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| Reviews Summary for Comtek 4-Square Systems |
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Reviews: 14
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Average rating: 5.0/5
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MSRP: $319.95-349.95
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Description: Comtek has manufactured the ACB-4 series of 4-Square Phasing Systems since 1990. Incorporating many improvements since 1994, the ACB-4 "Collins" series produces up to 5 dB gain and 20-25 dB Front to Back in a properly constructed 4-Square array. Available from 10 meters to 160 meters in single band models. More information available at www.comteksystems.com
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Product is in production.
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More info: http://comteksystems.com
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write your own review of the Comtek 4-Square Systems.
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OH5JJL
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Rating: 5/5
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Aug 4, 2008 23:59
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Works as advertised
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Time owned: 6 to 12 months
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I have ACB-4 for 20M with ground mounted verticals. It's an awesome product! F/B with DX signals is outstanding 20 dB and F/S is also very good. I like the most quick heading switch - you don't need a rotator to change the direction in just a second. You don't need to climb either.
I have about 50 ground radials per element. I also tested elevated verticals with 4 radials. The gain was about the same but F/B wasn't so good. I suppose the balance between elements wasn't good enough so I'm back with monopoles. I have current chokes in every feedline just for sure.
Installing the radial field is a hard job (thanks to my XYL for understanding) but it's worth it. 4-square arrays are made for homebrewers. You need to build properly adjusted feedlines, radials etc. If you want an "easy" way, put a beam up to a tower.
Jim Miller is a very helpful person and his customer service is good.
By the way, my array is in the middle of tall trees. I haven't had any trouble with them. Maybe the array would work better in a field but I don't want to cut down those trees. I have heard good experiences from other hams with similar installation - don't worry too much the trees.
73 Tuomas OH5JJL
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W9PL
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Rating: 5/5
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Jun 15, 2008 18:54
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GREAT Results!
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Time owned: more than 12 months
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I renewed my acquaintance with Jim K4SQR in 1996, after having heard and worked him (almost 30 years ago now) when he was KZ5JM in the Canal Zone. Before buying my Comtek Systems ACB-4’s, I asked Jim for advice about my planned approach to use elevated radials and low-cost Hy-Gain 18V-S verticals. Jim has always been very eager to help with any questions I’ve had. I installed my Comtek ACB-40 40m and ACB-20 20m 4-squares in August 1996. I also bought the Comtek RG-11/U coax feeder cables. My array elements and radials are elevated (3 radials per element, sloping down from the feedpoint at about 8 feet above ground to typically roughly 1 foot above ground).
My 20m 4-square elements are “stock” Hy-Gain 18V-S verticals (without the base loading coil), about 16 feet tall from the feedpoint to the top. The average length of each radial is only about 13 feet. My configuration with “short” radials provides resonance and low VSWR due to proximity of the lower end of each radial to ground. At the feedpoint of each element, I use a RadioWorks 1:1 balun. The radials are very close to equal-length. The radial lengths were initially adjusted for low VSWR per element and re-adjusted slightly to reduce the “dumped” power, which is 1-3% of the power feeding the array (from 14.0-14.35 MHz).
My 40m 4-square elements are “modified” Hy-Gain 18V-S verticals (without the base loading coil), to which I added a single slightly-sloping wire at the top (about 5 feet long). The modification also involved replacing the upper 2 sections of the 18-V with compatible double-wall sections of aluminum tubing to lengthen each vertical from the “stock” height to about 23 feet and to provide additional strength. The total length (aluminum + wire) of each 40m element is about 28 feet. The average length of each radial is only about 20.5 feet. I used a similar approach for tuning the radials (as for the ACB-20), and the “dumped” power is 1-3% of the power feeding the array (from 7.0-7.2 MHz). Based on my experience, elevated radials much shorter than quarter-wave long work very well (for a configuration like mine).
My results for both 4-square arrays are as good or better than expected, with apparent “gain” of 2-7 dB compared to my “reference” R7 half-wave vertical. The “gain”, F/B and F/S obtained for the arrays depend on propagation conditions, time-of-day and distant station location. The F/B and F/S range from 10-30 dB.
I’ve really enjoyed the ease and thrill of working 20m and 40m DX using my ACB-4’s. Being able to quickly switch antenna patterns during a contest offers a real advantage. I strongly recommend the ACB-4 system, based on my experience and results.
Vy 73 de Paul W9PL
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W8NSI
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Rating: 5/5
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Mar 23, 2008 14:02
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The ACB-20 is great
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Time owned: more than 12 months
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My previous 20 meter antenna was a 1/4 wave ground plane. It was great for dx but you could not null out or eliminate interference (omni-directional).
I bought my Comtek Systems ACB-20 after I read the QST article titled "Rose Garden Array", 3 or more years ago. The article said it performed to near rotary beam specs. While I would not give it that, it has been a totally reliable antenna that works the dx because of its low angle of radiation. Each lobe is wide and overlaps each way so a rotatable array is not missed. Great front to back.
My only problem, in several years since I installed it: diodes in the control box got zapped last summer. Probably from a near lightning strike. They were easily replaced after consulting with Comtek. Turns out that a number of different diodes can be used.
If you want a good directional antenna but cant put up a tower, a 4 Square may be what you are looking for.
I use mine mostly on 14.070 - psk31. I love my 4 Square!
73 de jim w8nsi
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K3LR
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Rating: 5/5
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Mar 10, 2007 08:58
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Comtek is OUTSTANDING!
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Time owned: more than 12 months
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I have been using Comtek products from Jim, K4SQR for over 15 years. In that time Jim's attention to quality and customer service has continued to impress me. I have phased 4 squares for 80 meters (two ACB-4s with 8 full size self supporting verticals). They work outstanding. No problems, lots of gain, great front to back and low dump power. Look at how the K3LR 80 meter scores stack up against the East coast (K3LR is on the OH/PA border) and you will see that the Comtek 4 square is the secret to a super signal. There are lots of Comtek 4 square pictures on the K3LR web site. http://www.k3lr.com I also have Comtek 4 squares for 20 and 10 meters and have the ACB-4's in hand to add 40 and 15 meters this summer! I am also using the Comtek 3 HIGH stacking boxes and Comtek W0IYH chokes too! Every product has worked 100% perfect. You cannot go wrong with Jim and Comtek Systems!
73!
Tim K3LR
http://www.k3lr.com
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K1TL
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Rating: 5/5
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Dec 1, 2005 09:30
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Just utterly FANTASTIC!!
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Time owned: more than 12 months
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I have had the 30m Comtek 4square array now for just over a year. It sure beats my 30m loop. At first I just installed two vertical elements with about ten raised radials. It worked good but needed to add the other two directions.
After staking out the array, which took several days due to the "Rhode Island Nuggetts" we have in the ground and a stone wall, finally found three spots with no rocks and had to bore holes into a huge rock just below the surface of the fourth one to anchor the vertical. The most involved part of installing the array was the radial system. It is a pain but is worth it in the long run. I installed about 70 radials per vertical and used #14 for the radials and #10 for the buss system. I did this in October/November and just three days after completing all the soldering, etc, we had our first snowfall...just made it. It is amazing to hear the JA's coming thru long path where I could just barely hear them with the 30m delta loop.
I installed the dummy load in the shack to monitor "dumped power" which in my case, is about 2% of the output power. There are several large cedar trees nearby but do not seem to affect the system at all. Since I wanted to work into SE Asia, my system is oriented N/S/E/W and not the normally NE/SW, etc direction. Working VK9XG and VK9CG really made my day. Altho we in New England (Black Hole of Ham Radio) have a more difficult time getting into SE Asia, this array seems to work excellent when conditions are working for us.
I would highly recommend purchasing this system if one is thinking about installing a 4sq array.
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VE2TKH
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Rating: 5/5
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Jul 28, 2005 21:08
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Simply the Best!!
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Time owned: 0 to 3 months
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Hello,
I operated 12 days (week #1 and #3) on St.Paul Island CY9SS DXpedition with these excellent antennas on 40M and on 80M. Thanks to my friend Krassy K1LZ who brought them on the island... We worked as far as Oceania and Asia with them from St.Paul which is located in the Cabot Strait between Cape Breton Island and Newfoudland. In case you wonder where it is...
I can tell you that this antenna system simply "Rocks". It do the job and it will do the job again and again. When you go on a band with that antenna system, you can use the well known sentence "Let's Roll". It will give you amazing performance and service. Also, you only need to follow the instructions given by Comtek and it is easy as 1-2-3 to assemble.
Great performance, great product with high reliability! I definitely recommend that product from Comtek to every ham who wants to try it with no fear or doubt.
73
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KY6R
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Rating: 5/5
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Feb 21, 2005 06:00
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Excellent - 20M
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Time owned: 0 to 3 months
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I have a 20M 4 square with 8 raised and tuned radials per vertical. The Comtek 4 square system does exactly what I had hoped / expected it would do. Excellent F/B and S/N. The directionality is right on, and I have tuned my verticals so that there is zero power dumped in the phone band, and less than a watt in the CW band.
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NI1N
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Rating: 5/5
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Jan 10, 2005 10:34
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Fine antenna
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Time owned: more than 12 months
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This is an update and addition to my review from a year ago. In my previous review, I was using a 4 square for 20 meters. Since then, I built a new 4 square for 40 meters, also with 480 4/10-wave radials. This antenna performed very nicely, and since I have also been able to compare it with a 40 meter yagi.
The yagi is an OptiBeam OB2-40 mounted at 92 feet (28m). On the short path (mostly to Europe or Africa), the difference is hard to discern. On the long path (mostly to Asia), the OB2-40 wins by a landslide. But, the 4 square has better bandwidth and the instant direction changing is very nice (especially when hunting multipliers in a contest).
I've been so impressed by these systems that I also built one for 80 meters. I would only have room for 3 verticals unless I wanted to do some major tree removal (the top of the vertical would be in the branches), so for now I'm using the 4 square controller to control 2 full-size 80 meter verticals. This antenna has 240 4/10-wave radials (again, 120 under each vertical).
Wow! It is so nice to have gain and front-to-back on 80 meters! I haven't done many comparison tests with it, but I know it works well when there is a weak DX station and only a handful of people in the USA seem to be able to hear them and I'm one of them :) I don't recall having to wait in a pileup on 80m since this antenna went up, and on an average night one CQ has me working EU stations at contest-like rates until the band closes. During the CQ WW contest, this array played very well even when competing with the big boys in chaotic pileups.
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N4BA
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Rating: 5/5
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Apr 25, 2004 13:05
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Outstanding in all respects!
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Time owned: more than 12 months
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Offered below are some comments and lessons learned from installing and using three 4-square vertical arrays (40, 30, and 20 meters) employing hybrid quadrature phasing couplers from Comtek Systems during the course of the previous three years.
The bottom line first. All 4-square vertical arrays continue to perform as advertised and all of them have exceeded my expectations by any measure! Jim Miller and his team remain superbly attuned to all facets of customer service where the installation and the performance of their products are concerned.
Background and geography. Why a 4-square vertical, and more to the point, why three of them? Simply put, one works with what one has. The QTH is densely populated with trees 75-85 feet tall. It was either remove a sufficient number of them to accommodate a multiple tower installation or "sandwich" the towers among the trees. Both courses of action were unacceptable. Falling trees and broken limbs easily damage expensive tower installations during high winds and storms. In my case, vertical arrays were the solution--hanging wires from trees or installing towers was not.
Antenna site. No special preparations were performed other than to appropriately place the four vertical elements for a given system such that no trees precluded any element from "seeing" the others. I violated this once with the 40M array but it appears to have had negligible effect on performance.
The math and the measurements. Do the math and then do it a second time. Further, do the measurements for vertical element separation on the ground a second time as well. After staking the system out, have another set of eyes check it to include verifying compass readings. It will pay dividends in the performance of the array and in reducing frustration caused by having to shift element locations on the ground once the radial system is installed.
Work the radial system first. Aluminum in the air tends to make hams' hearts beat faster.....but recommend due consideration be given to completing the radial system for the array under construction to include connectivity to other existing radial systems via a buss arrangement. This will preclude repetitive tuning exercises as the "oh, by the way, I think I'll add a few more radials".....or "maybe I oughta tie into the other radial system nearby", ideas begin to percolate.
How many radials? Each of the vertical elements for the three arrays has 90 or more radials on the ground -- 60 radials will work in an outstanding manner....ok, so I "overachieved" this part of it somewhat. The radials consist of both #14 insulated solid and stranded copper wire locally purchased. Buss lines are either #8 or #10 solid copper wire. Initially, elevated radials were used for the 20M array. The array performed as it should but the ground radial system was installed subsequently. This reduced the rearrangement/breakage of the elevated radial system by our local four-legged "critters".
Weatherproofing the relay box. An inexpensive mailbox of appropriate size mounted on a shortened 4" x 4" x 8' treated post dug into the ground makes an excellent weatherproof container for housing the hybrid switching matrix. An appropriately sized opening cut into the bottom of the mailbox affords easy access for the cables and the control line. Caution should be exercised in cutting the opening in the bottom because the metal is quite sharp. An application of paint will allow the mailbox to blend with the site location if necessary. Incidentally, the modified weatherproof container also has space to store a small dummy load for the system if monitoring in the shack is not an objective.
Why would I build another 4-square vertical array?
-- Reproducible performance from band to band.
-- No climbing - easy to repair if required.
-- Storm proofing - all vertical elements from all three arrays were removed and stored in approximately 30 minutes prior to Hurrican Isabel blowing through this area.
-- Virtually instant directional switching. It's a real plus to drop an S9 or greater signal into the noise. Conversely, it's a pleasure to work DX stations with consistent armchair copy.
-- Most materials/hardware tend to be locally available. A reasonably stocked junk box is of considerable assistance.
-- Extradordinary technical expertise is not required - I consider myself a "user" and a "tinkerer", not an engineer!
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WZ7I
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Rating: 5/5
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Apr 24, 2004 19:47
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Quite satisfied with 80 M array
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Time owned: 6 to 12 months
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Well, this system has been in use one winter season so I think I know enough to comment.
Last summer I installed a 4 square array of Hygain Hytowers. (for review see http://www.eham.net/reviews/detail/2238 ) I used the Comtek 4 square phasing box and Jim’s premeasured phasing lines. This array has 60 radials per element with the all the joints where the radials cross each other brazed with copper / phosphorus rod. The array is 500 feet from the house and is fed with LMR-600 cable.
I had a 40 M 4 square array at another QTH with a phasing box made by another manufacturer that did not seem to work quite as well. I fussed and fussed with the 40 M array and was never entirely satisfied. I decided that I would just install this Comtek array and use it without worrying about it. We were careful in its installation but not compulsive. There are some trees that are probably too close but I don’t want to cut more of them.
Some of my acquaintances have questioned the investment. I needed to use a contractor to do most of the installation so the cost was in the ball park of a 2 element yagi and guyed tower. But, I live on a wooded lot where towers are limited to 55 feet. In addition, there is very little that can go wrong with this array. I don’t have to climb to maintain it. There are no mast bearings to bind when the wind blows and there are no guy wires for trees to fall on. Low maintenance and reliability are more important to me than ultimate performance.
But how does the array perform? I am entirely satisfied. It brings me real joy. I can make QSOs that would be impossible with a dipole. The gain helps to hold the circuit longer when conditions degrade. Often, the big advantage is the lower noise floor that a directional antenna gives.
Even if I relocated to an area that did not limit tower height I would put up another Comtek 80 M four square with HyGain HyTower elements.
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