

by Gary DeBock

After many dual FSL antenna experiments I’ve finally determined how to effectively cancel out QRM from a local pest that is off to the side (ideally 90 degrees different, but practical from 50 degrees to 90 degrees different) from a weak DX station, although I’m not quite sure of the theory behind this discovery.

This experiment was an attempt to cancel out QRM from a local pest, 950-KJR in Seattle, WA (35 miles/ 56 km to the north) and chase 950-KKSE in Parker, CO (1005 miles/ 1617 km to the southeast) during the early morning hours. The receiver was a basic (non-SSB) C.Crane Skywave, and two identical 5 inch ferrite rod FSL antennas were used. Please refer to the photo (above) to follow this description.

Step 1) Null out the pest station with the portable radio’s loopstick (away from the FSL antennas). Set the radio down in this nulled position, so that the pest station is as weak as possible, while ensuring that there is space to set up the FSL antennas to the back and side (see photo).

Step 2) Take the “Reception FSL” and use it to peak the pest station’s frequency, setting it up parallel to the portable radio as shown, at the position providing the maximum inductive coupling gain. This will temporarily boost up the pest station, which previously was nulled.

Step 3) Take the “Nulling FSL” and pretune the frequency to that of the pest station. You can do this either by adjusting the variable cap plates to match those of the “Reception FSL,” or by temporarily peaking the pest station’s signal in a position in front of the portable radio. After setting this frequency, set the “Nulling FSL” off to the side of the portable radio as shown, with the spacing identical to the spacing between the radio and the “Reception FSL.”

Step 4) Slowly and carefully tune the “Nulling FSL” until you hear the pest station’s signal take a sharp drop. This setting will be very sharp, but once you find this position you will have nulled out the pest very effectively, and if another station is on the frequency, it may suddenly become dominant, even if it is far away (like 950-KKSE in Denver).

Some MP3’s from this morning’s experiments:

950-KJR in nulled position with the portable only

950-KKSE generally dominant over the local pest KJR when the “Nulling FSL” is peaked

Fascinating, Gary! I don’t understand the dynamics of why this works, but it’s amazing that it does so effectively. I can think of two MW frequencies in particular where I could put a system like this to the test.

Thank you for sharing!

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Majority of YouLoops listed on eBay are not an Airspy product

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Many thanks to SWLing Post contributor, Chris Smolinski, who shared the screen shot above of a “YouLoop” being sold by a vendor on eBay.

While the Airspy YouLoop is based on a public domain noise-cancelling passive loop design that dates back decades (a.k.a. the Moebius loop antenna) buyers should note that many of the “YouLoop” antennas on eBay are not manufactured by Airspy. The product titles are misleading in this regard:

The RTL-SDR Blog does sell the original Airspy YouLoops on eBay for $34.95 shipped (and, as you can see above, they seem to pop up first in the search results).

Many of the other loops being marketed as “YouLoops” on eBay cost around $23.00-25.00 shipped. About $10 less, but there’s no guarantee the toroid windings, for example, will have the same specs as the original YouLoop.

It’s easy to spot the YouLoop copies because the cross over and toroid enclosures are much larger than those of the authentic AirSpy YouLoop:

Compared with the Airspy YouLoop:

Airspy doesn’t own a patent for the YouLoop (indeed, they even suggest homebrewing one) so this isn’t a clone. Rather, buyers should simply be aware that, as far as I know, the only authentic new YouLoops are being sold on eBay by the RTL-SDR blog.

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CHA MPAS Lite: Chameleon designs a new compact portable antenna system

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Many thanks to SWLing Post contributor, Don, who notes that Chameleon Antenna has just introduced the CHA MPAS Lite: a modular portable antennas system covering from 6M – 160 meters.

I know a number of participants in the Parks On The Air program who use the CHA MPAS antenna system–the MPAS Lite is the “little brother” of that antenna, according to Chameleon.

Although designed with the new Icom IC-705 and other QRP transceivers in mind, the CHA MPAS Lite can handle up to 100 watts in SSB or 50 watts in CW.

They plan to start shipping the antenna in early November 2020 and the price for the system is $340.00. That may sound like a lot of money for an antenna (it is, let’s face it!) but if you speak with pretty much anyone who owns a Chameleon antenna they’ll tell you it’s worth it. The quality is second to none. I’ve been testing their Emcomm III wire antenna recently and it must be one of the most robust portable wire antenna systems I’ve ever evaluated.

Also, all of their products are designed and manufactured in the USA.

Click here to check out the CHA MPAS Lite product page.

We recently added Chameleon Antenna to our list of sponsors here on the SWLing Post. I’m very proud to include them because one of my personal missions is to promote mom-and-pop companies that push innovation here in our radio world! It’s humbling that they support us too.

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Taking the Par EndFedz EFT-MTR triband antenna to the field!

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The Par EndFedz EFT-MTR triband (40/30/20M) antenna

In July, I purchased a tiny QRP transceiver I’ve always wanted: the LnR Precision MTR-3B. It’s a genius, purpose-built little radio and a lot of fun to operate in the field.

It’s also rather bare-bones, only including a specific feature set built around ultra-portable CW operation.

While the MTR-3B has features like CW memory keying, a wide operating voltage (6-12 VDC), extremely low operating current (20 ma in receive), real-time 24 hour clock, and a full compliment of keying adjustments, it lacks other features like a volume control, SWR meter, speaker, and built-in antenna tuner.

Some of those may seem like big omissions but SOTA and POTA activators who like extremely lightweight/portable gear love the MTR-3B for being so purpose-built.

The MTR-3B (and its predecessors) operate on three bands: 40, 30, and 20 meters. These are, without a doubt, my favorite bands when operating portable since antenna lengths are reasonable.

Since the MTR-3B doesn’t have an internal ATU, you need to pack an external tuner or, better yet, a resonant antenna–ideally, one that can be used on all three bands.

Although many of my portable transceivers have built-in ATUs, I rarely use them because I primarily operate with resonant antennas. Resonant antennas are more efficient–giving you the maximum mileage per watt. In addition, they’re also more simple: connect them to the rig and hop on the air. No tuner or tuning required.

Since I keep self-contained field radio kits, my MTR-3B needed a dedicated resonant antenna.

The EFT Trail-Friendly antenna is incredibly compact and quite easy to deploy.

I’ve mentioned in previous posts that I’m a big fan of the Par EndFedz Trail-friendly EFT tri-band antenna (above) which is resonant on 40, 20, and 10 meters. I’ve activated well over 130 parks with this little antenna.

After I took delivery of the MTR-3B, I borrowed the Trail-friendly EFT antenna from my KX2 field kit. It worked well on 40 and 20 meters, but it doesn’t cover the 30 meter band. Also, by borrowing the EFT from the KX2 kit, I broke one of my rules: never borrow from one field kit to feed another. This led to me leaving the EFT hanging in a tree at a remote park and returning a week later–a three hour round-trip(!!!)–to retrieve it. (FYI, in all fairness, I also blamed my trusty canine companion for this mishap!)

Enter the Par EndFedz EFT-MTR triband antenna

A few months ago, Vibroplex purchased the Par antenna line from LnR Precision.

I was very pleased with this decision as I’m guessing LnR Precision wanted to hand off antenna production so they could focus on the very popular Mountain Topper transceiver line.

Vibroplex is owned by my buddy, Scott Robbins (W4PA), who is not only a successful entrepreneur, but also an award-winning contester and DXer. I’ve known Scott for years and knew he’d not only be a great steward of the Par product line, but also push new innovations.

I emailed Scott asking if Vibroplex had a field-portable antenna that would be resonant on 40, 30, and 20 meters. Turns out, there’s a Par antenna designed specifically to pair with the MTR-3 series transceivers: the Par EndFedz EFT-MTR.

Scott pointed me to a description of the antenna on the Vibroplex website:

The new EndFedz ® EFT-MTR is a 40m/30m/20m tri-band QRP antenna rated up to 25 watts. The “MTR” name was selected as LNR Precision developed this antenna to be the perfect companion to the wildly popular 40/30/20m Mountain Topper QRP transceiver. The EFT-MTR’s total length is 65′ of 22 AWG polystealth wire and weighs less than 4 ounces! It is built with the same high level of workmanship and quality that you have come to expect with all EndFedz ® antennas.

A particular innovation on this antenna: This EndFedz is a little different than previous designs. The user has the option to remove an SMA connector at the end of the 30M resonator to enable just 30 meters, or keep the SMA installed for 40 and 20 meters. Because of the broad bandwidth of the antenna, it is unlikely that it will require tuning in the vast majority of deployments. This is particularly true of 30 meters where the band is very narrow. As our tagline states, “They Just Work!”

Included with the EFT-MTR is the EndFedz Antenna Winder. Conveniently allowing winding up the antenna line to not have a tangled mess at the end. The winder will hold both the antenna and 25 feet of RG-174U coaxial cable (optional accessory).

Scott offered to send me an EFT-MTR to evaluate in the field (disclaimer: at no cost to me) and I accepted without hesitation, of course!

An EFT-MTR field review

I’ve taken the EFT-MTR antenna to three park activations at this point and have formed some opinions about it.

The EFT-MTR fits perfectly in a slide-in pocket in the main compartment of the Boot Boss.

First of all, I couldn’t be more pleased with the size as it fits perfectly in my MTR-3B field kit built around my Red Oxx Booty Boss pack.

I really like the built-in antenna winder: it’s larger than that of the EFT Trail-Friendly, but also much easier to wind up and manage post-activation.

I’ll admit, the length of the EFT-MTR was a bit surprising the first time I deployed it: 65 feet. Keep in mind, though, I had been used to a much shorter 41 foot radiator on the EFT Trail-friendly. Occasionally, I operate in spots where I simply don’t have the room to deploy a long antenna. I also worried that the EFT-MTR resonance might be negatively affected by winding its way through trees and over a branches. The MTR-3B transceiver does not like high SWR values and has no built-in SWR meter to monitor it. Last thing I wanted to do was harm the MTR finals.

You might be able to spot the feed point of the EFT-MTR at my activation of K-6952 this week.

Fortunately, winding its way through trees doesn’t seem to have a significant impact on SWR.

Each time I’ve taken the EFT-MTR to the field, I’ve also taken my KX2 which I’ve used to read the antenna’s SWR value. So far, the difference has only been negligible and SWR well within the tolerances of the MTR-3B. Score!

I should note here that since I’ve started using an arborist throw line, I’m also able to hang antennas much higher than I could before. This has had a huge impact on all of my field activities.

Removing the SMA cap changes the EFT-MTR from a 40/20 to a 30 meter resonant antenna.

To be resonant on 40, 20 and 30 meters, the EFT-MTR requires a field modification. On the coil about 2/3 the way up the antenna, there’s an SMA connector with a small screw on cap (see above). When the cap is on (thus completing the connection) the antenna is resonant on 40 and 20 meters. You must remove the cap for it to be resonant on 30 meters.

Since I’ve been using the EFT-MTR, I start an activation on 40 meters (which is typically my most productive band), then move to 20 meters (typically, my least productive). If I have the time, or need the extra contacts to confirm a valid activation, I lower the antenna, unscrew the SMA cap, and raise the antenna again.

I thought at first this would be a major pain, but it hasn’t. Now that I’m using an arborist throw line, it’s super easy to lower and raise antennas. But even when I’ve used fishing line, it really hasn’t been an issue.

The only issue I see is I’m afraid I’m going to lose that little SMA cap in the field. To prevent this, I’ve made it a routine to immediately put it in the internal zippered compartment of the Booty Boss pack. I might find a source for those caps, though, just in case I still lose this one.

I’ve been very pleased with the EFT-MTR’s performance. I’m guessing it’s actually higher gain than my beloved EFT Trail-Friendly antenna. On my last activation with the EFT-MTR, I knocked out eight 40 meter contacts in about eight minutes during a period of poor propagation. Note that the MTR-3B was only pushing 3 or 4 watts of power.

I then moved to 20 meters where, frankly, propagation was so crappy I didn’t hang out there long. Instead, I lowered the antenna, removed the SMA cap, and started calling on 30 meters. Within a few minutes, I racked up the rest of my contacts.

I was very pleased with how quickly the Reverse Beacon Network picked up my CQs and was thus auto-spotted on the POTA website.

Conclusion?

If you own a Mountain Topper MTR-3 series transceiver, I highly recommend the EFT-MTR antenna. As with my EFT Trail-friendly and Par sloper, the quality is top-shelf. I expect the EFT-MTR will last even longer than the EFT Trail-friendly since the winder is so accommodating and the in-line coil is designed so that it doesn’t snag on branches as easily.

I’m looking forward to much more field fun with the MTR-3B and EFT-MTR combo!

Click here to check out the EFT-MTR at Vibroplex.

Click here to check out Vibroplex’s full line of antennas.

Many thanks again to Scott at Vibroplex for sending me the EFT-MTR for evaluation!

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Bruce compares two homebrew NCPL antennas to the Airspy Youloop

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The Airspy Youloop

Many thanks to SWLing Post contributor, Bruce (VE3EAR), who writes:

I decided that more testing of the Noise-Cancelling Passive Loop (YouLoop) antenna was needed, but I wanted to start with a clean page.

I built two identical loops using some 3/8 inch heliax scraps I had on hand. Both are one metre in diameter and employ the same feed arrangement, with a balun wound on a half inch square binocular core of type 75 mix. There are four turns on the antenna side and eight on the feed line side, of #24 gauge plastic insulated wire. The feed line shield connects to the antenna shields. The only difference between the two antennas is at the top of the loop, opposite to the feed point. One has a simple one inch gap in the shield, with the centre conductor passing across the gap, while the second one uses the crossover connection of the YouLoop design.

I’ve been running some A-B comparison listening sessions, both mid-day and in the evenings after local sunset. The testing is done outside, with the antennas hanging on a low limb of a maple tree in front of the house. The feed line is about twenty feet of coax which connects to my Realistic DX-440 receiver on the front porch. Testing is done listening to the AM broadcast band and the 160, 80, and 40 metre ham bands, with the loop aligned both E-W and N-S and about one loop diameter off the ground.

Both loops work well, but I do have to give the nod to the YouLoop (by Airspy), which produces a stronger signal of two S-units higher than the conventional loop. It also has deeper and sharper nulls, which can sometimes produce total nulling of the station!

73, Bruce, VE3EAR

Thank you so much, Bruce, for sharing your findings with us! I, too, have found that the Youloop generally outperforms my homebrew NCPL antenna. I believe one of the reasons for this as Youssef at Airspy once told me is because the Youloop has a lower loss transformer than anything that can be wound by humans (0.28 dB)–this improves gain.

Click here to read our review of the Youloop and click here for step-by-step instructions on building your own Noise-Cancelling Passive Loop antenna.

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Giuseppe’s cross-loop experiments

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Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who shares the following:

I’m Giuseppe Morlè from Formia, central Italy, on the Tyrrhenian Sea.

I wanted to share with you and friends of the SWLing Post community this antenna project of mine dedicated to those who do not have enough space on the roof or in the garden to install antennas.

These are two separate loops, with two different diameters, one 60 cm, the other 90 cm, each with two variables for tuning … the system is able to receive from 3 to 30 MHz.

I joined these two loops in an opposing way, better to say crossed that can communicate with each other due to the induction effect that is created between the two small coupling loops that are placed one under the other at the top.

In the videos you will be able to see how the antenna system receives. I can use one loop at a time, to detect the direction of the signal or I can use them together for a more robust signal and in an omnidirectional way.

I really like experimenting with the induction effect and you can see that even when closed at home the two loops do a great job.

From my YouTube channel:

I’m not a technician but I really want to experiment to try to listen as well as possible.

Thanks to you and CIAO to all the listeners of the SWLing Post community.

Giuseppe Morlè iz0gzw.

Very cool, Giuseppe! I must say I’ve never tried dual loop experiments like this where one can experiment with the induction interplay. I imagine this could give you some interesting nulling capabilities if you have an unwanted station interfering with a target low-band signal. Thank you again for sharing!

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Jorge’s Portable YouLoop Antenna Frame

BricoDX: A YouLoop portable frame

by Jorge Garzón (EB7EFA · EA1036 SWL)

Youloop ‘in the forest’

One of the aerials I wanted to test was the Youssef Loop (YouLoop). I own a good passive loop antenna made by Tecsun (AN-200) but this is a mini one to use with portable receivers. A video showing the test of this ‘mini-loop’ can be seen in my YouTube channel.

My main loop for serious DXing is the Wellbrook 1530LN, but this is an active loop that easily beats any other passive ones. It’s close to be the perfect loop for me as I live in a rural valley with low noise level in the bands so I enjoy every minute of my listening sessions. However I wanted to test this newcomer passive loop, but wasn’t satisfied just hanging it from a pine tree branch, so I decided to bring about my DIY YouLoop portable frame project.

So I had to find something to get a rigid (but light) support for the loop itself allowing an easy rotation to achieve deep nulls. So… what could I built?

Fiberglass tubes, hooks and crossed arms.

I am professionally involved in the heritage and communication sector, so was easy for me to refit some dismissed display rolls where I found a 1,5 m thin supporting tube made in fiberglass that suited my needs. I cut a piece of 120 cm and then split it into 2x60cm, tightening both in the middle with a fine bolt. I placed two plastic hooks up and down of the vertical tube to hold both Youloop modules. The horizontal arm was lengthened with two bamboo meat skewers firmly inserted into the tube, allowing to slide onto it. Two small holes in the bamboo pieces were good enough to secure the cable with a short wire. All this was well fixed with clamps and vulcanized tape to an extra piece of vertical tube.

Bamboo meat skewer and tied cable.

Finally all this was inserted into a thicker aluminium tube and then into a wider one in order to fit everything into the tripod hole and then get a smooth and efficient rotation of the antenna. As a base I re-fitted an old heavy metallic tripod manufactured by Manfrotto (Italy) that I used it often for birdwatching day trips. I gave back an unexpected new life for this piece of metal, always in the field close to Nature!

The whole assembly can be easily transported in the car. Aluminium tubes slide one into the other, being rapidly detachable from the loop itself. This is a cheap and DIY project to get the maximum of this surprising and low noise passive loop.

This aerial gives its best performance when used in the field. There, QRM levels are low or non existent at all. It is a must to rotate it easily and then get sharp nulls. SMA connector nuts must be well tightened as they tend to loosen easily, but beware to force them as an extra twisting could damage inner connections.

This is the first post of a series called «BricoDX» where I will show how to refit or build accessories to get inexpensive and practical DIY projects for our listening sessions.

Many thanks for sharing your article with us, Jorge! That’s a brilliant loop support.

Readers: check out more of Jorge’s articles on his blog, @IberiaDX. Also check out his YouTube channel where he posts videos.

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