| Index | Thread | Archive | Oct-2002 | Archive | Send |
 |
  |
|
   |
|
  |
|
>Value engineering can be a useful approach to decisions about developing >an hf >amateur radio station. > >The classic reference is ?Rockwell "Station Design for DX. ca 1960. ARRL >should stir >itself and commission and up to date version. >Another source I found useful was a series on HF DX by the RSGB around >1995 where >they surveyed leading UK DX operators. >Rockwell took the approach of looking at DX dB per dollar. > >In the matter of antennas for 14-30 mHz the finding was that around 40-45 >feet gave the >best cost vs benefit. Below this radiation angles are too high, above this >costs escalate. >Antenna mdelling programs will show the truth of this. Hi Barry -- I totally agree with your basic point, but as a side-effect, you got me thinking again about the Rockwell articles. Following are some thoughts I jotted down, thinking to post them to the reflector, and then thought maybe I'd just send them to you offline, because they are so incomplete. I'd welcome a discussion on this topic, because I continue to dabble in the cost-effectivness problem. --------------------- I've spent a lot of time thinking about this issue over the last 10 years or so, because I, too, always thought that an update would be worth doing (the Rockwell/W3AFM articles were in QST for September through December, 1966). I finally concluded that it's such a big job to do right that it may not be doable today. Even so, I would encourage people to reread the series today, though I'd stop short of a wholesale adoption of its conclusions. It is fascinating in the light of today's amateur radio, not because the concept of cost-benefit-analysis is outdated, but because our basic understanding of the factors that affect amateur radio systems design has advanced so much. For example, in those days we believed that when it came to take-off angles, lower was always better. Today we have access to tables giving (for many locations) the statistical distribution of arrival angles for signals from different target areas over an entire sunspot cycle. To me, the biggest conceptual contribution Rockwell made was the notion that ALL the main variables in your station are inter-related. Depending on where your existing station stands on the cost-per-dB curves for those variables, the cost-effective choice of where to "find" the next dB can be totally different. For example, if you are running barefoot, then the dB gained by investing in a used KW amplifier come awfully cheap. Once you've done that, if you're running a simple wire antenna or a vertical, the antenna is the next logical target. It's often argued that antenna dB should count twice, but that's another long debate all by itself. You can also get into complex trade-offs, like deciding whether you really need more transmitting gain (on the low bands, for example), or whether a cheap receiving antenna will make the most difference. It all comes down, ultimately, to balance. When you are operating a KW into dipoles, a low triband yagi is tremendously cost-effective. When you're an "alligator" on 160, a K9AY loop may be the best (and cheapest) thing you can do for better results on that band. Pre-decision analysis makes a lot of sense, but it isn't easy. Aside from the old wives' tales and marketing snake-oil that circulate in the amateur community, confusing the decision process, there's not a lot of appreciation of the usefulness of these analytical techniques. It's also a fact of life, at least in the United States, that external factors like local government regulation and the neighborhood impact of RFI can overwhelm the most thoughtful analysis of technical requirements for better station performance. When it comes to antennas, in particular, we may be nearing the point where, for many of us, "put it up and see if it works" may be prohibitively expensive (engineering and permit fees, perhaps litigation). At least, you'd like to have to go through that cycle as few times as possible. Just a few thoughts, Barry, and woefully incomplete. 73, Pete N4ZR -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
This Thread
|
This Author (Oct-2002)
|