Cushcraft R Half Wave Vertical

We all remember the old cliches about vertical antennas, but the problem is that most of them weren't true, I've used vertical antennas with good success over the years and have owned most of the brands on the market at one time or another.

Oh sure, if you insisted on ground mounting your vertical, refused to place it in the clear, and just drove any old kind of ground rod into the soii instead of furnishing decent radials, you were disappointed, ,, and have only yourself to blame. On the other hand, if you placed that vertical at a decent height, provided a set of radials at the base, and took pains to tune and prune it properly, you had a fine antenna that worked its share of DX.

Cushcraft has long been known for its fine line of HF and VHF beam antennas, and there are few of us, indeed, who have not seen or heard them play on the various ham bands Perhaps fewer of us have seen or used their muitiband trapped quarter-wave vertical antennas, and I'm sure that fewer still have really paid sufficient attention to what Cushcraft has accomplished with their new R-3. Believe me. it's a breakthrough!

Let's go back for a minute or two and review what we know about vertical antenna patterns. . particularly the best-known and most popular ver-treat, the quarter-wave ground-plane vertical. .«to establish a basis for discussion of the R-3.

Most hams turn to verticals as space-saving antennas when Ihey don't have room to erect larger arrays such as horizontal dipoles, beams, extended wire antennas of at! kinds, and others that require reasonable (sometimes unreasonable) amounts of real estate to own and operate.

Those who have used verticals with success, including those forced to use them because of space limitations, have discovered that quarter-wave verticals seem to work very weil at close distances and very well at long distances. However, at mid-range distances, verticals often don't seem to work as well as conventional horizontal antennas, The reason for this seeming anomaly is theangieof radiation, specifically the vertical angle of radiation.

In order for the normal dlpoles and other horizontal antennas to exhibit their best verticai radiation angles, they must be placed at least one half wavelength above the ground surface. The vertical antenna, in contrast, exhibits a very low vertical radiation angle even though its boltom end is resting on the ground. Each amateur band has a different optimum vertical angle of radiation for maximum distance transmission. For example, an optimum vertical angle of radiation for a horizontal antenna on the 20-meter band would be about 1015 degrees for th<? best DX, By the time the vertical angle of radiation is as high as 20 or 30

The R-3 half-wave vertical from Cushcraft.

degrees above the horizontal, it has become a mid-range antenna and rather poor for DX. As the frequency becomes higher, the required vertical angle of radiation for best DX performance becomes tower, while the converse is aiso true.

Thus, for best performance as a DX antenna, a horizontal antenna must not only be physically large and take up considerable space, ft must also be high... as most DXers know, the higher the better On the other hand, vertical antennas with their naturally lower vertical angles of radiation tend to be natural DX antennas. (Be patient, readers, we're almost there,)

VHF mobile operators have found that quarter-wave ground-plane verticals while adequate for working close-in stations on VHF, suffer when trying to really reach out. because a large portion of the radiated rf rs still radiated at angles too high for line-of-sight work. The solution to this problem is the use of gain antennas, antennas wtiich are longer than a quarter wavelength at the operating frequen cy and which concentrate radia* tton at low vertical angles. On the HF bands the half-wave vertical, though slightly shorter than the 5/8-wavelength antenna, has an additional advantage: While most of its radiation is concentrated at low angles, it has a high-angle fobe for medium distance coverage. In other words, the half-wave vertical provides good signaf cover* age at virtually all distances from close in to far away.

There is another major advantage of the half-wave vertical. Unlike its relatives the quarterand 5/8-wave verticals, it does not need a ground plane or ground-plane radials to function at Jts best! One of the biggest bugaboos of ground-plane antennas is the need to provide a system of radials or a nearly perfect ground for the return current path. Although the ver-ticat part of the quarter-wave antenna is, in fact, a space saver, the radials required tend to offset much of this advantage. Those of you who have wives, mothers, or neighbors who take pride in their homes and in the appearance of the property (as do most hams, of course.,. ahem) know that radials in the form of wires strung around to the roof edgest adjacent trees, stakes in the ground, etc., are unsightly and inclined to arouse ihe worst in human nature.

Enter the R-3, Here is a vertical antenna without radials of any kind that covers the three most-used DX bands: 10, 15, and 20 meters, The R-3 is a true electrical half-wave vertical radiator on each of these bands. It has two traps which effectively shorten the antenna physically yet permit resonance on each of the bands. Best of all, the R-3 can be tuned to exact resonance at your desired frequency within each of the bands. , remotely, right from the shack!

inasmuch as Peterborough is only a forty-five-minute drive from Manchester, site of the ultra modern Cushcraft manufacturing facility, Bob Cushman and Glenn Whitehouse graciously invited me to pick up the R-3 myself and take a plant tour. After a pleasant and very informative walk around the piant, which included a peek at the antenna test range, the laboratory, and the production lines, I picked up the packaged R-3 in its box. tucked it into my car, and took it home.

Several major groups of components make up the R-3, each in its own container, well protected from damage and almost immune to everything but an intentional effort to destroy. You will find the CTA capacitor/motor unit in its own box, the indicatorycontrol unit in another box, the traps and aluminum parts in the main box, and all of the hardware in a plastic bag,. and I mean tough plastic A complete set of illustrated instructions, with exploded assembly views and parts lisi with picture identifiers, completes the package.

All you need to assemble the antenna is a screwdriver, a small adjustable wrench and/or a pair of pliers, and a tape measure. The base section is assembled first by making up the matching and feed ring and attaching it to the base. Next comes the capacitor box with its internal motor, and finally the traps and aluminum tubing which, when assembled proper-Jy, becomes the R-3.., all 22 feet of it, I was impressed with the quality of the aluminum, the stainless-steel hardware, the correct number and sizes of nuts, bolts, and washers, and the general attention to detail that characterizes this antenna. The instructions are clear and straightforward.

Having learned my lesson long ago to read the inductions first, I spent some time looking at the drawings, reading the assembly steps, and comparing hardware to the Hsts of same.

Wherever a dimension was given, I followed it meticulously, measuring everything carefully to see that it was correct. With the assembly drawings and exploded views, I am convinced that anyone could assemble the R-3. The entire process of making up the antenna took me exactly one hour and thirty minutes. . ready for installation,

: had a chimney mount that used to support my small beam, so I decided to use triat.. together with a five-foot piece of TV mast tubing to which the R-3 base is bolted. If you prefer to mount your R-3 on some other kind of support, it wiif fit over any kind of pipe or mast up to a 2-mch diameter. J also had a suitable length of four-conductor rotor control cable salvaged from the former beam installation, so \ decided to use that for the control box and remote motor hookup. Please note that when you buy your R-3 antenna at your dealer or when you order it by mail, also be sure to order enough four-conductor cable to reach from the point of installation to your operating desk where the control box is likely to be located,

At this point. 1 was ready to attach the coax to the antenna, so I chose the right length of RG-58/U (since 1 run only 200 Watts and dont anticipate using an amplifier) with a PL-259 connector on the end, Cushcraft provides a neat little neoprene sleeve that fits over the coax fitting and also gives you a tube of silicone grease to waterproof the coax connection at the CTA box. 1 would also Tecommend that you tape and waterproof the control cable connection at the connector block..,just to be safe.

A quick once-over and i was ready to apply power The control box did move the indicator needle back and forth across the dial...from below the 20-meter band markings to above the 10-meter band markings, so apparently the capacitor was moving correctly in its box. I returned il to the 20-meter position and decided to try that band first,

My swr meter was connected In ihe circuit, so I applied rf power to the antenna at the low end of 20 meters while I moved the switch to resonate the antenna, i.e., tune it to frequency. Suddenly, the swr began dropping, and dropping.. .and dropping. It fell below 1,1:1! Then, just as quickly, it began rising again, so I knew that I had passed the point of resonance. Unable to resist temptation. I switched back to the point of lowest reflected power, made a quick call, and raised K40AH.

'Five, nine, nine here in Atlanta. OM," came the report. After a brief chat, I moved on, working several US and foreign stations in quick succession, receiving very gratifying reports.

The 15-meter band didn't seem to be so hot, but I tried anyway, figuring that even if í didn't raise anyone, l could at least check out the tuning range of my R-3. Again, with actuation of the switch on the control box, I watched the swr drop further and further. r .and, againr it stopped below 1.1:1! What the hay, as long as I was tuned up on 15, why not call into a dead band? It couidn I hurt. Believe it or not, K4CG answered me and gave a 589 report in Alexandria, Virginia.

The R-3 was beginning to make a believer out of me.

On 10 meters, which was closed, 1 did manage to 1une up as before, with the same results, . .and an swr below 1 5:1 at resonance. You ought to know that the instructions are very explicit about tuning, and they mention that if the antenna can t be resonated to less than 1.5:1 at the upper and lower ends of each band by merely tuning the capacitor through the control box, then you will have to change the length of the antenna slightly. .. all of which Is carefully explained.

1 figure that mine worked at the specified dimensions with no changes from the nominal ones given in the instructions because it was mounted high and in the clear, without the length changing influences of nearby trees, wires, and ground.

To date, t have had an opportunity to use the R-3 antenna on both phone and CW in various parts of the bands and have found it unquestionably superior to my regular quarter-wave trapped vertical In terms of the signal reports that il delivers and especially In hearing signals, Being tunable to exact resonance, it tends to filter cut unwanted portions of the band by exhibiting a high Q factor. I have particularly noticed its ability to hear mid-distance stations as well as DX at the same time and to work equally well on short skip and long-haul communication.

Not having a beam, but having various horizontal and vertical antennas for comparison, t can truthfully say that my R-3 outperforms them all in both received and sent signal reports. As the old saw goes, "You can t work 'em if you can't hear 'em," so the rest is up to me No more excuses for not getting ihe rare ones By the way. that brings up an interesting point: l worked VE1SPI on St, Paul with the R-3 antenna, on 15 and 20. Better still, I got ihem on the ftrst call.,.in itself a relatively rare experience for me.

Is there anything that I didnl like? To be honest, no, there is not. You have to be careful in hooking up the remote control cable, and be sure you correctly identify which pin is which, because it will not work if you don't. Also, you have to be careful in putting up an all-metai antenna of any kind to prevent contact with power lines and the like. I would also highly recommend that you connect a surge protector in your coax line to bieed off accumulated static charge and minimize the possibility of a lightning strike.

To sum it up, then, f have to say that the Cushcraft R-3 packs a powerful punch in its slim and trim length, and I recommend it highly to anyone who needs a good antenna that can be erected almost anywhere without radiais and turn in unsurpassed performance for a vertical.

For more information, contact Cushcraft Corporation, 48 Perimeter Road, Manchester NH 03108. Reader Service number 480.

Jim Gray W1XU 73 Magazine Staff

KTi-20 POWER SUPPLY

A power supply isn't a glamor item. If it does what it should do. suppiy a regulated voltage at its rated current, you should be able to ignore it and concentrate on the device that is being powered. The Kem-Tron Industries KTt 20 power suppiy isn't glamorous and it can be ignored once safely installed in the shack,

The KTI-20 is a 13,8-volt, 20-Amp regulated supply, its 20-Amp rating means that it isn't quite big enough to power a 200-Watt solid-state HF rig, but it wiJi do very nicely as a suppiy for just about any less-current-hungry rig in your shack. The supply uses an LM723 regulator driving four pass transistors and contains a crowbar protection circuit that will shut down the supply if a regulator failure should cause the output voltage to rise above a safe level, The output voltage is variable plus or minus about ten percent around the nominal 13.8 volts.

I've used the KTI-20 in my shack for some time to power my 2m rig and, occasionally, a 160-Watt 2m ampfifier. It has been left running continuously for days on end with no ill effects,The KTI-20 will drive my Mirage B3016 amplifier, but won't drive both the amp and exciter at once. That's not the supply's fault, since the two together draw almost 27 Amps.

It's a shame that this supply wasn't designed 5 or 10 Amps heavier The 20-Amp rating is too large and too expensive to drive a low-power 2m rig and too small to drive a solid-state HF rig. But if your total power requirements at 13+8 volts can be met by a 20-Amp supply, the KTI-20 is a good choice at a price that's aiso a compromise between large and small supplies—$129.99,

For more information, contact Kem-Tron Industries, 1424 £ Indianoia Ave., Youngs town OH 44502. Reader Service number 479,

John Ackermann AG9V Green Bay WE

Continue reading here: Cra Antenna From Comrad Industries

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  • peter
    Why a half wave vertical antenna?
    2 months ago