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Monitoring Times Reviews

September 2004


ARD25 Data Receiver

DWM "Yo-Yo Tenna"



ARD25 Data Receiver

By Dan Veeneman


            The term 'Software Radio' has become common these days when discussing the latest developments in receiver technology. Instead of hard-wiring a device to perform a specific function, software radios use microprocessors and programmable logic to acquire, tune, and demodulate signals. The flexibility of simply upgrading software allows the addition of new features (and the correction of shortcomings) without having to replace any hardware.

            Four years ago AOR displayed a prototype software radio, the JT2000, which was designed from the ground up to process radio signals digitally. Although that product has yet to be completed, AOR subsequently demonstrated a less ambitious device called the ARD5000, which hooked up to the 10.7 MHz IF (Intermediate Frequency) output of some high-end receivers and used a DSP (Digital Signal Processor) to demodulate various types of signals. Production of this device also appears to be a long way off, if ever.


APCO Project 25 Decoding


            However, earlier this year AOR introduced the ARD25 Multimode Data Receiver, marketed as a stand-alone decoder for APCO Project 25 (P-25) transmissions. Project 25 is a set of standards for digital radio systems, used extensively in the United States by public safety agencies. As these agencies move away from their old analog radios to new Project 25 systems, scanner listeners are forced to find a way to monitor P-25 signals. AOR hopes to address this need with the ARD25.

            The paperback-sized (6 x 4 x 1.3 inches) black box takes a 10.7 MHz IF (intermediate frequency) signal from your receiver and decodes non-trunked, unencrypted P-25 signals. The audio is sent to a built-in speaker or to an external audio device via a 3.5mm mini audio jack. Talkgroups and other decoded data are sent out by an RS-232 serial port, which can also be used to control the device.

            My review package came with the ARD25 unit, an AOR AR8600 AC power supply, a BNC to BNC cable for the IF signal, a 3.5 mm mini-plug audio cable and a 10-page manual. The two-piece metal box has a solid, quality feel to it, with clearly marked controls, plugs and connectors.

            The compact front panel of the ARD25 has the power switch, three LED indicator lights, an AF (audio frequency) gain knob (basically a volume control) and a headphone jack. As you would expect, the "Power" LED comes on when the AC adapter is in place and the power switch is on. The LED marked "P-25" will light when the ARD25 is decoding Project 25 signals. The "Busy" LED will be lit when the unit is receiving signals in either analog or digital mode, regardless of whether it is successfully decoding or not.

            The rear panel offers five connectors: one for the IF from the receiver, audio in and out, a nine-pin male serial data connector and the DC power jack.


Performance Summary


            The ARD25 easily connects to receivers that have a standard 10.7 MHz IF output, including the AOR AR5000 series and AR-ONE, the ICOM R7100 and R8500, and the Yaesu VR-5000. Other receivers may be modified to provide a proper 10.7 MHz IF output, including the AOR AR3000A and AR8600 series.

            Hook-up to any of these receivers is a quick operation. The toughest part will be making sure your receiver is actually putting out a 10.7 MHz IF signal. I tested the ARD25 with an AOR AR5000, which has an external 10.7 MHz IF output on the back panel but requires activation through a configuration menu.

            Besides the list price of nearly $400, the greatest drawback of the ARD25 is its lack of trunking capability. Not only is it unable to following transmissions across different frequencies (trunk-track), but it is also incapable of decoding the audio from transmissions on trunked systems. In my region, in the Washington, D.C. area, nearly all Project 25 systems are trunked. However, there are many conventional (non-trunked) P25 systems including the Los Angeles Police Department and the New Hampshire Department of Safety. The ARD25 works well on these systems, with audio quality comparable to the Radio Shack PRO-96.


Under the Hood


            The ARD25 contains quite a bit of computing hardware, based around three main integrated circuits. First is a Renesas (formerly Hitachi) microprocessor containing a high-speed central processing unit. This chip holds its programming in on-board flash memory, meaning it can be updated after it has left the factory. The second computing device is an Analog Devices Digital Signal Processor (DSP), optimized for performing mathematical functions. As the name implies, it is often used to handle the workload of processing and analyzing digital signals. It is also driven by software.

            Third is an Altera Cyclone Field Programmable Gate Array (FPGA), which is a specialized device that provides custom hardware functions. Those functions are determined by the equivalent of a schematic held in a "configurator." By changing the schematic in the configurator, the FPGA can be changed to perform different functions.

            For a consumer device this is an impressive amount of computational capability, similar to some sophisticated military radios. It is, frankly, overkill for decoding P-25 transmissions. This leaves me wondering what AOR might have in mind for the ARD25 in the future.




            Despite the shortcomings of the current product, the design itself has the possibility of enhancements in the future. Each of the computing chips is controlled by software, which can certainly be updated to provide new capabilities. In addition, an examination of the printed circuit board itself reveals two connectors: a 14-pin "Debug" port and a 20-pin header labeled "Expand."


Bottom Line


            If you're in an area with large, trunked Project 25 systems, my recommendation would be to purchase a PRO-96 or one of the Uniden digital scanners, since the ARD25 won't be of much value. However, if you have conventional P-25 systems nearby and already have a receiver with a 10.7 MHz IF output, the ARD25 is a nice way to add digital capability to your shack. In either case, keep an eye on AOR to see what enhancements they come out with for this potentially very capable device.


DWM “Yo-Yo Tenna”

By Bob Grove W8JHD


            When you’re operating VHF/UHF portable, it’s really no big deal to find an adequate antenna. Resonant elements are short, and a gain antenna doesn’t require vast expanses of real estate. But for the HF ham operator or shortwave listener, a resonant element can easily be 60-100 or more feet in length, and a multiband antenna can impose a daunting challenge. Often, a transmatch (“tuner”) is employed to cancel the reactance of an impedance-mismatched antenna system.

            And what about restricted apartments, camping locations, business trips, or even Field Day? And how about long-distance emergency comms after a natural disaster or other unforeseen event? Wouldn’t it be nice to have a compact HF antenna that folds up to a few inches to fit in a pouch?

            The military has done it in the past with interchangeable elements, inductively-wound elements, or even reeled metal tape measures which can be unfurled to an appropriate length for the band chosen. Perhaps it’s the latter approach that may have inspired this interesting product from DWM.


Multiband Antenna to Go


            The dipoles are assembled around pairs of enclosed, fishing-style reels which resemble a “Yo-Yo,” as first observed by Jeffrey Lauterbach, the son of DWM’s owner, Bill Lauterbach (WA8MEA). Each reel can release up to 40 feet of insulated, stranded, #22 wire; a pair can effect a dipole for 40-meter operation (7 MHz), or shorter for higher-frequency bands up through two meters (148 MHz).

            The basic “Deluxe” pair YYTD-259 includes a pigtail PL-259 male connector for transceivers; the YYTD-PHN is equipped with a 1/8” (3.5 mm) phone plug for popular multiband portables like most Radio Shack, Sony, Grundig and Sangean radios; and the YYTD-RCA provides an RCA phono plug for models like the Sangean ATS-803 and Radio Shack DX-394, DX-440 and some older receivers and transceivers. All “Deluxe” models are $29.95 each plus $7.95 shipping.  

            For multiband operation, the new, four-reel, dual-band, model Yo-Yo-Vee model 4 ($49.95 plus $7.95 shipping) or six-reel, tri-band, model 6 ($59.95 plus $9.95 shipping) may be in order. The multiband pairs of reels are connected to a popular Budwig center insulator affixed with a standard SO-239 female “UHF” connector for transmission-line attachment.

            If you have a transmatch handy, you can trim the VSWR very low, even on lower frequencies than 7 MHz. Or simply use the transmatch with the basic YYTD-259.

            The Budwig insulator also has a center hole to support the dipole and relieve the strain on the deployed wire.


Erecting the antenna


            The reels are encapsulated, not open, to resist moisture intrusion and prevent unraveling. Each reel has a handy, molded loop to facilitate tying it to a support (tree limb, building eave, pole hook, etc.). When erecting both ends of the dipole, you will need to provide lengths of tether cord; these can be used to tie down securing stakes for the poles as well.

            A tie-off tab is provided on each reel for wrapping a turn of wire to keep it from unraveling further once the proper resonant length is established. The reel is equipped with a spinner knob which assists in both deploying and spooling the wire.

            The six reels which comprise the tri-band dipole are colored by pairs, assisting the operator to equalize lengths on each side of the center insulator. Actually, this isn’t really necessary since all three pairs are electrically connected to the same point on the center insulator, but it’s a thoughtful touch.

            While the small-gauge wire may appear skimpy, it is sufficient for both receiving and transmitting (100 watts or so).

            If you don’t have trees or eaves to support the dipole, you will need to provide masts. DWM suggests telescoping lengths of rigid PVC; it’s strong, cheap and lightweight. Try to get it up as high as possible, since a horizontal dipole will react reflectively with the ground, distorting the radiation pattern to favor overhead instead of the desired horizon.

            It’s best to feed the antenna with lightweight RG-58/U coax; larger-diameter, heavier RG-8/U will provide no significant improvement except when in very long runs (well in excess of 100 feet) at HF.

            And one final tip: You may wish to measure off correct lengths for the band(s) of operation, wrapping a small piece of contrasting-color tape at those points, or brushing on a swath of paint. This makes it much easier to deploy the right length of wire in the field.

            For more information including ordering, contact DWM Communications, P.O. Box 87, Hanover, MI 49241; or phone them at (517) 563-2613 (orders) or (517) 563-9022 (business). Email: or visit their website:


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