Category Archives: Antennas

The NooElec Balun 1:9 v2

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Many thanks to SWLing Post contributor, Grayhat, who writes:

Hi Thomas, was about to write you about some infos related to the NooElec balun when found that they now offer a v2 model:

https://www.nooelec.com/store/balun-one-nine-v2-barebones.html

The new balun has the same schematic as the previous one:

But it is slightly bigger, has a better connector for the antenna wires and (according to NooElec) uses a transformer which allows the tiny balun to work more efficiently from 0 to around 70 MHz (check out the charts found in the downloads section of this link).

The transformer used, judging from the pics, is a CoilCraft WB9-1, whose data can be found here:

https://www.coilcraft.com/wb_th.cfm

As I wrote the reason for this was the fact that a friend of mine reported that he used the (v1) balun with a Loop On Ground (LoG) Antenna !

If you look at the schematic (above) you’ll notice that there’s a “jumper” labeled R1 (zero Ohm resistor). That tiny detail is important, see, leaving the balun as is, it will work fine with a longwire, one just connects contact #1 to the antenna and #2 to a counterpoise or ground system and there he goes, BUT there’s another way to use the balun, that is, CUT the “jumper” (ok, resistor) labeled “R1”. If you cut it, the balun will become a 9:1 isolation transformer and with such a modification will work just fine with the KK5JY “LoG”
antenna: http://www.kk5jy.net/LoG/

According to what my friend reported, the balun works just fine, and although probably the ferrite core used in the V1 isn’t up to par with the original one used by KK5JY, the difference isn’t so huge.

Oh, and I also suspect that the modified balun may work fine with the KK5JY simpler passive loop http://www.kk5jy.net/rx-loop/ which may be a nice antenna for restricted spaces!

I think it may be of interest to people not knowing/willing to wind their own baluns, at that point one may just need an enclosure to protect the balun and putting up a receive antenna will be as easy as 1-2-3.

Thank you for sharing this! Readers: Grayhat has been encouraging me to deploy a LoG antenna at my home and I do plan to do so in the coming months. Please comment if you use a LoG similar to the KK5JY model and what your results have been.

Thank you again for the tip, Grayhat!

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Rolf experiments with MW antenna coupling

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Many thanks to SWLing Post contributor, Rolf, who writes:

I made a great discovery tuning using a second passive analog radio.

When I tune to Radio Caroline, for example, on my portable I can receive the signal okay. When I put the receiving radio on minimum then place it next to and couple it with the second radio, it is receiving a lot better!

Even stations I could hardly hear, now i can hear them!

Check out my short demonstration video:

Click here to view on YouTube.

That is fascinating, Rolf. Thank you for sharing. Indeed, this is one of the reasons why I try to maintain a good distance between radios when comparing them in reviews. In this case, though, you’re using coupling to your advantage!

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Mediumwave DXing: Radio setup offers “cheap thrills”

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Many thanks to SWLing Post contributor, Rich Stahl (WR3V), who shares his frugal but effective mediumwave DXing setup:

My MWBC directional reception on the cheap (see photo above):

Tecsun PL-310ET $40.85
Tecsun AN200 loop $12.95
Walmart Lazy susan $7.95
Cardboard box -0-

Total $61.75

Who says its an expensive hobby?

Indeed! That’s a very basic, yet very effective setup, Bill. Thanks for reminding us that this doesn’t have to be an expensive venture!

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A liquid-based VHF/UHF steerable antenna

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Many thanks to SWLing Post contributor, Marty, who shares this fascinating article from the IEEE Spectrum:

A new antenna that uses saltwater and plastic instead of metal to shape radio signals could make it easier to build networks that use VHF and UHF signals.

Being able to focus the energy of a radio signal towards a given receiver means you can increase the range and efficiency of transmissions. If you know the location of the receiver, and are sure that it’s going to stay put, you can simply use an antenna that is shaped to emit energy mostly in one direction and point it. But if the receiver’s location is uncertain, or if it’s moving, or if you’d like to switch to a different receiver, then things get tricky. In this case, engineers often fall back on a technique called beam-steering or beamforming, and doing it at at a large scale is one of the key underlying mechanisms behind the rollout of 5G networks.

Beam-steering lets you adjust the focus of antenna without having to move it around to point in different directions. It involves adjusting the relative phases of a set of radio waves at the antenna: these waves interfere constructively and destructively, cancelling out in unwanted directions and reinforcing the signal in the direction you want to send it. Different beam patterns, or states, are also possible—for example, you might want a broader beam if you are sending the same signal to multiple receivers in a given direction, or a tighter beam if you are talking to just one.[…]

Click here to read the full article.

 

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“G8JNJ Reverse Engineers and Reviews the MLA-30”

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Many thanks to SWLing Post contributor, Paul, who shares the following story from the RTL-SDR.com blog:

Last month we posted a collection of reviews about the MLA-30 which is a budget magnetic loop antenna designed for receiving HF signals. The overall consensus from the reviews was that it worked decently for the price, but of course could never live up to the high end loops that cost hundreds of dollars.

Recently Martin (G8JNJ) reverse engineered the active circuit used on the loop from photos taken by M0LMK and has made some observations on it’s performance, noting that it’s design isn’t very good. First he notes that the amplifier chip is a Texas TL592B two stage video amplifier which isn’t that great for this application. His measurements show an OIP3 of 20dBm, a P1 saturation of -3dBm and a noise figure of 12dB.

Of interest, he explains that the creator of this loop has designed it poorly as the impedance match of the loop to low pass filter is very wrong, resulting in a very poor amplitude/frequency response. He shows how the response can be improved with a few termination resistors, but is still not great.[…]

Click here to read the full article at RTL-SDR.com.

 

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Radio World: Construct an EAS Receive Loop Antenna

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The completed antenna, showing the F-connector on the tee box. (Source: Radio World)

Many thanks to SWLing Post contributor, Kris Partridge, who shares the following antenna construction article from Radio World:

Ken Beckwith is a field engineer with EMF based in Nebraska. Being a hands-on engineer, Ken has done his share of construction over the years. One of his projects was the construction of an octagonal-shaped AM loop EAS antenna using PVC pipe.

[…]The antenna has a broad coverage angle with a deep null when the antenna is broadside to the signal. Aim the “edge” of the loop toward the AM station you want to receive. The strongest signal will be received when the antenna end or edge is pointing to the signal source. The antenna can be mounted on a mast with U-bolts, hose clamps or whatever else works.

Here’s the construction parts list:

A 10-foot length of 3/4-inch diameter, schedule 40 PVC conduit cut into the following lengths:

2 – 4-inch
1 – 2-inch
1 – 2-1/4-inch
2 – 2-1/8-inch
6 – 9-1/2-inch
1 – 23-1/4-inch

Whatever is left over can be discarded, but before making your cuts, cut the flared end off, so all cuts are even.

1 –  3/4-inch 90 degree elbow
2 – 3/4-inch tee
8 – 3/4-inch 45 degree elbows
1 – 3/4-inch cap
1 – 3/4-inch tee box, plastic, with weatherproof gasket
1 – 7-foot piece of Belden 8777 or other three-pair shielded cable
3 – 7-foot single-pair shielded cables can substitute for Belden 8777
PVC primer and cement
Wire nuts or other connectors
1 – 3/8-inch ring terminal
F connector barrel with nut

[…]

Click here to read the article which contains step-by-step instructions.

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Marty needs advice as he builds a passive magnetic loop antenna

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Many thanks to SWLing Post contributor, Marty Kraft, who asked that I share the following question with our community:

I’m still working on a receive-only passive hula loop magnetic antenna for my Tecsun PL-660.

After viewing thousands of YouTube videos (LOL), I built the PVC-pipe structure [you can see in the photo below].

But I need some tech help to finish…

The antenna is 90 inches tall; large loop diameter is 40 inches; and small loop diameter is 17 inches. The wiring is 14 gauge braided.

I plan to put the antenna outside on the porch. Then I’ll run coax from the small loop to the receiver inside and use a 365 pF air variable capacitor to tune the large loop.

My first question is, what’s the best coax to use for the 10-ft run from the small loop to the radio inside? Second, will that 365 pF cap tune the entire 3-30 MHz range?

It’s hot here in Louisiana, so I’d really like to tune the capacitor from inside my apartment, also using coax to connect the cap to the large loop. Will that work? Or does the cap have to connect directly to the large loop?

Any other tips or suggestions? Thanks for the help!

Post Readers: If you have any helpful advice for Marty, please comment!

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