Tag Archives: PK Loops

Indoor shortwave antenna options to pair with a new SDR

Many thanks to SWLing Post contributor, Chris Freitas, who writes:

“I am thinking of the new RSP1A SDR. Would you know of a good indoor antenna that would work well with it?”

Your antenna question is simple, but the answer is complex!

First off, I think the RSP1A is a great choice as it’ll give you proper exposure to the world of SDR (1 kHz to 2 GHz!)  at a modest price.

Unlike a portable radio of course, your SDR must be connected to a PC, laptop, tablet or some sort of mini computer like Raspberry Pi. This limits your ability to easily try different antenna locations within your home compared to, say, a battery-powered portable radio. It might take some dedicated experimentation and patience.

Indoor antennas are so vulnerable to the radio noise within your home.

If you live in an off-grid cabin with no radio interference nearby, even a simple $1 random wire antenna hooked up to RSP1A’s SMA connector would yield results. I occasionally spend my summers in an off-grid cabin and it’s simply amazing what you can do with a modest setup when there are no man-made radio noises around.

Listening to the final broadcast of Radio Netherlands in an off-grid cabin on Prince Edward Island in 2012.

But how many radio enthusiasts live in an off-grid cabin? Answer: very, very few! Most of us only get to experience off-grid life during natural disasters when the electrical grid has been damaged in our neighborhoods.

The reality of indoor antennas

You’ve told me previously that you live in an apartment in an urban setting, hence you probably cope with a lot of RFI.

When an antenna is indoors, it is forced to function within this RFI-dense environment. Your telescoping whip or wire antenna doesn’t discern between radio noise and your target broadcast signal. Thus, noise can overwhelm your receiver, essentially deafening it to all but the strongest shortwave broadcasters.

And simple, inexpensive portable amplified shortwave antennas? I’ve expressed my opinions about them before. They amplify the RFI as effectively as they do broadcasters.

This is why if you had a means to put a small random wire antenna outside–even if it was simply draped outside a window–it would likely perform better than an indoor antenna. I’m guessing this isn’t an option for you, Chris.

Think loops

A broadband loop antenna (image courtesy of wellbrook.uk.com)

Magnetic loop antennas are a popular topic here on the SWLing Post for a reason: they’re one of the best frontline tools for fighting urban noise. (Here’s a great tutorial/presentation [PDF] describing how mag loop antennas work.)

The compact Bonito Mega Loop FX

While you can build an amplified mag loop antenna (like our buddy, TomL) it’s not a simple project.  Passive single turn loop antennas, on the other hand, are quite easy to build but are narrow in bandwidth (here’s a very cheap, simple passive loop project). You would likely design a single passive loop to serve you on a specific brodcast band and would have to retune it as you make frequency changes. You could build a passive loop antenna for less than ten dollars if you can find a good variable capacitor. Here’s another tutorial.

Commercially produced amplified wideband magnetic loop antennas are not cheap, but they are effective. If you’re a serious SWL, a good mag loop antenna is worth the investment.

Here are a few of my favorites starting with the most portable:

PK Loops

The PK Loop

The most affordable and portable mag loop antenna I own is the PK Loop.  I have the more compact PK Loop C-LOOP-HDSW6-18 (6 – 8 MHz), but Guy Atkins also touts the slightly larger Ham Loop which he finds tunes beyond the advertised 3.5 – 14.5 MHz range.

PK Loops are not as broad in bandwidth as the other antennas I mention below. You will have to retune the loop with any band changes and sometimes even within a specific meter band.

Click here to check out PK Loop offerings on eBay.

W6LVP Loops

The W6LVP Loop Antenna

To my knowledge, the W6LVP is one of the most affordable larger diameter amplified wideband mag loop antennas. We’ve published positive reviews of this antenna in the past.

W6LVP sells two versions of the antenna–since you’re not operating a transmitter, this $250 model would be all you need. indeed, if I were in your shoes, this would likely be the loop I purchase–very cost effective.

Wellbrook Loops

Wellbrook antennas are the staple magnetic loop antenna for many DXers.

Wellbrook loops are manufactured in the UK and have been on the market for a very long time. Their re-engineered Active Inoor Loop Antenna LA5030 would serve you well. At £240.00 (roughly $330 US) plus shipping, it’s one of the most affordable in the Wellbrook line, but over a $250 budget.

Wellbrook makes a number of loops, but since you have no plans to mount this outside, I believe their indoor model would suffice.

Other loop options

There’s no shortage of magnetic loop antennas on the market, but most are pricer than the models I mention above and I know you have a tight budget. Here’s are some models we’ve mentioned on the SWLing Post in the past:

I have the RF Pro-1B and am very impressed, but it’s overkiil for your application (and twice the price of the W6LVP loop).

Fighting urban noise

Even if you build or purchase a magnetic loop antenna, you still need to eliminate as much RFI as you can on your own.

A couple years ago, our friend London Shortwave wrote a brilliant guest post about fighting urban noise. Read through his piece and try to implement as much of his advice as you can.

I hope this helps, Chris! This post is by no means comprehensive, so I hope others will chime in and comment with their experiences. Good luck fighting urban noise and I hope you enjoy your journey into the world of the SDR!

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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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XHDATA D-808: A Shortwave Comparison Against Four Other Portables

When the clouds part and the sun shines during the winter in the Seattle, Washington area, it’s time for a celebration! I decided to take advantage of the mild weather and compare the XDATA D-808 (a real upstart in the marketplace, and a value leader in portables) against a few other radios on a nice daytime signal from Radio New Zealand International, 15720 kHz.

Besides the D-808, receivers compared to each other were: the C. Crane Skywave SSB (complete with stray cat’s whisker on the LCD :^) , the Eton Executive Satellit, the Grundig G3, and a beautiful example of the rare Sony ICF-SW1000T (sometimes called the Sony Shortwave Walkman due to the built-in cassette recorder). My apologies for the lower audio setting on the G3.

The antenna used with each radio was a PK Loops “Ham Loop” antenna, which is advertised as covering 3.5 – 14.5 MHz, but my loop actually tunes approximately 3.2 MHz to 15.8 MHz. I also briefly received RNZI on each radio’s own whip antenna.

I used the 3.0 kHz bandwidth on all the SiLabs DSP radios, and the narrow filter on the G3. The ICF-SW1000T has a single filter, so it cannot be adjusted.

Since the G3 and the ICF-SW1000T have the option of synchronous-AM detection, in the video I cycle through those modes on these receivers.

RNZI on their 15720 kHz frequency is often at a good, program listening level in my local afternoons. Next week I plan to seek out and share videos of the D-808 with weak DX signals from an RF-quiet location on the Oregon coast.

Which receiver sounds the best to you with the external antenna, and which one shines with its own whip aerial? Please share your thoughts in the comments below.


Guy Atkins is a Sr. Graphic Designer for T-Mobile and lives near Seattle, Washington.  He’s a regular contributor to the SWLing Post.

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