NASWA Journal Columns · Technical Topics, February 2000

Joe Buch, N2JB • P.O. Box 1552 • Ocean View, DE 19970-01552 joseph.buch◊

Technical Topics, February 2000

Collaborative Receiver Design: The RX320 Saga

Hello Dolly

Sevierville Tennessee is famous for three things. One is TenTec. Two are country music legend Dolly Parton. TenTec is the only full-line manufacturer of ham radio equipment and short-wave receivers remaining in the United States. Like Dolly Parton, TenTec often pleasantly surprises us with capabilities that are not immediately obvious at first glance.

Rave Reviews

Back in December 1988, Alan Johnson reviewed the new TenTec RX-320 receiver in the NASWA Journal. Alan’s review introduced NASWA members to a first class radio. While it had no knobs or display, it sold at a price below that of some portable radios. If you have never read that review, I encourage you to go back and read it now. If you are new to NASWA, and you have Internet access, you can read the review on the NASWA web site. This page also has a link to an independent review for Radio Netherlands by NASWA member Tom Sundstrom. If that doesn’t do it for you, check out the year 2000 issue of Passport To World Band Radio for a review by NASWA member Chuck Rippel and Dave Zantow.

All these reviews were very positive. Chuck recently wrote that he ran a side-by-side comparison with a Watkins-Johnson HF-1000A receiver. Here is what he said, “I continue to be amazed at the performance of this receiver. It will literally hear about 80% of what my WJ HF-1000A will….I used it yesterday evening and logged CPBS-1 in China on 4.850 during their sunrise grayline.”

The HF-1000 is considered by most hard-core DXers to be the ultimate in modern receiver design. It should be at a sticker price of nearly $4000. The RX-320 achieves a performance level of 80% of the WJ (in Chuck’s opinion) for a price under $300. Anyway you look at it, the RX-320 by TenTec is a first class radio for an entry-level price.

Open Architecture — A Key to Success

The folks at TenTec took a page from IBM’s playbook. When IBM developed the Personal Computer (PC), they decided to use an open architecture. Anyone was welcome to develop improvements to the hardware and software. Anyone was welcome to manufacture compatible computers whose guts could be interchanged and upgraded to achieve the desired level of enhanced performance. The availability of alternative manufacturers and upgrades led to the popularity of the PC over its earlier era competition. Soon Atari, Commodore, Wang, and even Apple were hanging on by their fingernails while the PC manufacturers were scrambling to keep up with demand.

TenTec designed the RX-320 to work with the ubiquitous PC as a control and display device. This approach saved parts and reduced the size and cost of the radio. But the real kicker is that they decided to make their version of the control software freely available to anyone who wanted to improve on their basic design. The upgrades are now nearing a state of maturity that gives the RX-320 a flexibility exceeding most off-the-shelf radios.

The Internet Facilitates Design

Best of all, the better enhancements have been developed by hams and short-wave listeners who know what they want in performance. In an excellent example of how the Internet can be used for collaborative efforts by people all over the world, SWLs are working together to improve both the hardware and software. Some of them are sharing their work freely with anyone who wants to use it.

Better Software

Foremost among the free software upgrades is a program written by Clifton Turner. By using the Internet, listeners have given Clifton their wish lists. “Make it do this.” “It sure would be nice if it could do that.” Clifton has diligently worked to meet their needs. Chuck Rippel recently wrote, “Clifton’s software really helps put the ‘icing on the RX-320 cake’…. I installed the latest version along with the database yesterday. Clifton has indeed done an excellent job with his software effort. I only wish we had this version in hand when Dave Zantow and I wrote the Passport 2000 review. We will hopefully revisit this issue in Passport 2001.”

Turner’s software provides features only found on the most expensive stand-alone receivers. For instance, the software can compensate for non-linearity in the receiver tuning to provide frequency accuracy within a few Hertz after calibration. You can download the latest version of his free software. The site also has the latest version of the ILG database in a form that can be used by the software.

Brian Denley tells us about a new commercial program. “Dxtra has announced their soon-to-be-released Java version of WorldStation for Win95/98/NT. This is a commercial control program for the RX-320 with sophisticated graphics, functions and database capabilities. You can see more details of this program on the DXtra website.

Better Hardware

A computer can be a nasty noise source. Here again SWLs have answered the call. Alan Matheson in New Zealand says, “I have installed an RX-320 20 metres away from my computer using polymer fibre optic (cable) to totally eliminate electrical connections between the computer and receiver. Result has been a 25-30 dB decrease in computer generated noise level compared to having the receiver near the computer and coupled with shielded serial cable, and about 15-20 dB improvement over the receiver 20 metres away and connected by shielded copper serial cable. Most improvement was between 1 and 15 MHz.”

No Computer Needed

Dave Pearson has developed an accessory to help use the RX-320 on a DXpedition. Dave says, “I have a kit… that will control the RX-320 without a computer. The software can be very easily adapted to provide both a keypad and knob interface to the PC based program. A description and pictures are at: <>. I’ve been using my prototype unit for the last 2 weeks and it’s amazing how much better the whip antenna works with no computers generating noise. I added a function that allows you to use the knob to scan through the stored stations….The microprocessor software can be updated in two ways…it can be removed from it’s socket and replaced (or) a programmer will allow you to download the latest code from my website and program it yourself, without removing the chip….I will also bundle this programmer in the kit as an option. The schematic, PCB layout and program code for the programmer will be on my website for free download.”

Open architecture was a brilliant marketing decision that enabled the PC to succeed where others had failed. TenTec may have a similar tiger by the tail with their open architecture software for the RX-320. And their sync detector is still to come. You can track progress and confer with those on the leading edge of this ad hoc development team via the RX-320 e-mail reflector. Send your blank e-mail to:

Until next time, stay tuned.

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