Collinear Antenna

/Car/ T. Tburber, jr. W8FX 317 Pop/^r Drive Mi Hbrook AL 36054

's SC-150A 2-Meter Collinear a commercial-quality antenna built to take it

Meters Colinear Antenna

Kreco four-element collinear antenna gives an approximate 6-dB gain on 2 meters; A quarter-wave radiator, three quarter-wave sleeves, and a ground-plane section constitute the antenna's main components.

In the infancy of this writer's amateur radio experience, back in the seemingly prehistoric 1950s, heavy, massive "plumber's delight" beams were all the rage. Indeed, you were "in" if your tower sported an array that appeared to be crafted by no less than a master plumber. 1 was, therefore, fondly reminded of the "good old days" by recent ads showing the line of VHF antennas sold by the Herb Kreckman Company of Cresco PA.

The Kreckman catalog displays a line of antennas for the ranges 25-50 MHz, 72-75 MHz, and 108-470 MHz that is geared for the commercial FM two-way trade. Most of the firm's sales are to installers for taxi cab fleets, police and fire departments, government agencies, paging services, and related applications. For obvious reasons, the antennas furnished these users must be rugged, maintenance-free, and require little or no tune-up or other installation adjustments,

Most of the Kreco antennas are not particularly useful to hams, and they tend to the expensive side due to their exceptional rugged ness. However, I was in trigued by one particular stacked VHF antenna in the catalog, the 50150, which is a four-element vertical collinear delivering a stated gain of about 6 dBT It can be factory-set to any frequen-

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cy within the range 108 to 174 MHz, which includes the two-meter band.

Three versions of the antenna are available, with varying degrees of rugged-ness+ The relatively lightweight (3-1/2 lbs.) SG-150A is built of aluminum and requires a threaded 3/4" support pipe. The intermedin ate-duty SOI 51A is simiiar electrically, but ts made of slightly heavier materials and weighs 4 lbs,; 1" pipe is required for the supporting mast. A third and extremely durable version is the SC-155, which weighs 4-1/2 lbs. and requires a 1-1/4" support pipe. Several brass versions are available for premium installations. (Weights given do not include the weight of the user-furnished supporting pipe,)

I opted for the SC-150A, the lightweight aluminum version, which I thought would be equivalent in construction to typical amateur-grade VHF antennas, and also in the same price

category (cost of the 5C-150A is about $66}, I or-

dered the antenna factory-cut for 146.5 MHz.

After assembling the antenna (which is UPS ship-pable) and mounting it on a length of 3/4" pipe, I found that I now had a plumber's delight of my own (the pipe forms an integral part of the antenna). "rhe radiator itself is a quarter-wavelength of sturdy aluminum rod, which is supported by a special ceramic insulator into which the user-supplied pipe threads, along with the PL-259 connector for the feedline, which runs down the pipe, A quarter-wave sleeve drops down over the pipe at this point, forming a coaxial antenna. Two more coaxial quarter-wave sleeves are used for decoupling and gain-enhancing purposes at appropriate intervals down the mast, and a ring supporting the four quarter-wavelength radials is located at a point down the mast which is six quarter-waves (or 1-1/2 wavelengths) from the feed-point

The antenna performed wellH when compared with my Cushcraft Ringo Ranger Cain claims were not verified, but seemed to be reasonable, and the antenna offered a good match to RG-8/U coax. Particularly impressive was the antenna's obvious physical strength. Though living in a relatively benign climate, II can picture this antenna much more than some defying the elements at a mountaintop repeater or remote base location.

In trying to be objective, ] should emphasize the fact that the antenna must be mounted on pipe. Regular galvanized types are fine, but stay away from aluminum or steel TV mast sections, The antenna feed-point insulator assembly is threaded for 3/4" pipe, and it will not accept an unthreaded TV mast. Also, the antenna's coaxial sleeve sections are designed around the pipe o,d. (outside diameter), which affects the resonance of the cavity between the skirt i d. (inside diameter) and the pipe o.d, I purchased and had threaded a 12-foot length of 3/4" pipe (the minimum required), plus an adapter to 1" pipe and a 3-foot section of pipe used to attach the assembly to a standard TV-type eave mount. All this plumbing set me back nearly $18, which added to the total cost of the antenna

Practically alt of the Kreco antennas use the pipe as an integral part of the antenna. Most models are available in aluminum or brass, and each is equipped with a female UHF connector so that a one-piece feedlme may be used between the antenna and the transmitter, Type N connectors are also avail able. Lightning protection is automatically provided by a gap inside the insulator assembly All models are designed to handle any reasonable power level, being limited only by the power-handling capability of the coaxial transmission line feeding the antenna.

Several particularly interesting antenna designs surface in the Kreco catalog These include a number of low-VHF band shunt-fed coaxial antennas; these boast excellent lightning protection since external surfaces are all at ground potential. A large round cap at the tip of the vertical rods on these antennas conducts electrical discharge down through the pipe and to ground via the tower or supporting structure Two folded ground-plane antennas, one for 25-100 MHz and the other for 108-175 MHz use, are available that offer considerably wider bandwidth than ordinary ground planes; they also afford improved lightning protection by virtue of the grounded radiator element. Several unusual 3-element yagis are also made by Kreco, using folded ground-plane driven elements, Most of the antennas can be retuned to the 6-, 2% or 1-1/4-meter bands, and some are adaptable for 10 meters.

For the "wideband specialist/' for the lack of a more suitable term, the firm also sells a group of commercial discone antennas that boast swrs below 2:1 over an &-to-1 frequency range. Several models are available, including ones for the ranges 30-240 MHz, 100-800 MHz, and 150-1200 MHz. In these models, the disc and cone are not continuous, but rather are fabricated of 12 radials each A note in the Kreco catalog advises that the discone antennas can be furnished for various frequencies starting at 4 MHz!

The company also sells a very modestly priced ($19,95 delivered) 2-meter 1/4A coaxial antenna, the CO-2A, also designed for pipe mounting For more information on this antenna, see the "Review section rn the January, 1981, issue of 73.

All things considered, the SC-150A 1 evaluated represents a good antenna choice It's a bit expensive and heavy for the typical amateur installation, but in those instances where rug-gedness, durability dependability, and freedom from maintenance are paramount, it would be a hard choice to beat. For repeater or remote base use, it looks close to ideal.

For more information, write to the Herb Kreckman Co., Spruce Cabin Road, Cresco PA 18326. Reader Service number 478.B

TS-830S from page 67

Too low and the noise is not eliminated; too high and audio distortion may occur. Once the happy medium is found, the blanker works quite well on pulse-type noise such as faulty power line transformers and automobile ignitions.

A 20-dB rf attenuator is selectable from the front panel It becomes useful when you operate the rig in the presence of strong local signals while still hoping to hear the weak ones.

The RIT control has a ±2-kHz range i here is a separate XJT for offsetting the transmitted frequency

One receiver function leaves me completely cold. This is the i one control, which is concentric with the VBT knob. To my ears, the audio sounds mushy when the Tone knob is set to any position other than full treble The manual has almost nothing to say on this con trol function, causing me to wonder if it was included merely to occupy an otherwise unused control position. I'd like to hear from anyone who has found a use for this control!

The Transmitter

Compared to the receiver, the transmitting portion of the 830S is simple and straightforward. It uses a proven combination of vacuum-tube final amplifiers with solid-state supporting circuitry, The tubes used are a 128Y7 driver and a pair of 6146B finals, both common varieties.

The conventional design of the output stage means that the transmitter must be tuned up, a relatively rare skill these days given the profusion of broadbanded solid-state rigs on the market! Fortunately, a "tune" position on the mode swttch allows tune-up to be performed at reduced power, protecting the final tubes f rom undue wear and tear. Once learned, tune-up ts a 30-second procedure

The speech processor in the830S is an rf clipper with two stages, one in the VBT circuit and one in the i-f. A small front-panel knob allows adjustment of the compression level. This setting is rather critical, with about 10 dB of compression on voice peaks being about right. More than 10 dB of compression results in a !ess-than-pleasing voice quality; Incidentally, when headphones are being used, you can listen to your transmitted audio by pushing the "MONI" switch on the front panel, just to the left of the main tuning dial. 1 fmd this indispensable in properly setting the compression level.

VOX controls for gain and delay are also located on the front panel, with anti-VOX on the rear panel The range of adjustment is wide enough to accommodate almost any microphone you're likely to use with the 8305. A high impedance mike is recommended

The 8305 features semi-break-in operation on CW, with the VOX circuitry and controls performing the task Hams with electronic keyers should be advised that the 830S employs negative keying, with —65 V at the key jack

As the 830S is delivered from the factory, the three new WARC bands are enabled only on receive. Getting the rig to transmit on the WARC bands is a relatively simple procedure, requiring the clipping of diodes on the rf circuit board.

The Manual

Kenwood's instruction manual for the 830S contains all of the basic operating information, a small section on maintenance and alignment, and little else Hams planning to do any serious work on their 830S will be advised to purchase a service manual from Kenwood. The lack of even a rudimentary ' Theory of Operation section in the manual is especially annoying, particularly to anyone attempting to write a review of the rig! The manual does contain a set of small but serviceable schematics, although you may need a magnifying glass to read them

On the Air

On the theory that competition is an excellent test of mac hmes as well as men, the 830S was pressed into service in the CW section of the 1981 ARRL DX Contest The rig was operated, mostly on 20 meters, for 48 straight hours. Since our 830S is not equipped with CW filters, we debated whether it should be used at all. We finally decided to try it, cranking the VBT control to the minimum band width of 500 Hz, in an effort to get the selectivity needed for contesting. The results were very gratifying. Not only did the 830S go the whole weekend without missing a beat, but also it turned out to be a fine CW rig even without the accessory filters. I imagine that dyed-in-the-wool CW operators will opt for the crystal fitters, but even without them, the 830S does a nice job.

One thing becomes clear after you've operated this rig for a while. That is that Kenwood did some heavy thinking about how best to "human-engineer" the IS-830S. Take the knobs on the iront pane!, for instance There are 5 distinctly different shapes and sizes. The result is that your rrund quickly becomes attuned to seeking out the "small, flat knob" when selecting a meter function, or looking for the "tall, round knob" when going for the VB1 This difference in physical appearance is coupled with a very thoughtful layout, in which the most-used controls are placed in the most convenient positions Compared to brand-new radios from other manufacturers, and even compared to the old 820S, the TS-830S gets high marks on human-engineering.

Summary

What we have here is an HF ham rig that is evolutionary, as opposed to being revolutionary, Kenwood obviously wanted to produce a worthy successor to the 820S, and they have done so, with a price tag that is lower than the 820S. The aspects of the 820S that endeared that rig to its admirers have been retained tn the 830S, while more modern receiver attributes have been added and the layout of controls improved a great deal, lfr in these days of the solid-state avalanche, you still feel more comfortable with a pair of nice, friendly 6146Bs, then Kenwood has a radio for you —the TS-830S. It's destined to become an industry standard

For further information, contact Trio-Kenwood Communications, inc„ 111 West Walnut, Compfon CA 90220 ■

PCS-3000 from page 71

rear). High power is adjusted by VR408 and low power by VR407, both near the center of the board Auxiliary offset crystals are near the front, and can be "pulled" to move the offset up or down, via adjacent inductors, !by as much as 15 kHz.

Performance

Of course, all this micro computer convenience is great But how does the unit perform? I connected my new PCS-

3000 to a fixed outdoor antenna and wattmeter/swr bridge, and after getting acquainted with the microcomputer, I ran some tests.

My radio, on imy particular w attmeter, puts out 27 Watts in high power and 6 Watts in low power with a 1.1:1 swr on the antenna. (The PCS-3000 is swr pro tected to the point that you can transmit into an open or short circuit; high swr will no doubt result in lower power output, but you don't have to worry about burning out the final amplifier ) The low-power level is internally adjustable by means of a potentiometer, VR407, in the center of the board on top of the main unit, over a range of zero to 25 Watts.

Other stations reported excellent audio quality, without exception. Realizing that folks sometimes tend to be overly courteous, especially when they know you've just bought a new rig, I pressed the issue. I asked them specific questions, such as "Does it sound tinny or bassy? Is there any background noise or distortion on modulation peaks?' Still, nobody had anything bad to say.

Received audio quality was also superior. I connected my own external speaker up to the rig via the 1/8-inch phone plug on the rear of the main unit. I haven't heard a better FM

rig-

My PCS-3000 uses five Amperes in high power. My supply delivers six Amperes, so this is no problem. A couple of lantern batteries in series probably won't do it, though,

I also conducted tests for microphonics While talk ing to a friend, I literally pounded on the radio and dropped it from a height of a few inches onto the table (which was protected by a placemat!). tn both receive and transmit, there was no detectable noise on the signal, except for the noise in transmit that was picked up by the microphone {"What are you doing to that radio, man?").

Mobile Operation

You'd better get acquainted with the microcomputer before you go out and try to operate this radio while driving. Once you're familiar with it, it's easy and convenient to use; it'll almost operate itself.

Here in Miami, the interior of an automobile can rise to formidable temperatures even in the winter, Would this have any effect on the audio quality? Tests with other stations indicated it didn't, other than to produce intermittent gasps and a rather sleepy sound on the part of the operator.

I made a special point to inquire about alternator whine or ¡ignition noise on the transmitted signal. I've never had any trouble of this kind in the past with previous rigs, so I guess my car is pretty quiet in that re^ spect. There wasn't any of this kind of problem with my PCS-3000- Other stations reported the same excellent audio quality in mobile operation as in fixed operation. What about background-noise pickup? WellH going 55 mph into a stiff breeze with all the windows rolled down and a serrn truck passing me, \ have to confess that other stations noticed quite a bit of background noise, But I was still "solid copy."

The digital "S"-meter, consisting of five red bartype LEDs, is very sensitive A full-quieting signal always lights all five of them. If a signal is so weak that none of them is lighted, it's almost unreadable (Incidentally, even the weakest of weak signals will stop the scan,) The meter reacts very rapidly to changes in signal strength such as "picket fenctng/' No mechanical meter could possibly follow this.

In an unfamiliar area, the programmable band-scan feature is very convenient Vou may want to scan the entire 2-meter I M band, but it is useless to waste scanning time covering a bunch of frequencies you know won't have any FM signals, \ program 145.11, the lowest repeater output frequency in the United States, into memory 7 and 147.39, the highest into memory 8, before going on long trips. The PCS-3000 scans about five channeis per second, which is roughly 25 kHz per second using 5-kHz increments and 50 kHz per second using 10-kHz increments. To cover the above range, the scanner takes one minute and 29 seconds in 5-kHz steps and 44 seconds in 10-kHz steps.

Interesting Quirks

One thing that I discovered, after several hours of operation, is that this radio actually has a hidden memory channel. What's more, it is instantly available at any time, just Nke the priority channel, memory 1, The PCS-3000 remembers the frequency you're on just before you go into memory mode. When you leave the memory mode, you're back on that frequency,

I usually set my rig to 146,52 before I go into memory mode, so that I can instantly go back to this important simplex frequency. Usually, I have 146.52 programmed into memory 7 as the lower limit of the band scan and don't want to duplicate it in memory 1.

If you progrcim the bandscan limits in backwards—that is, the upper

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