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America's Most e Amateur Dealer,

Standard Frequencies

Dear 73:

" Standard Frequencies/' a short article in September 1965 73 said % . . 1000 cycles {is available) from the telephone company by dialing any local exchange i olio wed by 9945." it should have added "in the New York City area.1' Apparently each Bell Telephone division has a different number for its 1000 cycle test tone. In the 3Vi inneapolis-St. Paul area it is any exchange followed by 409S. Telephone companies are reluctant to reveal the number for fear of overloading the line power-wise, but a Utile serious spade work will turn it up. I was able to compare the Minnesota and New York City tones with a telephone on each ear, and the lones were identical, so apparently they are extremely accurate as to frequency.

Robert Kuehn W0HKF

West St. Paul, Minn,

Dear 73:

The need for well organized traffic nets on the V1IF frequencies is here. One good example of this was the recent blackout in New England, which 1 understand was jhandled quite well by the VHF boys in that area, 1 feel that the amateurs don't realize the importance oir these nets until a crisis hits their area and then it's too late to think about organizing a traffic net. We are a group of well trained individuals who could, given leadership and time. set up one of the finest emergency nets ever dreamed of. I am speaking of the amateur who is on the VHF frequencies. There is a need! Over 300 disasters occur in the U.S. every year and the next one could involve you and your Joved ones. There are a number of these well organized groups in this country, but then there are others, like the North-Sou l h Carolina, Georgia sections that are lacking in emergency groups. Why does this situation exist? One good reason ts the lack of activity-Night after night E can sit at the "rig" and hear no signals for 200 miles. Why can't we get the boys on ihe low bands lo do their local rag chewing on 6 or 2 meters? They are crazy to try what they're doing on ihe 75 meter band; Fll tell you my explanation of the matter* These boys, for the most part, are scared to give it a try- They think that equipment is to hard tn get or build. They also feel that there won't be enough people to talk to, These are good reasons on the surface, but when you get light down to fact* they hold no water. You put forth effort and some determination and these problems wHl no longer exist. If everyone would talk up VHF on the low bands and point out that there are many open frequencies . . . QHM FREE to rag chew on locally, then maybe more people would get on. I have heard too many "slams" against VHF and it hurts. "Sure I'm on 2 meters, I thought everyone was . , . at least alt of lis that have a telephone , , . ha lia," Or you might hear, "There sure is plenty of space on VHF. I was up there and listened for one whole week and heard no one , . . What did I have on 6? . - . Oh, a sixer into my ten-twenty-forty meter vertical. Sure loaded up good though . « i" What is wrong with these supposedly "skilled technicians"? Can't they read the instruction manual that clearly states that a good beam CUT TO FREQUENCY is needed for satisfactory results? We need more positive thinking towards these bands. If we are to use them for what they are best suited for, that being local QSO's and local traffic and emergencies!!! If more oi the low band boys would talk up VHF. or better yel shut their mouths when they don't know anything about them, we would have more activity up on these blessed and peaceful bands . , , or maybe not. Nobody want to be alone. Over the past five years that I have been in S.C.f I have heard many stations come and go on 6 and 2 meters. They don't stay, or they do so little operating that they might as well be gone.

The Greenville VHF Society has proposed a plan that might help matters in this area, We would like to form a loose federation of clubs in this Tri-State area (mainly the ones that are Interested in VHF), and through this organization, form a well organized traffic net to bind the states together. Furthermore, an exchange of information between ihe clubs in the form of bulletins, newspapers and/or membership representation for lectures would keep the union alive. If the clubs would consent, an annual conference could be held at which time officers could be elected and at which, outstanding VHF men (such as yourself) and also representatives of manufacturing companies could come and lecture on VHF topics. This would be up to the individual clubs as the federation does not intend to change any of the basic or political structures of the "local club." The federation would be only a supplement or an aid to them.

Needless to say, it would take a lot of time and a great deal of work, but we are willing to take the first step in this matter only if we feel that others will take their share of the load, 1 have appointed the vice-president of the club to take over the program and to handle any correspondence that there might be. He will be more than happy to receive letters and comment both pro or con. Please address all correspondence to Ron Higgs, WA4ZBV, 106 Clarendon Dr., Clem-son, S.C. 29631.

R. P. GruR-kshank WA4L.TS

President

Greenville S,C* VHF Society

DX Antennas

Dear Paul,

It seems that my article in the April 1966 issue of 73 ("A Look at Antennas for DX/+ p. 68) has stirred some measure of controversy among the DX fraternity. Letters which have come to me in the last two weeks have largely sought to differ with my statements as to the relative merits of vertical and horizontal polarization for long-distance propagation.

Before commenting on the arguments expressed in the letters» though, let's correct an ommission in the text of the article, as published. It looks as though Ihe typesetter completely missed page 6 of the original typewritten manuscript. In the right-hand column of page 71 there appears a sentence which is partially in italics, i his sentence is correct, but the next is not. To correct the article, substitute all oi the following for the incorrect sentence:

The point of this is that an intelligent choice of antenna height consistent with Figs. 1 and 5 and you. pocketbook will get you the best DX signal for the money you have.

Now let's talk about some specific antennas. If you have bought or built the tower that best fits your wallet and radiation angle requirements^ it is time to find an antenna with the most gain and front-to-back ratio you can afford. Keep in mind that the radiation angle is almost completely established by the antenna height, not by the type of antenna, with the mild exception of the cubical quad, which will be discussed later.

Of course the cadillac of DX antennas is the rhombic, with the vee-beam a close second. If you can ailord it, and have the space, pul some up. The design tables are readily found in the handbooks. The average ham, however, must make up his mind between the various types of tower-mounted rotatable arrays. The most popular of these types are the Yagi and the quad, so let's compare the two.

Quad vs. Yagi

Perusal of the reams of information that has been writ I en about the quad and Yagi arrays brings to light some interesting points of difference between the two. Probably the most important difference concerns the radiation angles obtainable from them. For heights greater than one-haIf wavelength Fi^. 4 applies to the quad just like any other antenna. At a height of one-half wavelength or less, however, the quad produces slightly lower angle radiation than the Yagi will. (End correction)

Now in hopes of clearing up the questions posed by those interested enough to write letters, i will reiterate some of the points made in the article.

1* The real interest a DX man has in his antenna is in creating the maximum signal strength at the DX location. If his antenna does this while transmitting, it will also make a superior receiving antenna for listening. So the question resolves itself into this; which polarization produces the maximum field strength at the distant location? The relative merit of an antenna lo produce this distant field strength is evident in its vertical radiation pattern. The important considerations are the vertical angle of the lowest lobe; and the length of the lobe, which represents the field strength generated by the antenna. This disregards gain in the horizontal plane, of course.

2. For equal total antenna heights above average ground greater than one^half wavelength, the vertical and horizontal both produce roughly the same radiation angle at the usual DX frequencies. This assumes that the horizontal antenna is a half-wave dipole, and the vertical is composed of an array of half-wave di poles arranged colli nearly and fed in phase. But Ialthough the radiation angles are about the same), the horizontal icili produce at feast 3 dt> more signal strength in the lower lobe This is because horizontally polarized energy radiated nearly parallel to the earth's surface is more completely reflected than is vertically polarized energy.

3. It is true that continuing to stack collinear vertical dipoles to greater and greater heights will produce lower and lower radiation angles. But due to poor reflection characteristics of the actual average ground for vertically polarized energy, the radiated field strength is simultaneously decreasing in these lower lobes. The net effect is that a simple horizontal dipole, mounted at the same total height, will radiate a stronger signal to the DX location than will an array of collinear vertical dipoles.

4. Let s take a look ai two examples. First* assume a particular ham has a five-eighths wavelength high (about 40 feet) wooden mast for use on 20 meters. He can either run a five-eighths wave vertical wire up the side» or he can mount a horizontal dipole of aluminum tubing on top. The cost would be about the same in either ease. Which, will produce the better DX signal? Consideration of Fiss. 2, ;i and 4 in the original article will lead to the conclusion that the vertical radiation angles from both antennas would be about 23 degrees. This is true, but the fieki strength from I he horizontal dipole will be just about 3 db greater. These statements can be proven (with some effort) through use of Equations 27a and 27b. p. 699 reference 2, and the image concept. This was where the computer came in handy!!

5. Another example is a comparison between the antenna shown in Fitfs, 2d and 3, and a horizontal dipole mounted at one wavelength. Again the total heights are the same, and again the radiation angles will he about the same. But the horizontal dipole wi]l give about 3 db more signal strength at this angle, and would give about 6 db were it not for the fact that the radiation pattern has split into two vertical lobes.

6. The purpose of my article was not to malign the vertical as a DX antenna. After all, many amateurs are having good success with them, and will continue to work their share of the DX. 1 would simply point out that the horizontal is consistently somewhat superior at frequencies above 30 megacycles, where equal total antenna heights are compared. On the 40 meter band the situation is about a toss-up. with possibly a very slight edge to the vertical, since a 40 meter horizontal dipole can't be supported on a single rickety wooden pole, but a vertical made of wire can be run up the side. For the man who is well-heeled, however, the horizontal will probably buy him better performance if he is willing to spend* the money needed to gain the necessary height. On the 80 and 160 meter bands, 1 consider the vertical to be the best choice.

I hope the foregoing has shed some additional light on the DX antenna problem. For those who might be interested in discussing the problem further I am found frequently on the 40 through 10 meter bands (both SSB and CW), and would be happy to schedule a QSO with anyone to exchange views.

Bob Nelson K6ZGQ/5

San Antonio, Texas

P.S.—The DX antenna here is a trl-bander (20-15-10) at 72 feet.

Dear Wayne.

In response to the letter of Paul Glhring (W9JAB), in the March 73, 1 would like to correct what seems to be a misapprehension concerning the state of gravitational theory. While no contemporary physical theory is in totally satisfactory condition, it is not true that "any physical explanation or definition for the gravity field has scarcely been touched on." One might begin his reading on the subject with the basic papers of Einstein and others which were first published in the initial decades of this century- (Now available in Dover paperback). A considerable body of published experimental and theoretical materials exists in the literature from that time on until the present, where the work of Wheeler, Dicke and Feynman (to mention only a few) can be found continuing the same tradition in almost any recent volumes of the Physical Review. Unfortunately, the casual reader will have as much or more difficulty In reading these works as did the contemporaries of Maxwell in the last century, upon first encountering his momentous theory.

Still, 1 would hate to see this discourage the amateur experimenter. The fresh and unprejudiced point of view has nearly always proved fruitful for the progress of our knowledge of the physical universe, and this may be no exception. It may also be that the extreme care needed in observing effects known to be so small is not outside the realms of possibility for to-davfs advanced hams.

Andrew J, Dufuer WA7CXW/6

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