Tag Archives: AM Antennas

Giuseppe discovers his homebrew rotating ferrite antenna works amazingly indoors and nulls RFI

Many thanks to SWLing Post contributor, Giuseppe Morlè, who writes:

Dear Thomas,

This is Giuseppe Morlè again. First of all, Happy New Year to you and to the whole SWLing Post community! I’ve been continuing the tests on my “T Ferrite” antenna for medium wave and the 160 meters ham meter band.

I tried the antenna inside my shack listening to Rai Radio 1 from Milan Siziano, about 800 km from me, on 900 kHz in the early morning after sunrise. The antenna, despite being inside, proved to be perfect for the cancellation of the electrical noise that I had around me.

Disconnecting the antenna from the receiver–a Sangean ATS-909–the noise occupied everything without being able to listen to anything. Putting the antenna back, the noise disappeared completely making the modulation re-emerge, with a weak signal, it was already day, but with good understandability.

The antenna, as I described in another article, is composed of 2 ferrites 12 cm long each, bought at ham fests, tied together with insulating tape.

For the two windings, I used a small section of cable used for telephone systems that is rigid enough to model perfectly on the ferrites–43 turns for the primary and 3 turns for the coupling link to the receiver. The variable capacitor is 850 pf.

I should mention that the magnificent W1VLF channel was my original source of inspiration for this antenna.

Check out the following video:

Click here to watch on YouTube.

That is amazing, Giuseppe! We often think of magnetic loops as the only choice for coping with urban noise and RFI, but ferrite bars–especially configured like yours–are a brilliant tool for indoor low-band listening. Thank you for sharing! We love your experiments.

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Giuseppe’s homebrew rotating ferrite antenna

Many thanks to SWLing Post contributor, Giuseppe Morlè (IZ0GZW), who writes:

Dear Thomas,

I’m Giuseppe Morlè (IZ0GZW) from Formia, on the Tyrrhenian Sea, in Italy .

I built this simple rotating directive ferrite antenna for medium waves and the 160 meters ham band.

Inside the tube there are 2 ferrites with 43 cable windings and 3 for the coupling link that goes to the receiver.

In this video the test as soon as I assembled everything …

In broad daylight, it was 12.00 local time, you could hear well over 2000 km.

The antenna is very directive and perfectly manages to separate several stations on a single frequency.

The pipes are in plastic for plumbing use (PVC), I bought only that one, 5 Euros, the rest is all recycled.

I wanted to share this simple and very functional project of mine with the SWLing Post community.

Thanks and I wish everyone a better year.

Greetings from Italy.
Giuseppe iz0gzw.

Thank you, Giuseppe! What a simple, effective antenna project. I like how you’ve invested so little and recycled parts from other projects. I also love your view there looking south over the Tyrrhenian Sea! What a great place for radio.

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Radio World: History of Directional AM Broadcast Antennas

Many thanks to SWLing Post contributor, Marty, who shares the following article by John Schneider in Radio World:

In the early years of AM radio broadcasting, all stations utilized non-directional antennas. Most all of these were wire antennas suspended between towers or buildings. Interference, especially at night, was severe. An interfering signal of 5% or less in signal strength was enough to disrupt reception of the desired station, and if the frequencies of the two stations were slightly separated, there would be a heterodyne beat note. As a result, only a few widely-spaced stations could operate on each of the AM broadcast channels in the entire country at night. This limited the number of stations that could coexist to about 500 nationwide, with many of them sharing time on a single frequency.

As antenna technologies were developed and improved in the early 1930s, a few progressive stations began experimenting with multi-element directional arrays. This approach offered two attractive benefits: 1) It could reduce radiation towards other stations on the same or adjacent frequencies, permitting more stations to share a frequency; and 2) a broadcaster could direct more signal towards the desired coverage area, and away from wasted areas such as open water in the case of coastal stations.

WFLA-WSUN

The first known use of a directional antenna was by a pair of stations in Tampa/St. Petersburg, Fla. In 1927, the Clearwater Chamber of Commerce acquired station WGHB and changed the call sign to WFLA. A companion station, WSUN, was operated by the St. Petersburg Chamber of Commerce. The two stations shared the frequency of 900 kHz, broadcasting on alternate evenings to promote tourism and business opportunities in their respective communities. In reality, they operated with two station licenses, but there was only one transmitter and one antenna.[…]

Click here to to continue reading the full article in Radio World.

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External Ferrite Antenna by playloudfm

Posted by SWLing Post contributor Troy Riedel:

I just noticed something on eBay.  Seller “playloudfm” based in Greece (100% feedback rating), the first to offer the high gain external ferrite antenna for the Tecsun PL-360/PL-365/County Comm GP5, has a new offering:

From the seller’s listing:

– Frequency: 530Khz – 1710Khz
– Tunable
– Passive, No external power or battery needed
– Wireless connection to AM Radios
– Plus a low impedance output 3.5mm mono plug for 50 ohm scanners
– Improves Sensitivity and Performance of your AM Radio Receiver for AM Band Dxing!
– Very small and lightweight, perfect for traveling antenna

This AM antenna can be used in two different ways
1) you can simply attach it near your AM radio internal ferrite antenna – wireless connection
2) use a 3.5mm cable to get a low impedance output for use with 50 ohm scanners

Use tuning knob to get the maximum signal

RFA200

 

Have any Post readers bought and used this?

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A follow-up review of the PK Loop C-LOOP-HDSW6-18 antenna

In 2016, I purchased portable shortwave magnetic loop antenna designed and built by Paul Karlstrand in Australia. I posted a “preliminary” review of this antenna in 2016 and since then have taken this loop on many travels.

SWling Post contributor, Ron, recently noted that Jay Allen reviewed one of Paul’s inductively-coupled mediumwave magnetic loop antennas. Jay gave it good marks on performance as it compares favorably with the Grundig AN-200, Select-A-Tenna M, and Terk Advantage AM–even having a performance edge due to it’s larger loop diameter. (Note that Paul makes a number of loop sizes–click here to download PDF of catalog.)

In Canada last summer, I used the PK Loop on a number of field radio listening sessions.

But what really sets the PK Loop apart from its competitors is its durability. PK’s Loops are built to be incredibly rugged. I routinely throw my PK Loop antenna in bags/packs and–unlike most of my other radio components–never worry about how it’s padded or protected. There’s little to damage unless you’re intentionally abusive to this antenna. My Grundig AN-200 antenna, on the other extreme, has exposed coated wires around its loop that I’m constantly concerned about harming in transit.

Following up…

Ron’s message reminded me that I never followed up after posting a preliminary review of the PK Loop C-LOOP-HDSW6-18 in 2016.

Shortly after publishing the review, I had a fantastic opportunity to evaluate how well the PK Loop would perform in a typical hotel room. My buddies Eric (WD8RIF), Miles (KD8KNC) and I stayed overnight in a hotel on Wright-Patterson Air Force Base during our mini National Parks On The Air DXpedition.

My Elecraft KX2 connected to an external random wire antenna.

The hotel room was indeed dense with RFI.

We hooked my Electraft KX2 to both the PK Loop and to a simple random wire antenna.

Without a doubt, the PK Loop was much better at mitigating radio noise than the wire antenna we hung on the inside of the hotel window.

Unlike most modern hotels, however, this one actually had operable windows, so we tossed the random wire out the window and made another comparison. In this case, the external wire antenna consistently outperformed the PK Loop, no doubt because it had the advantage of being outside the radio noise cloud within the hotel’s walls. It goes to show that outdoor antennas–even if simply hanging from a room window–will almost always outperform comparable indoor antennas.

A late evening listening session on the condo balcony.

Last summer, I also spent two months in a condo near Québec City. The condo was dense with RFI–the PK Loop made the experience much more bearable.  The loop couldn’t completely eliminate all of the persistent wideband noise, of course, but it did reduce noise to a level that I could enjoy some of my favorites like RRI, VOG, VOT, REE, WRMI, RNZI and even weaker stations in North America like the BBC and DW.

Even the shortwave version of the PK Loop can null out QRM to some degree by rotating the loop perpendicular to noise. I became quite adept at this by the end of our stay.

Summary

Since I purchased the PK Loop, it’s been a constant travel companion and I highly recommend it. I don’t believe you’ll find a more durable or effective portable mag loop antenna on the market.

PK Loops are built by Paul Karlstrand in Australia who has a stellar reputation with his customers. For those of us living outside Australia, there will be additional shipping costs, but they’re negligible and Paul has been exporting these loops for many, many years. I believe I received my loop within a couple of weeks of ordering it.

Click here to view a PDF catalog of Paul’s loops and products.

As an added convenience, Paul also has an eBay store where he sells the following antennas:

This year, I plan to purchase PK’s largest mediumwave loop, the model HDXLTAM that boasts a 20″ diameter. Please comment if you have experience with this loop or any of Paul’s loops!

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