Longtime readers of this website know I am a die-hard fan of loop antennas. There are many kinds of loops, ranging from simple, passive loops for AM/LW or SW reception to expensive amplified loops of both the tunable and broadband variety such as the Wellbrooks, Pixel, AOR, Belar and others. Although there are many types of loop antennas they all share one thing in common – they respond to the magnetic rather than the electrical component of the RF signal which means they are inherently less noisy than wire and whip antennas. In many cases where other antennas are plagued with radio frequency interference (RFI), loops can be impressive in their ability to deliver a better quality, less noisy signal. Plus, being directional they can be aimed to peak a signal or to help null noise or an interfering signal.

Paul Karlstrand (the “PK” of PK’s Loops) is a semi-retired broadcast engineer who has designed an exceptionally large range of loop antennas, ranging from passive to amplified designs covering AM, LW or SW bands. Some models are designed specifically for use with portable radios to be used via induction (with no electrical connection to the radio). Others are for radios with external antenna inputs such as component receivers. His customers include government and other professional monitoring agencies and broadcasters in addition to hobbyists. He also offers several single frequency pre-tuned loops and will even custom build one for the frequency you specify. To my knowledge no other company offers as many different loop models, so if you are in search of a loop antenna you will probably find just what you need at their website: http://www.amradioantennas.com/index.htm

Description: Paul graciously sent me his most popular model for review, the A-LOOP-TAM, a 14″/36cm model and I must say I have been most impressed with it. It arrived well-packed with a high-quality plasticized one-sheet which covers their various products, instructions and an Australian MW station guide.

This is a model designed for any radio which has a built-in ferrite rod antenna (which includes almost all portable and many table radios) and if you’ve never used an antenna of this type, the way it works may seem a bit surprising. There is no direct connection to the radio. You simply place the antenna near the radio where it radiates its strengthened signals into the radio’s built-in antenna. To get started, tune your radio to a weak signal and aim the radio for best reception. Now place the antenna perpendicular to the radio, either to one side or it, or in front or behind it, and tune the antenna until you hear the signal increase. Now move the antenna around and find the position where it sends the strongest signal to the radio. This position will remain the same for all stations so you only have to do this once. Now as you tune to different stations, rotate the radio and antenna together and tune the antenna for each signal. One optional nicety is to use a Lazy Susan to rotate the radio and antenna together. *See End Note about common mistakes and misconceptions for first-time loop users.

Rear: Select-A-Tenna M – PK’s A-LOOP-TAM Front: Terk Advantage AM – Tecsun AN-200

Performance: The PK’s A-LOOP-TAM unit is very solid and well-made and its ruggedness should make it less susceptible to damage than most of the less expensive loops available.  One feature I like is that, unlike other similarly-sized AM passive loops, the AM band is split into two segments, ranging from 525-710 KHz and from 710 – 1725 KHz, selected by a toggle switch. This means that the tuning control is much less fussy and very easy to peak precisely. Together with what feels like a high quality, smooth-acting tuning capacitor, tuning is very smooth, precise and non-finicky. But the obvious durability of the PK’s loop makes it much more likely to survive the rigors of being packed in luggage – many lower priced loops feel fragile by comparison.

After getting the feel of the A-LOOP-TAM I compared it with several other small passive loops, including the well-known Select-A-Tenna M, Terk Advantage AM, and the Tecsun/Kaito AN100/AN200. I used several radios for these comparisons – the Sangean PR-D7 (because PK’s website uses this model to demonstrate how this loop works and because it represents an average-performing AM portable – Three Stars in the AM Mega Shootout Article), a vintage Sony ICF-2010 (because it is a Four Star radio and has a 10 segment LED signal strength meter), a Panasonic RF-2200 (because it is among the most sensitive (Five Star) portables there is and it has an analog signal meter which shows very fine differences in signal strength, as well as several other portables.

As you can see from the pictures, the A-LOOP-TAM is a big larger than the other loops which range from about 9 – 10”. (PK’s does offer a 10” model, their A-LOOP-MTAM Mini Loop). As expected, the slightly larger PK’s Loop was a bit more powerful than the others but the difference was fairly slight… all the loops provided noticeable gain and improved reception of weak signals on the PR-D7. On the Sony 2010 the 10 segment signal meter occasionally showed one extra LED with the A-LOOP-TAM compared with the other loops, and on the Panasonic RF-2200 the analog signal meter showed the difference a bit more clearly.

Just A Few Of The Many Models Available

As is true of all smaller passive loops, the subjective improvement in reception is usually inversely proportional to the sensitivity of the radio. That is, the more sensitive the radio is, the less obvious the increase in signal level may be. Using the RF-2200 as an example, during daytime tests of weak signals I could see the increase in signal level on the meter but usually there was no obvious improvement in the sound of the signal…the signal meter would rise but the reception sounded pretty much the same. A few signals did show some improvement of course and under extremely low noise conditions, such as out in the wilderness, there would be more signals which would show improvement. But on lesser radios the jump in signal quality was sometimes dramatic. Using the PR-D7 (as in the demo on PK’s site), some signals popped in which were unreceivable without the loop.

The only feature I would like to see added would be some sort of frequency calibrations on the tuning knob to give some idea of where it is tuned…something most loops offer.

Libby Loves Loops!

Conclusion: The PK’s A-LOOP-TAM is an excellent performer in this category. As one would expect it is just a hair more sensitive than the slightly smaller loops I compared it with, but its real strength is its rugged build quality and ease of use with its split AM band which makes fine tuning less critical than on the other loops. Paul Karlstrand is clearly a radio lover and a master of antenna design and his devotion to performance and quality are evident in his products.

Recommended!

Jay Allen

*Common mistakes and misconceptions about passive loops

Nothing frustrates me more than reading an online “review” by someone who says his loop “doesn’t do anything”. Over the years I have seen this comment from time to time, but since passive loops are very simple it is highly unlikely one would ever fail to work and I have never yet seen a defective one. What these comments illustrate is that using one takes a bit of understanding of some radio basics so I will attempt to provide a clear explanation of what you can expect of a passive AM loop. Their effect can range from barely noticeable to dramatic.

First, learning how to orient the loop with respect to the radio can initially be tricky, especially where there are many strong signals. I recommend you try it in the daytime, or if at night, try to find a very weak signal. That will make the antenna’s effect most obvious. If you have a radio with a signal strength meter that also makes it easier but is not a necessity.

Users should understand that, even though these loops provide a significant amount of signal gain, this added gain does not always translate into a difference you can hear – the effect can range from dramatic to non-existent. The reason is that more signal only helps in certain conditions. Generally, the more sensitive your radio is, the less you may hear an improvement with any small loop.  On an average AM radio such as the Sangean PD-D7 which rates Three Stars in the AM Mega Shootout the effect can be night and day. Tune in a barely receivable signal and you’ll find a huge boost when the loop is brought into play. But with super sensitive Five Star radios such as the Panasonic RF-2200, GE SR I, SR II or C. Crane CC-2E there are only a few instances where the improvement will be noticeable, even though the antenna is providing a stronger signal to the radio. Why does this happen? It is because the most sensitive radios are able to deal with those very weak signals and make them sound louder and clearer than on lesser radios, so most reception is limited not by the radio’s sensitivity but by your local noise floor…the amount of background electrical noise present in most of today’s homes. In these cases, increasing the signal level does less good. For more on this read the Combatting RFI Article.

Another factor to consider is that some radios may have their internal ferrite antenna positioned front to back, rather than left to right in the radio. The Grundig Satellit 800 is one of these, and I have a clock radio which also has its internal antenna running front to back. With these the loop must be positioned perpendicular to the ferrite rod, not to the radio itself.