Tag Archives: Mag Loop Antennas

LZ1AQ Evaluates Impact of the Height Above the Ground on Mag Loop Performance

Source: LZ1AQ

Many thanks to SWLing Post contributor, Harald Kuhl (DL1AX), who shares the following article on LZ1AQ’s website:

Published on: 2018/11/20, Rev. 1.0 July 2018, Rev. 1.1 Nov 2018

Author: Chavdar Levkov LZ1AQ

Setup

Two identical small loops were placed one above the other according to Fig.1. One of the loops is very low – almost on the ground. The other one is placed at height which usually is used by the loop users. Two AAA-1C wideband active antenna amplifiers were used. Their gain difference was not more than 0.3 dB. The feeder was FTP cable each 20 m long. No cable baluns were used. The outputs were connected through two way antenna switch to a SD RX (Perseus). I used a measurement technique described in – A Periodic Switching Technique to Compare Receiving Antenna Performance in the Presence of Strong Fading. This is a precise method to compare two receiving antennas with real sky wave signals and the resolution can be less than a decibel. The idea is to switch periodically between two antennas and to estimate their difference on a calibrated graphic strength meter of a SD radio.[…]

Click here to read the full article.

I’ve often assumed height had little effect on the performance of an HF loop antenna–this evaluation seems to support that theory. Thanks for sharing this, Harald!

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MLA-30 loop antenna unboxing video

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Many thanks to SWLing Post contributor, Paul, who notes:

This video is in Chinese, but at least we can see what’s inside the box:

https://youtu.be/mM09pT1YbjU

Click here to view on YouTube.

Thanks for sharing, Paul.

If you’ve ordered the MLA-30, please let us know your thoughts about the construction and performance!

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Using amplified loop antennas with portable radios?

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SWLing Post contributor, Klaus Boecker, sports a homebrew magnetic loop antenna on his balcony in Germany.

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

I have a question about loop antennas; specifically which type is “better,” passive magnetic loops or active electric loops?

I know, “It depends.”–?

I live in a ground-floor apartment, with a small porch, lots of RFI and restrictions against visible antennas. Also there are no trees within 75 ft of my porch, which faces on a parking lot. My radio is a Tecsun PL-660, which works okay inside with my 10-ft bare wire antenna hidden on the porch.

With a loop antenna, I’d like to mount the antenna on the porch at night and have a remote tuner/control inside because it’s very hot n humid here in Louisiana even after dark.

No doubt there are a number of magnetic loop antennas that could serve you well in your situation, Marty.

To answer your first question, though, you should search for a wideband amplified loop antenna since you’re only concerned with receiving.

Passive loops are great antennas on the shortwave bands–and easy to build–but they best serve ham radio operators who wish to transmit. Passive loops typically have a very narrow bandwidth that requires the operator to constantly tune the antenna when they tune the radio a few kHz. Most amplified wideband loops need no separate tuning mechanism.

Last year, I posted an article about choosing the right loop antenna for situations like yours where one has limited installation options.

Click here to read : Shortwave antenna options for apartments, flats and condos

Portables and amplified loops?

I do hesitate to encourage you to invest in an amplified loop antenna when your only receiver is a Tecsun PL-660. Some portables don’t handle amplified antennas well–they can easily overload and I imagine you can even damage the front end of the receiver.

I’m well aware, however, that there are a number of readers here who do couple their portable radio to an amplified loop. I have connected a number of portables to large wire antennas and found they could easily handle the extra gain, so I imagine an amplified loop would perform as well; the Sony ICF-SW7600GR, Tecsun S-8800, and Sangean ATS-909X come to mind.

But the PL-660 is a hot little receiver even with the built-in telescopic antenna–I’m not sure if amplification would help or hinder.

Please share your experience

This is where I hope the amazing SWLing Post community can pitch in and help us out here!

Does anyone here regularly connect their PL-660 to an amplified loop antenna? If so, what model of antenna are you using? Are there other portables out there that you regularly connect to amplified loops? Please share your notes, thoughts and experience in the comments section.

Thank you in advance!

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Inexpensive wideband amplified mag loop receiving antenna on eBay

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Many thanks to SWLing Post contributor, Ola, who shares a link to this inexpensive mag loop antenna on eBay.

I have no clue if this antenna performs as well at all, but the price is certainly much lower than its competition at $47.99 US.

It appears you’ll need to supply your own dielectric center support for this loop–a length of PVC would do the trick.

Copycat–?

I don’t like the fact this manufacturer has chosen the name “Mega Loop Active” for their antenna as the name is too similar to Bonito’s “MegaLoop FX Active.” I don’t like the confusion that could create, so I would hope this Chinese manufacturer would change this in time.

To be very clear, this product has no affiliation with Bonito and I certainly would not expect the quality or performance you would get from a Bonito product. Bonito products are pricey, but they’re design and manufactured in Germany and set benchmarks in terms of performance and quality. I’m a big believer in “you pay for what you get.”

I suppose though if you’re just looking for a cheap antenna to test, this one is quite inexpensive. Just know that it is not a Bonito MegaLoop, despite the similarities in product name! 🙂

Click here to view on eBay.

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New indoor passive loop antenna for shortwave

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Many thanks to SWLing Post contributor, Dave Zantow (N9EWO), who notes:

Here is an interesting looking indoor passive HF loop antenna [photo above] that Randy McIntosh just started selling in the US. Made in Greece. Model TLA500C. Sorry it’s not for MW.

Here’ are the specifications/description from the eBay page:

This sale is for an HF magnetic loop antenna that should be attractive to anyone living in an apartment, residence, or other location where it is not possible to erect an outside dipole antenna. If you can erect an outside antenna, this is always the best solution for reception as no inside antenna can compete with a good outside antenna for the very best signal reception. But erecting an outside antenna is not always possible for many people desiring to listen to amateur radio or shortwave signals. Thus, this antenna offers a solution to such hobbyists handicapped by personal physical limitations to mount an outside antenna, minimal yard space to erect such an antenna, apartment living, or HOA restrictions.

This antenna spans a tuning range spanning 3.5 MHz through 40 MHz and thus covers 80 – 10 meters on the amateur radio bands, all international shortwave bands plus the 11 meter CB bands. The antenna comes with a 3′ coaxial cable to attach the antenna BNC output to a SO-259/PL-259 input of your receiver (most receivers).

Simple assembly directions are also included and you may be view this information in the last picture at the top of this listing. If you have a different input on your receiver other than the PL-259, you will need to acquire the proper interconnect cable from another Ebay seller. Assembly takes 5-10 minutes using only a proper sized Phillips head screwdriver and the antenna can be disassembled to transport to a remote DX location or for convenience in your travel luggage…..or as our picture shows, located permanently at your home listening room or bedside. Depending upon your preference and the dimensions of your receiver, the antenna can be set on top of or next to your receiver (see pictures at the top of this listing) during operation. Please remember that this is a “receive only” antenna and cannot be used to transmit signals.

Features:

non amplified….no batteries required

works on wide variety of communications receivers both stationary or portable

light weight aluminum construction weighs about 1 lb with the interconnect cable

portable – can be disassembled and folded into a low stature for compact transport

sharp tuning helps filter strong non-desired out-of-band signals

low noise loop design helps filter RF noise often found inside a home or apartment from lighting or appliances

tuning range of 3.5 MHz – 40 MHz

small loop antenna assembles to 18″ diameter at the broadest point

great alternative for signal reception when an outside antenna is not possible

very easy set up and connection

Thanks for the tip, Dave! This looks like a practical design for portable and low-profile operation.

Since it is passive antenna design, I image you would have to re-tune the antenna for peak performance each time you shift frequencies. It looks like the control panel would make this a pretty simple process.

Click here to view this antenna on eBay (partner link).

Post readers: If anyone has used this antenna, please comment with your impressions or contact me with your review.

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Giveaway alert: Joe Carr’s Loop Antenna Handbook

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–UPDATE: A WINNER HAS BEEN PICKED. THIS CONTEST HAS BEEN CLOSED. THANK YOU!–

Lately I’ve gotten a lot of questions from readers about magnetic loop antennas, certainly a popular topic on the SWLing Post. Good discussions underway.

So, when I discovered an extra copy of Joe Carr’s excellent Loop Antenna Handbook on my bookshelf this morning, it occurred to me to share it with you, readers. I think I won this copy at a Winter SWL Fest a couple years ago; it’s chock-full of Joe’s handy tips and solutions to antenna questions and installation conundrums. It’s still in great shape, and I’m sure will find a good home with a lucky SWLing Post reader.

Interested? Here’s how you can participate…

The Loop Antenna Handbook is chock-full of antenna theory and practical construction projects.

If you’d like to participate in this giveaway, here’s how: Simply comment on this post, telling us about your favorite radio! Give us the make/model, and just share a few comments about why you love it above all others.

This can be any radio: a shortwave portable, an SDR, a vintage radio, a ham radio transceiver, a handheld, a scanner, an aviation radio, whatever…or, yes, more than one, if you simply can’t choose.

I’ll select a winner at random on Sunday, April 7, 2019.

This contest is open to anyone, anywhere! I’ll post the prize to the winner directly wherever you are. (Note: Well, if you’re an astronaut on the ISS, I’ll have to send it to your drop box!)

I’ll also plan to compile and publish the full list of radio favorites in a future post…stay tuned for that.

Click here to comment on your favorite radio…

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Building a 20 meter self-tuning magnetic loop antenna

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I’m often asked about what’s involved with building a home brew magnetic loop antenna.

If you’re considering building a passive loop antenna–one designed to both transmit and receive without any sort of receiver amplification–it’s a simple project. With basic DIY skills, a little math, a good variable capacitor, some copper tubing or coax, and a few inexpensive parts, it’s easy to make a passive antenna designed to operate on a given portion of the HF spectrum. It can be an easy two hour build as long as you have all of the parts. There are a number of tutorials for doing this on the web and several books on the topic (one of my favorites is Joe Carr’s Loop Antenna Handbook).

The compromise with a passive loop design is that they tend to have a very narrow bandwidth. In other words, you might have to re-tune the antenna via the variable capacitor even if you only move the frequency 5-10 kHz or so.

Via Hackaday, I recently discovered this innovative self-tuning passive loop antenna design by Eric Sorensen. Eric implements a stepper motor to make tuning adjustments. Not necessarily a beginner’s project, but the principles are straight-forward. He even includes a link to his printed components.

Click here to view Eric’s 20 meter loop antenna project.

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