Category Archives: Antennas

New indoor passive loop antenna for shortwave

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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Kev-Flex Stealth Kevlar Antenna Wire: an incredibly durable wire for field radio

My good friend David Cripe (NMOS) has recently informed me about a new product he’s offering to the radio community via his eBay store: Kev-Flex Stealth Kevlar Antenna Wire. Kev-Flex looks like a superb option for field antennas of all stripes especially since it has an incredibly high tensile strength. It’s available in 75′ bundles, but Dave can also cut custom lengths. NM0S is also a trusted retailer in the ham radio world, so you can purchase with confidence.

Here’s the product description and link:

Kev-Flex is a unique antenna wire manufactured exclusively for NM0S Electronics. The lightweight center core of the wire is made from Kevlar fiber, giving the wire its incredible strength. The Kevlar core is wrapped with six tinned strands of 30 AWG copper. The effective surface of the wire creates an effective skin area capable of handling well over 100W.

The cable is protected from the elements by a coating of UV-resistant black polyethylene. With a total diameter of only 1/16″ (incl. insulation) and a weight of just 16 feet per ounce, the tensile strength 125 lbs allows lengthy unsupported horizontal runs. Kev-Flex is ideal for extremely long LW-antennas and Beverages and is great for balloon or kite-supported antennas. Its low weight and high break-load makes it most suitable for SOTA activations and other field operations.

The outer insulation makes the wire kink-resistant, and its slippery finish makes it ideal for stealth antennas that must be passed through trees or other obstacles without snagging.

This antenna wire is sold in 75 foot long bundles, which is enough for a 40M dipole or EFHW. Two 75 foot bundles would make a great 80M dipole. Custom lengths are available on request.

Specification

– Kevlar fiber core wrapped with six 30 AWG copper strands
– Weather-proof black polyethylene (PE) insulation, 1/16″ O.D.
– Weight: 16 feet per ounce
– Breaking-load: 125 lbs
– Velocity factor 0.97

Click here to view on eBay.

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Giveaway alert: Joe Carr’s Loop Antenna Handbook

–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

Magnetic Mag Loop Antenna Eric Sorensen

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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Amanda to combine art with HAARP

Many thanks to SWLing Post contributor, Eric McFadden, who notes this piece in the Southgate ARC newsletter about our friend Amanda Dawn Christie who is doing a HAARP experiment like no other:

Concordia transmission artist Amanda Dawn Christie will use the world’s most capable high-power, high-frequency transmitter HAARP in Alaska to send art around the world and into outer space using Slow Scan TV

Concordia News reports:

In the shadow of Mount Sanford, surrounded by Alaskan wilderness, you’ll find the most powerful radio transmitter on earth.

On this remote site, scientists use a unique tool called the Ionospheric Research Instrument (IRI) to create radio-induced aurora, also known as airglow. But it’s never been used by a Canadian artist to transmit art — until now.

The IRI’s human-made northern lights inspired interdisciplinary artist Amanda Dawn Christie to create Ghosts in the Air Glow: an upcoming transmission art project that will use the IRI to play with the liminal boundaries of outer space.

“I was so fascinated by these airglow experiments — and the relationship between the ionosphere and radio communications — I felt compelled to create an artwork specific to the site and its history,” says Christie, assistant professor in Concordia’s Department of Studio Arts.

She will be embedding her own encoded SSTV images, audio compositions and propagation tests into IRI experiments from March 25 to 28.

Read the full story at
https://www.concordia.ca/news/stories/2019/03/21/concordia-transmission-artist-launches-a-high-frequency-project-in-alaska.html

Artist made a radio out of a kitchen sink
http://www.southgatearc.org/news/2018/december/artist-made-a-radio-out-of-a-kitchen-sink.htm

Amanda Dawn Christie
http://www.
amandadawnchristie.ca/

https://twitter.com/magnet_mountain

For further info on HAARP HF experiments follow Chris Fallen KL3WX
https://twitter.com/ctfallen

Note that Amanda will share the frequencies and times with us as soon as they are made public. Stay tuned!

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