Amateur Radio 1962 Kg1fr

nr minus 1-5 kc crystal oscillator. High or low sideband is selected by the crystal here. This signal is fed into the balanced modulator V-2t which is modulated with the speech amplifier, ¥2 of V-3 and V& of V-6, The output of the balanced modulator is double sideband suppressed carrier, which is fed into the 9 111c amplifier, Ji> of V-3. Then one side band is filtered out in the McCoy crystal filter aivf further amplified as SSIi voltage through V I-The mixer V-5 converts the 9 mc if signal t■» output frequency 7*2T> mc, with the 16.25 me voltage from the VFO, and its doubler (V-10) and amplifier xh of V-6. The output of the mixer V-f> is amplified through the driver stage V-13, then further amplified thrcugh the power amplifier V-14 and V-15.

The final is a conventional class B clamp tube linear. I his type linear has proven to be nearly as linear as a good triode type amplifier and much easier to drive*

The amplifier's static linearity is adjusted at Ri- Connect a 45 volt battery across U with a switch or key in series with the battery. Apply plate and filament voltage to the amplifier. No excitation. Observe the plate idling current of the. final amplifier. Key the battery across R: and adjust the arm of I{, until the plate current remains the same with or without the battery across Ru Now the clamp tube will be releasing screen voltage to the final so as to keep a constant ratio of screen grid voltage to fixed bias voltage.

The clamp tube linear amplifiers are somewhat self limiting in plate power if the load is not sufficiently heavy, or if over excited. Under this condition the tube will draw screen current and drop the screen voltage which in turn limits the plate current, and saves the tube from being destroyed. However, it will distort.

A screen current meter is useless in this type circuit. A screen voltmeter should be used instead. As excitation is increased, the screen voltage (and plate current) will increase to the point of limiting. Adjust load and excitation until proper plate current is

obtained at the point of limiting. Check for efficiency. It should be not less than G5% at point of limiting- Improper setting of Hi will result in poor efficiency.

The input and output condensers of the pi not nf the final amplifier are Jennings Type (iSLA 45*. The KB*!' mmfd padding condenser across the output condenser Cs is a mica. The plate rt choke is wound on a half inch diameter insulating rod (fiber glass, in this case) of #2(5 manganan resistance wire.

IiF transformers T-l, T-2 & T-3 are tor-roidal bifilar wound shielded transformers.

hey are wound on powdered iron torroid forms from Arnold Engineering Company. The primary of each transformer is link coupled to the secondary. The added tuned circuit give better selectivity.

The VFO coil T-6 is a critical element. A quartz crystal has the electrical equivalent of a iarge inductance in series with a small capacity. rhese two are series resonant at the crystal frequency. By auding inductance in series with the crystal, the frequency of the crystal may be lowered. But this added inductance must be high Q, and the crystal must be very active; otherwise the crystal will lose control and the oscillator will be self excited. This oscillator can be moved more than the 15 kc shown, but the further it is moved, the more it has the characteristics of a self excited VFO instead of a crystal controlled oscillator.

The tube line up and circuit of the VFO, doubler, and amplifier, bring up a large question mark to an experienced eye. However, many hours and much changing of arrangements were done before this was settled on. The best proof is that it works, . . .W6JAT

^Don Johnson, W6AAQ; Rudy Stefenel, W6OQW: Dick CurrelI, K6IHS: Denny Moore, WflfifHP; and several others.

^CabraJ Motors, Im\( 51 Victory Lane, Los Ciatos. aQST Jan. 1961, Surplus Crystal HF Filters. Q$T plan. 1959, Mobile SSR Transceiver, QST Mai, J9ii0, SSI! Exciter Circuits usin% beam lube 7360.

QST Oct, Hi Freq. Crystal Filters SSH.

Lifer No. 6

Dear Wayne*

You would be happy to Jearn that as Lifer Number Six, you have awarded a life subscription to a 73 year old steeplejack presently under contract to install TV antennas on the Empire State Itailding, and who is better known in the trade as "No Belt Johnston/' and finally who has not hud a heart attack in the last six months.

tin fortunately this is slightly in error as I'm presently 27, and rarely climb my 60 foot tower- I became interested in Ham radio whiie studying at Tale University and received my ticket soon after graduation while in the Air Force, i am active on 2 thru 20 meters using partially home-made anil partially commercially made equipment.

As a rate*I FA A Commercial Pilot I believe that I jualil'y for your requirement as a test pilot, because every flight is a test to see what happens when I hit the grouml in what is known as controlled crash/'

Dick Johnston K1QJD

Rotate that Tower

Photos by Edward Vol mare K2EVJ

Full utilization of a tower is realized only when the entire structure is rotated. When the tower is rigidly guyed it is necessary to place all antennas above the tower on rotating tubing. This limits the number of antennas which may be put up and places great demands on the tubing and rotator. To avoid these problems and allow stacked antennas, large ! I-frames, etc., the obvious answer is to rotate the tower. Impossible, you say? It might seem so, but like most antenna projects it is easier than you first think and becomes easier in the doing. If you do some scrounging and rigging you can rotate that presently inert tower.

There are two ways to execute any project of this sort: You can engineer the dickens out of it, make engineering drawings, and add tolerances. It will cost like it too. Alternately, you can fashion it, and diddle as the project evolves* This latter method is the one expounded here, and is the only practical one for the individual with limited resources. In line with this attitude, this article should be read for ideas, with copious references to the pictures. This will not be a description blueprinted down to the last measurement, since your attempt will bring to the project different skills and sources than did mine.

The project divides itself into three parts for consideration: 1. The rotating base, the rotating guy ring, and 3* the wheel holders which attach to the tower. The principle is to guy to the ring in which the tower runs on roller skate wheels. The rotating base is the pinion bearing housing from an old car. A

Greenfield Center New Yorl

1955 Mercury rear end was used here; you use what you can find. In the course of operation of a car this bearing is subjected to tons of force applied in the same manner as the tower bears on it here. The tower's weight appears modest by comparison. The base of 1.he tower was modified to run on the bearing by welding the three legs to a piece of boiler plate. The tower tegs should be kept open to the bottom to aliowT moisture to escape. The center of the bottom of the fiat base was determined, and two concentric pieces of pipe were welded into place. The inner, smaller piece of pipe goes through the pinion bearing to keep the tower from hopping off the base. The larger, outside piece of pipe is selected to run on the face of the bearing. A bicycle sprocket is brazed onto the outer pipe just below the boiler plate tower base. The rotator, a prop pitch motor, also has a sprocket welded to it, and the tower drive is applied through bike chain. The prop pitch motor has its own mount off to one side of the bearing base. The bearing base is set several inches in concrete with threaded rods screwed into the tapped holes in the frame. These project several feet down into the body of the concrete.

The guy ring was made from a five inch high, eighteen inch diameter section torched out of an old hot water boiler which was selected for minimum internal wall pitting. This gives you quite a good circle which your welding source would be driven to distraction or high prices to fashion from flat stock, A top rim was welded into place, leaving a fourteen inch hole for the tower to project through. The inside of this face is the running surface for the roller skate wheels, I suggest that all welding of the ring be done by the electric arc process. It heats the material adjacent to the weld less, and leaves it stronger and less deformed, Small loops of steel rod were bent into loops and the ends welded to the top surface of the ring. hese are the guy points.

To allow flexibility and to avoid weakening the tower, the wheel carriers were not welded to the tower. Three roller skate wheels mounted in fixtures which clamp to the vertical legs take up the vertical component of force. A set of wheels running in the horizontal plane to take up this component was not used in the interest of simplicity. As long as the guy angles are reasonably flat this simplification

does not seem to be harmful. The horizontal force bears on the bolt heads which hold the roller skate wheels in their carriers. The rubbing of these bolts against the inside of the ring might make necessary their replacement every few years. Even so the tower runs quite freely with very liHle binding as long as the guys are kept somewhat loose. They tend to grow taut in cold weather.

The actual wheel carriers are made from slotted and halved pieces of electrician's metallic tubing (E,M.T-)- The portion of the holder which is clamped to the tower leg is half circle of one inch diameter e*m.t« with television clamps brazed to it to go around the tower leg. The wheel holder itself is a short length of tubing cut out at one end to allow insertion of a roller skate wheel The tabs left after the cut-out? or ears, are drilled to hold the bolt which is to be the axle for the roller skate wheel. Short pieces of e.m.t. are hammered into ovals and then brazed into place between the carrier and the tower clamp to complete the assembly. Washers placed between the bolt heads and the wheel holder can serve to take up the distance between the bolt head and its running surface, the inside of the ring. A gap of at least one quarter of an inch should be left between the bolt heads and the ring to allow easy rotation. The bolts used should be good quality steel- The entire wheel carrier assembly is brushed to remove the borax residue of the brazing process, and the entire fixture is given a coat of rust inhibiting paint.

The tower was erected with several sets of temporary guys, and then the wheel holders and rings were installed. Notice the six guy principle used to keep the ring from turning as the tower rotates. When completed, the rotating tower stands ready to have antennas sprinkled up and down it. Credit for the basic concept of tower rotation presented here goes to Jud, K2CBA. . . . K2LZF


I always like the "Staff" articles as they are informa* tive and often call attention to some idea that was presented in a "book or periodical not available here unless it seta purchased. Heaven forbid that. I am magazine poor already,

1 was very much interested iri the new mixer circuit presented in 73 for Oct. *(51 on page '¿2- I must admit I was quite dubious about it but I went ahead and changed my 75A4 1st mixer to a 6BK7I3 using- the idea presented in the article, My voltages were 250 and 75, with a cathode resistor of 100 ohms. The new mixer was quieter, and had more gain according to the s meter and signal calibrator. I estimate at least a 10 db gain over the €BA7, with a lower set noise.

I do not anticipate changing the 2nd mixer as the 6KA7 circuiiiy gives a handy method of controlling the Siit train independently of (he IF stages, and besides, the 2nd mixer isn't very noisy.

To say I am pleased with this new mixer, would be an understatement.

M. C+ Smith W6GMC

INVADER —More exclusive features than any other 1 ransrnitter/Exciter on the market today] Specially developed high frequency, symmetrical, multi-section band-pass crystal filter for more than 60 db sideband suppression —more than 55 db carrier suppression! instant bandswitching 60 through 10 meters—no extra crystals to buy—no realigning necessary. Delivers sofid 200 watts CW and P,E,P. SSB input; 90 watts input AM. Built- m VFO — exclusive RF controlled audio A6C ^nd ALC(limitertype) provide greater average speech power. Wide range pi network output circuit —extremely smooth VOX and anti-trip circuits. Fully TVI suppressed. Self-contained heavy-duty power supply. Wired and tested with tubes and crystals.


HIGH POWER CONVERSION —Take the features and performance of your "Invader*" . . . add the power and flexibility of this unique Viking "Hi Power Conversion" system . , and youVe "on the air" with the "Invader 2000". Completely wired and tested, includes everything you need —no soldering necessary— complete the entire conversion in one evening.

INVADER 2000—Here are alJ of the fine features of the "Invader", plus the added power and flexibility of an intégrai linear amplifier and remote controlled power supply. Rated a solid 2000 watts P.E P. (twice average DC) input on SSB; 1000 watts CW: and 800 watts input AM! Wide range output circuit (40 to 600 ohms adjustable). Final amplifier provides exceptionally uniform "Q'\ Exclusive "push-pull" cooling system. Heavy-duty mufti section power supply. Wired and tested with power supply, tubes and crystals.

Cat. No. 240-304-2-Amateur Net $1229.00

RANGER If —Now — a new version of the popular 75 watt CW or 65 watt AM "Ranger". The "Ranger II" transmitter also serves as an RF/audio exciter lor high power equipment. Completely self-contained instant band-

switching 160 through 6 meters! Operates by built in VFO or crystal control. High gatn audio-timed sequence keying, TVf suppressed. Pi-network antenna load matching from 50 to 500 ohms- With tubes, less crystals.

Viking "Ranger 11" Kit—Amateur Net , , . $249 50

Wired and tested - Amateur Net $359,50


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