"What's New" Reviews
MT® 2001

WiNRADiO AX-31B Planar Antenna

By Bob Grove

WiNRADiO, an Australian company famous for innovative computer-hosted receiving products, has just released their AX-31B active VHF/UHF antenna. Although designed primarily for their own receiver line, the antenna works just as well on any VHF/UHF scanner or other receiver. It is not capable of transmitting.

The planar (flat plate design) enables the 8.5” x 11.5” board to be hung on a wall, or even on a window. A six-foot length of RG-58/U cable terminated with a BNC connector leads the signals to a nearby radio.

Architecturally, the layout incorporates a log-periodic dipole array (LPDA) antenna design etched on both sides of a fiberglass circuit board; an integral, solid-state preamp is part of the same board. The antenna is impedance-matched to the input of the amplifier by an RF transformer.

Powered by the 9-volt battery, the amplifier’s 25 mA current drain assures continuous operation of many hours before replacement is necessary; a super-bright LED will remind you that it’s still turned on! A simple modification, the addition of a resistor, enables the antenna to be powered remotely from an AC adaptor through the coaxial cable.

Claiming a 230-1400 MHz frequency range, we discovered that the unit actually works quite well over a much wider swath of spectrum. Gain is advertised as 20 dB, dropping off as the unit is utilized outside its advertised bandwidth. Technically inclined readers will be relieved to know that the third order intercept point is a healthy 25 dBm, protecting it from generating intermod under most signal receiving conditions.

While the specs show an antenna forward gain of 6 dBi, the small dimensions of the LPDA elements limit its directional response to the higher end of its bandwidth. At lower frequencies it is essentially omnidirectional.

Since the AX-31B is not intended for outdoor use, it’s only fair to compare it with other indoor antennas. We selected a Uniden BC3000XLT hand-held scanner, its factory rubber duckie antenna, and a Condor whip for our test. A synopsis of observations at my indoor location, along with an indication of the best antenna at each sample frequency(*), can be found in Table 1.

The Bottom Line:

We are eternally in search of the perfect antenna: small, wideband, potent, and immune to interference. It doesn’t exist. Signal capture is a function of element size and placement, and active (amplified) antennas require power, generate noise, and are subject to overload problems like intermodulation and desensitization.

But the AX-31B has its niche. Exhibiting decent gain, acceptable noise figure, and high overload immunity, it works well in the upper VHF/UHF land mobile frequencies, and its low profile invites unobtrusive placement next to a wall or window.

It can even be used in a pinch for upper shortwave frequencies -- as low as 15-20 MHz or so -- but doesn’t work much better than a few feet of wire randomly run around the room, and it is just as vulnerable to interior electrical interference from appliances, electronic accessories, and power lines.

Nonetheless, for the new genre of wideband scanners which tune down into the shortwave frequencies, the AX-31B offers significant improvement over the factory-supplied whip, and since those scanners commonly have just one antenna port, the AX-31B can be that one antenna.

While a good rubber duckie like the Condor may work just as well on some frequencies, it is not always convenient to set the radio where the whip works best. By experimentation, the AX-31B can be located at an optimum spot for reception and the cable run to the monitoring position.

There is no substitute for an efficient outdoor antenna. But there are cases where such an installation is impractical or even impossible. Given its few limitations, the AX-31B is a welcome addition to the cadre of listening tools.

The WiNRADiO AX-31B planar antenna is available for $129.95 plus shipping from most WiNRADiO dealers, including Grove Enterprises  (PO Box 98, Brasstown, NC 28902; 1-800-438-8155 or visit http://www.grove-ent.com)

Table 1: A Comparison of Indoor Antennas

NOTE: Results will vary with signal direction and propagation, placement and polarization of the antenna, and location of the installation. Directivity is present at the higher frequencies only, becoming omnidirectional (nondirectional) lower, and will be influenced by nearby metal masses.

PAR AM Broadcast Filter

Strong-signal interference not only plagues scanner and shortwave listeners, but medium wave, tropical band, and 160 meter ham operators as well. Now PAR Electronics has come to the rescue with their new BCST-HPF AM broadcast filter.

As the product code suggests, this is a high-pass filter designed to attenuate medium-wave AM broadcast signals; it is inserted in line with the antenna cable. Equipped with SO-239 bulkhead connectors, it’s ready for attachment to PL-259-equipped coax.

With a razor-sharp cutoff at 1.8 MHz, the high-pass filter has an incredibly low 3 dB attenuation at 1.8 MHz, but a steep 50-80 dB swath is taken out of the medium-wave broadcast band and below. AM broadcasters don’t stand a chance of causing problems with this filter! A handy toggle switch allows the filter to be bypassed entirely.

Does it Work?

You bet! We were bothered by a spurious intermod product right in the middle of the 160 meter ham band coming from two local powerhouse broadcasters. A flip of the switch and it was gone, with nothing remaining but pure, unattenuated 160 meter signals! A low-pass filter BCST-LPF is also available.

PAR MON-3 VHF/UHF Antenna

Other than a new receiver, nothing seems to spark more interest among radio addicts than a new antenna! And PAR’s new MON-3 is worthy of the attention. Using heavy-gauge aluminum elements and stainless steel screws, washers, and nuts, the MON-3 comes as a kit, requiring 15-30 minutes set aside for assembly. Only pliers are required.

Claiming 50-ohm-impedance center frequencies in the 144-174, 430-470, and 800-900 MHz bands, the MON-3 actually receives well outside those bands.

Test Results  

One of the nicest antennas we’ve seen in quite a while is the AOR DA3000 discone, reviewed last year in MT. Since it was still in place in our test fixture, we decided to compare the two. Numbers indicate S units of signals received on an Icom R8500 test receiver.

Considering variables such as different cables and lengths, slight pattern differences, and time delays between switching out the antennas, we considered their performance to be very similar. A user would be hard pressed to choose between one or the other based upon signal reception.

For further information and pricing on these products, contact Par Electronics, Inc. PO Box 645 Glenville, NC 28736-0645. Voice: 828-743-1338 Fax: 828-743-1219 Email par@parelectronics.com

Hamtronics LNK-WB Wideband Preamplifier

It's a universal myth that the best way to hear weak signals is by adding a preamplifier to the antenna line. Preamps almost invariably aggravate reception by increasing front-end-overload problems like intermodulation ("intermod"), recognized by the mixed sounds on several frequencies.

With scanners, intermod often includes the beeping garble of digital paging transmitters, or the voice sounds from two different communications transmissions. The interference frequently contains the music of a local FM broadcaster as well. On shortwave, a common malady resulting from over-amplification is a constant background din of sounds from a myriad broadcasters and strong utility signals.

Often, inexperienced hobbyists will be disappointed after adding a wideband preamp only to hear the background noise ("hiss") increase noticeably, another shortcoming of inappropriate additional gain. And wideband amplifiers have considerably higher noise figures than narrow-band amplifiers, somewhat akin to selecting a narrow-bandwidth filter to reduce wideband hiss on a receiver.

            But there are situations in which a preamp can help: rural locations where all signals are low; UHF and microwave bands where distant signals such as satellites are weak; or on antennas ahead of a long, lossy feedline. Another common use for a wideband preamplifier is in a laboratory environment to boost weak signals adequately to be analyzed with test instruments.

If preamps were the ultimate cure-all, professional receiving installations would simply install a marginal antenna and toss a preamplifier in line, but they don't; they design the best antenna they possibly can, and if additional preamplification is necessary, they choose low-noise preamps with only moderate gain, and add plenty of filtering to block frequencies or bands which contribute to strong-signal overload.

Now that we've characterized the appropriate use of a preamp, let's take a look at a good, affordable, wideband preamplifier from a long-time player in the ham radio market, the Hamtronics LNK-WB. Housed in an anodized aluminum case measuring 3-1/2"L x 1-1/2"W x 1-1/4"D, it is affixed with two female, chassis-mount BNC connectors, and a protruding, 24" length of wire to attach +12 to +15 VDC at 10 mA of current. The negative terminal is the metal case.

Inside the box is a single 2SC2369 low-noise, bipolar microwave transistor, a popular part number designed for just this application, and its supportive bias and isolation components. An "idiot" diode is in line to prevent accidental damage from reverse-polarity power connections – as I've done too often myself!

The preamp provides 10-20 dB gain from about 10-500 MHz, gradually decreasing to around 5 dB at 1000 MHz. It cannot be used for transmitting.

Our Test

The LNK-WB was connected between an outdoor log-periodic antenna and an ICOM R8500 receiver to measure received signals.

Without bandpass filtering to remove strong signals from FM broadcasters and paging transmitters, the LNK predictably generated high intermod products, characteristic of small-signal bipolar transistors. Hamtronics warns prospective customers of this on their web site. Bandpass filtering tamed the unit considerably, and its general performance matched the advertised specifications.

With consideration given to its limitations in a strong signal environment, we judge the LNK-WB to be a good value for general purpose, wideband, small-signal amplification. Hamtronics also offers preamplifiers from 24-470 MHz for narrow-band applications

The LNK-WB is available for $59 plus $7 shipping U.S. from Hamtronics, 65 Moul Rd., Hilton, NY 14468-9535. For information, call  (716) 392-9430 or visit their web site at http://www.hamtronics.com.

Yaesu VR-5000 Scan Fix

Yaesu has supplied the following replacement page to the VR-5000 manual correcting the procedure to be followed for doing a programmable memory scan.

Programmable (Band Limit) Memory Scan (PMS)

This feature, a more refined and useful form of VFO scanning, allows you to establish sub-band limits for scanning. This allows you to monitor only a portion of the wide frequency range of the VR-5000, instead of sweeping the entire spectrum from 100 kHz to 2.6 GHz.

Programmable Memory Scan utilizes a pair of frequencies to establish the upper and lower scanning limits within special memories. Here is the procedure for setting up limited band scanning:

Programming

1.         Press the [F] key momentarily, then press the [PMS(PMS SET)] key to enable the storage of the frequency pair into a PMS memory.

2.         The cursor will be pointing at the “PMS CH” menu option; press the [ENT(SET)] key.

3.         If you want to program the frequency pair into the currently-selected PMS register (shown on the right edge of the display), proceed to the next step; if you wish to choose a different PMS register, press [ENT(SET)], then use the [q(t)/p(u)] keys to select a different memory register number. Then press [ENT(SET)] to move on to the next step.

4.         Rotate the DIAL knob to set the cursor to the “PMS TAG” menu option.

5.         Press the [ENT(SET)] key to enable the programming of the name tag to the PMS memory. To attach an alpha/numeric name tag to the PMS memory, program the alpha-numeric “label” using the DIAL knob and keypad, as described previously; if you don’t want to label this frequency pair register, press the [ENT(SET)] key again.

6.         When you have complete the creation of the label, press the [ENT(SET)] key.

7.         Now it’s time to set up the band limits. Rotate the DIAL knob to set the cursor to the “START F” menu option, then press the [ENT(SET)] key.

8.         Set the VFO frequency to the Lower sub-band limit, then press the [ENT(SET)] key.If you programmed the frequency using the keypad, press the [ENT(SET)] key again.

9.         Confirm that the cursor is on the “END F” menu, then press the [ENT(SET)] key.

10.       Set the VFO frequency to the Upper sub-band limit, then press the [ENT(SET)] key.If you programmed the frequency using the keypad, press the [ENT(SET)] key again.

11.       Rotate the DIAL knob to set the cursor to the “END” menu option, then press the [ENT(SET)] key.

12.       Confirm that the cursor is on the “WRITE” menu option, press the [ENT(SET)] key.

13.       The PMS memory programming process for this register is now completed.

Note: 50 PMS memories are available. You therefore can set upper and lower operation limits on a number of bands, if you like. Each PMS memory register, remember, stores both the lower and upper frequency limits.

Operation (Current PMS Register)

1.         Press the [PMS(PMS SET)] key to initiate PMS scanning in an upward direction.

2.         If the scanner encounters a signal strong enough to open the squelch, the scanner will halt and pause on that frequency. Scanning will resume according to the protocol you selected in the previous discussion.

3.         To change to a different PMS frequency pair, press the numerical keys on the keypad corresponding to the PMS register you wish to use. For example, if you are on PMS register “00” and wish to use PMS register “03,” press [0] + [3] while PMS scanning is engaged. Scanning will begin on the new register without further action.

4.         To reverse the direction of the scan (i.e. toward a lower frequency, instead of a higher frequency), turn the DIAL knob one click in the counter-clock direction or press the [q(t)] key momentarily while the VR-5000 is scanning. To revert to scanning toward a higher frequency once more, rotate the DIAL knob one click clockwise or press the [p(u)] key momentarily.

5.         Press the [V/M(MW)] key to disable the PMS scanner, and return to VFO mode.

By Ian Doyle

For US aviation hobbyists or for those whose interest lies in HF, you may be interested in Flight Explorer Personal Edition. This is a fabulous product which enables listeners to track real-time aircraft flight-planned to/from the USA and certain transoceanic routes to/from the USA. Flight Explorer has been in existence for a number of years and, for just a small subscription fee, it enables the individual to access information usually available only to airlines.

Flight Explorer will run on a “reasonably fast PC” using a standard internet connection (dial up or dedicated). The aircraft data is provided from the Flight Explorer (FE) data center and will provide the user with a real-time graphical image of aircraft currently flying at any altitude over the US (Including Alaska and Hawaii), and US “tracked” aircraft over parts of Mexico, Canada and the Atlantic and Pacific Oceans.

Registering is easy via a secure signup from the Flight Explorer Personal Edition section of Avweb (http://www.avweb.com/sponsors/fe/). After registering, you can download the client software and once payment has cleared you will be sent the install code for the software. Once installed, you will be able to fully access the web page and use the product proper via the user selected ID and password.

Two versions of the software are available; the one for which most monitors opt is Personal Edition, which costs USD $9.95 per month for 10 hours usage, charged monthly to your credit card. This should be adequate for most hobbyists. If, however, you are feeling flush, there is a $250 Professional Edition which encompasses a number of enhancements aimed at the corporate airline or professional user; it has a variety of additional features as well as unlimited connect time.

Using Flight Explorer

Once you have an account and user ID, and you have successfully run the set-up programs and logged onto the site, what can you expect? Well, this is truly an Aladdin’s cave of treasures. Flight Explorer will allow the user to monitor any aircraft which is flight planned in or out of the USA.

As a large percentage of HF aviation listening is done over the Atlantic Ocean, Northern Canada, The Caribbean and South America, the advantages of access to a package like this are obvious. Being able to see graphically what you can hear increases the interest enormously.

When you first log on to the site you will see a picture of the world with every aircraft lodged with the centre represented as a dot. It is, however, possible to click and drag on a particular area, for example, the Caribbean. So if we're listening to the HF Caribbean Net and want to identify a particular aircraft that is providing a position report on HF, simply right click on the aircraft icon and then click “Properties.” The aircraft type, airline, position, height, speed arr/dest airport will all be displayed. If you “tag” an aircraft, this information will be retained as the aircraft moves across the screen.

We may, of course, actually hear an aircraft and wish to interrogate the flight details. Press the horizontal aircraft icon in the top right of the screen; this will clear the screen in readiness for our query. Now press the “Quick Filter Option” and key in the flight number heard. If this is flight planned into or out of the USA it will appear as a dot on the main screen. Ensure that the aircraft you are monitoring does actually correspond to the one are that you can see visually on screen; otherwise the aircraft  may not appear, because of being outside the interrogated range.

Numerous other search/filter options are available in this mode. You can input Flight Numbers, Aircraft Types, or Airport Codes; all aircraft currently in the air with a live flight plan to or from the USA will appear. Again, you must remember to clear the screen after each query. It is also possible to overlay the latitude and longitude coordinates, which is particularly useful over the North Atlantic, Canada and Pacific Area.

One word of caution; in some cases of transoceanic routes beyond radar range, the data provided can appear up to 40 minutes old, as only the last reporting point is provided. Hence, the reason the picture over the North Atlantic consists of rows of dots in vertical groupings. Despite this limitation there are still numerous advantages in using the software.  

Although not relevant to the UK, various overlays can also be added with the additional of beacons, navaids, airways and ATC sectors within the USA. This is useful for monitoring the Caribbean area, where, sadly, aircraft serials do not appear.

Another very useful feature is the “Flight List Look Up.” A list of all tracked aircraft in the system will be displayed, showing aircraft ID, origin, destination, aircraft type, altitude, speed, departure time, ETA, or status for each aircraft. The list can be sorted by any of the criteria just by clicking on the title bar.

Once again, this is a superb product and is bound to be of tremendous interest to the serious HF monitor with an interest in aircraft. Although there has been much criticism of the Internet, there seems little doubt that technology that would have been unthinkable five years ago is now a reality, I feel sure that many readers would agree that such developments will only enhance the future of radio monitoring and the general radio listener!

Editor's Note: This review originally appeared in Shortwave Magazine. The author, based in the UK, uses Flight Explorer to monitor international flights while listening to HF communications. However, the program covers overland flights as well, and anyone  can tune in to tower communications at a large U.S. airport via internet-streamed audio while watching the planes arrive on their screen. Jean Baker also reported on Flight Explorer in Plane Talk, June 2001.