The Pocket Loop is yet another ingeniously designed product from Kiwa Electronics in Yakima, Washington. It is a twelve inch diameter air core loop attached to a 3 x 4.5 x 2.25 inch box which houses the electronics and controls. One reason the design is so ingenious is that the loop can be collapsed so that the entire unit is only slightly larger than the control box alone (hence the name), which makes the Pocket Loop eminently portable.
OPTIMIZED FOR PORTABLE USE
The Pocket Loop is primarily designed to enhance the reception capability of portable receivers. The frequency coverage is from 530 kHz to 23 mHz in four bands: 530 to 1800 KHz, 1.8 to 7 mHz, 5 to 20 mHz and 18 to 23 mHz. Tuning within each band is accomplished with a front panel tuning knob. The control panel flips up to make access to the tuning knob easier. Band switching is not quite as convenient, however. Switching between the four tuning ranges requires changing the settings of three eight position DIP switches which are located on the main circuit board beneath the front panel. These switches control how the loop elements are combined. There are diagrams on the front panel that illustrate the switch settings for each of the four bands and a stylus for changing the switch positions is attached to the circuit board (along with clips to hold it when not in use).
Since the Kiwa Pocket Loop is designed for use with portable receivers, there are several ways to couple the output of the antenna to the receiver's antenna input. For the frequency range of 530 -1800 kHz, the coupler is placed near the radio's internal ferrite loop. This will require some experimentation, since this location is different for every model of radio. There is a self-adhesive velcro strip to attach to the radio to hold the plastic clip for the coupler once the ideal spot is located. For the shortwave ranges, the coupler slips over the radio's whip antenna for a direct connection to the radio's input circuits. The coupler actually is a "Y" configuration - besides the antenna coupler, there is one leg of the cable that is designed to be placed in either the line out or headphone jack of the radio to establish a ground return path. This connection is vital for best performance.
There are a few others ways to get the signal from the Pocket Loop to the radio. The signal ouput jack from the loop is a RCA phono jack, so a patch cord with the appropriate connector on the radio end can used to connect the Pocket Loop to the radio's external antenna input jack. The potential drawback to this approach is that some radios have non-defeatable attenuation on the external antenna input to prevent overload. If your radio has such an attenuator, it will lower the signal level that is available from the Pocket Loop. The Pocket Loop also includes a cable with a phono plug on one end and stripped leads on the other. This cable can be used with table top receivers that have connections for an external high-impedance (approximately 600 ohms) wire antenna, such as an inverted "L" or random wire. The Pocket Loop cannot be directly connected to the 50 ohm coaxial cable antenna connector on desk-top radios. The output circuitry does not have the capability to drive a 50 ohm input - this was a concious design decision made to minimize the battery consumption of the Pocket Loop. The current consumption of the antenna is rated at 12 mA, so the required nine volt battery will last a long time. There is no provision for using an external power adapter.
Once the Pocket Loop is set up, configured for the desired band and coupled to the receiver (which takes longer to write about that the actual process), operation is straight forward - just turn the unit on and adjust the tuning control for a peak in signal level, either by ear or by the radio's tuning meter, if present. For weak, fading signals, the Pocket Loop contains a built-in wideband radio frequency noise generator which can be turned on to adjust the tuning and then switched off.
For medium wave and long wave reception, a loop antenna can offer the benefit of a directional receiving pattern, which can be put to good use to null the signal of a local broadcaster to enhance reception of a distant station. This effect is usually not possible for shortwave reception, due to way that SW signals are propagated by the ionosphere. I did find that the Pocket Loop did allow me to null out some local radio frequency interference sources - a very handy feature for an indoor antenna.
I used the Pocket Loop with a Lowe HF-150 and a Sony ICF-7600G all set up on the radio desk in my basement shack. This is a very tough location for a test, as signal levels are very low. Signal levels can be increased by placing any antenna closer to the window, but I wanted to see how the antenna performed under worst case conditions. I found that the tuning of the Pocket Loop was relatively narrow, at least when tuning the receiver between different meter bands. However, the tuing of the Loop didn't really need to be adjusted when the receiver was tuned within a several hundred kilohertz range. The tuned nature of the Pocket Loop provides a stage of front-end selectivity (i.e. a preselector effect) to help prevent spurious responses in the receiver. The Pocket Loop was very quiet with no detectable added noise to the signal.
I compared the Pocket Loop to the Sony's built-in whip as well as a Radio Shack Amplified Indoor Antenna (Catalog no. 20-280). One of the tougher test stations I could find was Radio Sweden on 7115 kHz at 0330 UTC. With just the Sony's whip the tuning LED would intermittently light and the signal was just barely copyable. With the Radio Shack antenna, the tuning LED lighted continously, but the signal was buried in noise (this improved with moving the antenna from the desktop to the windowsill). With the Kiwa Pocket Loop the tuning LED lit steadily and the signal was copyable, although not "armchair" copy. So, yes, it does work and work well. Besides the lower noise, the Pocket Loop's advantage over the Radio Shack antenna is its wider low end frequency coverage. The Radio Shack antenna covers 3 to 30 mHz; the Pocket Loop covers 530 kHz to 23 mHz. The Pocket Loop costs four times the price of the Radio Shack antenna, but it is of vastly superior quality, both in design and construction.
If you are looking for a way to enhance the reception of your portable radio, especially if you want an antenna that can travel with the radio, the Kiwa Pocket Loop deserves investigation. It is priced at around $120 and is available from the major SW equipment dealers or directly from Kiwa Electronics, 612 South 14th Ave., Yakima, WA 98902; (509) 453-5492.
Published by permission from NASWA NASWA