The View from Signal Hill

Semi-Informed Speculation on the
Radio Art

By David M. Upton, WB1CMG

The "Wireless" Trenches

Soon I predict that books describing life in the "Wireless" trade will expose the exploitation of the workers by an unfeeling management and the extreme emphasis which will be put upon being first to the marketplace. Well...maybe not...perhaps Wireless won't prove as exciting as the computer wars outlined in the "Soul of a new Machine" but in the competition for spectrum to field the new gadgets, amateur radio has done well. However, it is not too early to remind these potential "neighbors" that we were here first. Of far more importance is that their systems will have to tolerate interference from amateur radio and this fact of life has a great deal of impact on system design issues. Many of the marginally legal spread-spectrum systems which skirt the bounds of the current FCC rules do not have sufficient margins to tolerate a high-powered amateur set-up nearby. This unsettling fact needs to be stressed in meetings with these concerns when band-planning or RFI issues arise. The FCC has made it perfectly clear that the burden of coping with amateurs is on wireless/spread-spectrum/Part 15/ISM users. It is not that amateurs consistently seek to operate at maximum power just to be a nuisance, but it is a concern that poorly designed ill-suited systems are not allowed to really get deployed in the first place.

It appears that 900 MHz may be re-planned by ARRL to suit the commercial interests behind the "Pinpoint" LMS system which ,unfortunately, has priority at 900 over amateurs who in turn rank above everyone else. Reading between the lines in industrial trademags discloses that the "Pinpoint" people were very pleased with the ruling. This system takes up 8 MHz of bandwidth but the degree of immunity of the system to CW interferers, which would fairly well model most amateur operations, is unknown. If this is any derivative of the poorly-planned systems installed on the West coast, there could be lots of trouble. According to contacts on the West coast, 900 is pretty moribund out there with very little FM repeater activity. Tales of shutdowns at the behest of agents of the system operators or their lawyers are fairly common. This history is particularly troublesome as the companies responsible have been forming alliances to market nationwide. It should be hoped that a "kinder and gentler" approach to resolving RFI issues has been adopted by now.

There exists an unlicensed segment for Part 15 operations in the new PCS(Personal Communications Service) at 1910-1930 MHz where more or less conventional(in the contemporary sense) unlicensed operations may operate. I see no reason why some provision for sharing this segment with amateurs in some fashion is not possible-particularly if the 219-220 MHz experiment goes well. I have therefore inquired of the ARRL to investigate this possibility. If amateur radio is to acquire new frequencies-they are going to have to be researched and fought for now rather than later. The FCC has been dropping subtle hints that little pieces here and there might be made available if the right approach can be found. One of these recent hints concerns a possible band within the 72-76 MHz region as well as somewhere around 40 MHz which has been favorably suggested by NTIA(National Telecommunications and Information Administration) . Realization of a band around 72 or 75 MHz would correct a long-standing gap in the ability of amateurs to conduct propagation studies as well as serve as a bandage over some very painful allocation history.

June QST reports on attempts to "harmonize" European amateur allocations in the VHF spectrum from country to country as well as the ITU Table of Allocations. Although this is currently a solely European effort, the amount of pruning performed there may hold clues to future FCC action here. What seems clear is that the 70 cm band is under tremendous stress and amateur privileges on 23 cm are likely to suffer some cuts. The good news is that 13 cm may be brought into line with the U.S. and that there is some support for a 900 band as well. Amateur satellite operations have been guaranteed an allocation dead center of the available 10 MHz but FM repeaters/ATV/Data users are fighting like mad for their own little pieces of 430-440 MHz pie. Major changes in European bands may affect equipment over here as well since the Japanese factories would have to adapt. Stay tuned for further developments...

As reported in last month's NARC, the author will be speaking at the Manchester convention on "Techniques and Tips for 900 and 2400 MHz" at 2:00 p.m. on July 29th. Those who attended last year's talk at the Eastern VHF conference will probably notice an improvement in the graphics. This is intended as an overview of both ISM bands with regard to methodology and parts. Arrangements for various homebrewium systems have been made to be on display during the talk and after. This is an effort by the locals interested in these bands to find some recruits out there and to show how really easy it can be to microwave. I can promise the good, the bad, and, maybe the ugly but all of the units shown are functional and have been used in actual on-air contacts. I couldn't help but notice QST's spread on SF 13 cm activity recently--perhaps we can show `em a few tricks.

Literature Update

RF Design has published more definitive papers on the art of broadband RF transformers which is sort of a critically misunderstood art in the engineering profession. The first by McClure is a follow-on to work reported earlier in VfSH that Guanella theory can be extended to cover a continuum of possible transformations limited only by the complexities of the structure that one is comfortable in fabricating. Results with up to 7 (septufilar?) transmission lines are shown in various series and parallel interconnections such that discrete predictable impedance ratios are formed between 0 and 1 expressed as fractions.

Using this technique the synthesis of an 8/13 transformer is practical. The second paper more properly deals with the application and modeling of conventional coupled magnetic RF transformers, Ruthroff transmission line types, and Guanella types or equal-delay as they are also known. The author of this article is a researcher in the Royal Navy whom has obviously seen a lot of RF transformer hogwash and misapplication. The article really focuses on the contrasts between the different types and when each is appropriate. Check out the May and June issues for these gems. The annual Directory issue from last year had a good basic article on coding theory for spread-spectrum applications. This was not so mathematical that it could not be understood as many of these presentations tend to be. It comes highly recommended if you can find it.

Dayton Dirge

This April saw a whole new crop of gear previewed at Dayton this year but once again I was loath to find any real technical innovation in it other than how well the manufacturers could copy each other without being sued. As an example of creeping feature spread look at how the "built-in spectrum analyzer" concept has caught on(old timers would insist on calling it a pan-adapter) in HT land. There is still no evidence of an auto-tracking SSB unit that would completely cancel drift and tuning errors which has been rumored to exist for some time now. Since the distortion involved is second-order, DSP should be able to detect an off-tune condition by looking at the spectrum of the signal and driving the tuning of the radio. That is, the radio is off-tune when there exist multiple occurrences of precise harmonics of the lowest frequency signals that are detectable. DSP is usually quite adept at such auto-nulling applications. Such a device would add immeasurably to the enjoyment of HF radio by preserving natural voice attributes without requiring a safecracker's touch at the controls. New emphasis on R&D for the ham market always starts at the beginning of the next solar cycle with that investment bearing fruit typically on the declining side of the peak. Expect really new gear right around the new millennium even though most hams will buy gear well before then. Until that time, unless there is a big swing in market dynamics, the YaeKenComAlIStanco combine will roll merrily along.

ISO--What?

Many firms have been advertising ISO-900x compatibility recently as a suggestion of higher quality practices endorsed by that particular concern. For the record, the ISO standards promulgated by European trade organizations are criteria to audit an organization's effectiveness in documenting its internal production and quality control procedures. None of these standards govern the processes themselves only the documentation of them. ISO-900x acceptance or certification is being touted as helping American companies get the official approval to sell in the European market. It seems odd that in an era when companies are jettisoning bureaucratic ways of thinking wholesale with the creation of the paperless office that along comes ISO-900x . It follows then that a particular company's product may or may not be enhanced by this process and certainly some claims should be regarded with suspicion. It is worthy to note that many of the applicants or awardees of this country's rough equivalent, the Malcolm Baldridge Award, are now out of business.

Quality in a product does not come from following procedures rigidly but by caring about the end result in a personal way. Japanese "Taguchi" methods reflect this understanding in that product tests are compared against a center specified value with gradually tightening limits away from the center value. This method identifies which tests are at the center of the specification unlike the American Go/No-Go +/- 3 sigma limit of spec. center so often applied to most designs. It is possible for a product to exceed the 3 sigma limit and still pass in a Taguchi-model process. What counts is the total distribution of all possible outcomes and how well centered they are on the desired specification. Here the emphasis is to control and model the process so tightly that a huge majority of production fall within a tight distribution about the center. ISO-900x standards will not mandate that this method will be adopted or any other.

They are principally concerned with documentation issues. In the sense that it may force companies to document processes that have been running on "autopilot" for too long it may help but any real change in quality must come from within the companies affected themselves.

It has been a long dry summer at Signal Hill with little going on with radio. 6m and 1200 SSB remain dead and currently e-mail is busted too. Charlotte and, of course, Manchester are coming up soon. Don't forget the VHF/UHF conference in Hartford, CT which has been scheduled for August 25-27th. If unable to attend that weekend, Mohawk ARC(Central MA) is holding a hamfest in Gardner, MA. I didn't get to Deerchester or Contoocook this Spring-maybe I'll do better later this year.