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| Reviews Summary for Comtek 4-Square Systems |
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Reviews: 16
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Average rating: 4.8/5
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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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More info: http://comteksystems.com
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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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W4USA
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Rating: 5/5
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May 10, 2008 14:51
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wow
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Time owned: 0 to 3 months
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Jim is the customer service King. Great product and good advice. I worked several months on the 4 square for 80 meters. This is not a project for the normal ham. It is also a test to see how much your wife loves you :). I used top loaded 35 foot verticals. They had about a 30Khz jump when phased. The Comtek system worked like a champ. With the loaded antennas I only have about 150 Khz but dump about 3% on center. I have 44 antennas here and I hear things on the 4 square that I can't hear on any other antenna.
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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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N4OGW
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Rating: 2/5
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Feb 14, 2007 11:55
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Hmm...
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Time owned: 3 to 6 months
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I recently finished installing an 80m four square using the Comtek box and 4 1/4-wave ground mounted wire verticals.
I first planned to use only two of the verticals as a 2 element array, as I had a reasonable ground system (about 45 1/4-wave radials so far) for those two elements. After connecting everything, it became apparent that something was very wrong. I checked inside the Comtek box and found the problem right away: the coax connectors were not soldered to the circuit board.
I soldered the connectors to the board, but still couldn't get the array to work right. The least dumped power was about 25%, and not at the right frequency (way too high). The input swr was also in the 2.5 - 3:1 range. I figured I had an interaction problem with the tower in the center of the array, and continued on the ground systems for the other 2 verticals.
Once I got all 4 verticals built, it still didn't work. Very high dumped power, bad SWR. I took the box inside and put 50 ohm dummy loads on all ports. Still bad dumped power and input SWR.
Next I started to check the Comtek circuit board carefully. I soon found the problem: in the 90 deg hybrid, the two windings on the toroid were not phased correctly: at one end of the windings, the connections had been interchanged.
I reversed the connections in the hybrid, and now the array seems to function as advertised: F/B is there, minimum dumped power in the few % range, and an upward shift in the array of about 75 KHz over a single vertical.
My experience makes me wonder if they actually test each box before shipping it...
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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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