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write your own review of the Alpha Delta DX-DD.
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WB4TJH
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Rating: 5/5
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Nov 10, 2009 11:17
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perfect now modified
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Time owned: more than 12 months
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This has always been a good, yet limited use antenna. So a couple of years ago, I decided to replace the center coaxial feedline connection with one designed for balanced feed line. NOW this antenna loads and radiates very, very well on all bands, 80-10 meters and with a broadbanded manual tuner, I can tune all bands/frequencies with very low loss. It's a very heavy duty antenna and can withstand a lot of wind and bad weather. Now with the modification of being able to use balanced feedline instead of coax, I have a fine, all band antenna only 82 feet long, that takes care of most of my HF operation. I use 300 ohm windowline from DX Engineering, but 450 ohm balanced line would work just just as well. The advantage of the 300 ohm is its lower wind and icing profile. Winters here in SW Missouri can be pretty harsh and ice storms are common. If you have one of these Alpha Delta antennas and would like to make it even more versatile, consider this modificiation.It turns a dual band antenna into a fine performing ALL bander.
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K4MSG
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Rating: 5/5
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Mar 11, 2009 12:55
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Follow-Up with details
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Time owned: 6 to 12 months
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This follow-up is to report further on the performance of the DX-DD and to offer some insight into its design.
The DX-DD is intended for use where space does not permit a full-size 80-meter dipole (about 134 ft. if cut for the lower band edge). As such, it has the same characteristics as any “shortened” dipole in that it is NOT as efficient as a full-length dipole, due both to its shortened length and to an additional small degradation from loss in the coils installed as part of the antenna. However, at ~60% of full length and with well-designed coils placed where Q is near maximum the DX-DD still makes a reasonably effective 80-meter antenna. In addition, Alpha Delta has chosen a design approach that allows this antenna to work pretty well on both 80 & 40 meters, something a “standard” half-wave 80-meter dipole will NOT do.
Having prior experience with both shortened and “trapped” wire antennas as far back as the early 1960s I decided to reverse-engineer the DX-DD. The design uses the inner section (35 feet each side of center) as a 40-meter dipole with the inductive reactance of the coils causing them to act as RF chokes to isolate the inner section when operating on that band. On 80 meters the coil inductance, which I calculated at about 90 microhenrys, makes the antenna resonant in the 80 meter band despite its too-short length. In a clever twist, the manufacturer has chosen a combination of coil inductance and overall antenna length such that the coil placement location provides both an inner section resonant on 40 meters AND a high overall Q, which is important for efficiency and is a function of where in the antenna the coils are located.
The antenna is well-designed and construction materials are of high quality and should last for years. Coil construction is good and coils losses should be as low as practical. While some feel that the price is too high, it should be remembered that this antenna is intended to be essentially a “plug & play” device, i.e., pay the money, put it up, use it. (If you prefer designing your own antennas and saving a few dollars in the process you shouldn’t even be reading this review in the first place.)
This antenna performs very well on both 80 and 40 meters Minimum VSWR is below 1.5 on 80 meters but the 2:1 VSWR bandwidth is only about 50 kHz. On 40 meters the VSWR is below 1.3 for the first 60 kHz of the band and doesn’t hit 2:1 until about 7175 kHz. It’s obvious that the inner sections are a bit too long and therefore resonant a tad below 7 MHz but I haven’t tinkered with shortening them and having to lengthen the outer sections as a consequence to maintain resonance on 80 meters. I feel that this antenna does what it was designed to do and does it within the expected performance envelope of a shortened dipole, and that’s why I gave it a 5.
One caveat: The DX-DD will load on all bands with an antenna tuner but is a poor substitute for a resonant antenna except perhaps on 30 meters, where it comes close to being electrically 3/2-wave. You can try it on any band and even work some DX with it, but as someone said in a forum recently, “Just because you can load your chain-link fence and work some DX when conditions are right doesn’t make it a good antenna.” So, for anything other than 80 & 40 meters I recommend that you use something else.
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5R8GQ
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Rating: 4/5
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Dec 5, 2008 10:28
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Works Well for what it is
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Time owned: more than 12 months
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First of all, the listed price at the top of this page is wayyy out of date. I just checked online and they currently sell at HRO for $130.95 as of December 2008.
I have had this antenna up for about 8 years. It is installed as an Inverted Vee with the apex at 35 feet and the ends about 9 feet off of the ground. It did not work well at all out of the box. High SWR and difficult to tune. A call to Alpha Delta told me to remove the worthless metal strip they call a "lightening/static protector" at the center connector. Everything was FB after that. Since I use it for RTTY & CW, it worked well at the bottom of the two bands without tuning at all, though the bandwidth on 80m is only about 75 kc (under 3:1 VSWR). Bandwidth on 40m is much wider, but since it is centered at 7.090 I can't fully measure it. Handles a kilowatt RTTY just fine and has stood up well to weather.
I gave this antenna 4 instead of a 5 because of the very high price for what you are getting. come on.....$130 for an 82' wire antenna?
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HFSPOOK
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Rating: 5/5
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Jul 26, 2008 07:09
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Excellent
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Time owned: 0 to 3 months
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The DX-DD replaced a home built 40M dipole. The DX-DD performs as well as the full length unit on 40M and now I have 80M as a bonus. Both bands work great and I get great reports using my home built 40M/80M QRP rig (2 watts).
Robust antenna like the other Alpha Delta antennas I have for ham and SWL.
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KC5NWS
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Rating: 5/5
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Jul 25, 2008 09:55
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very good
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Time owned: 0 to 3 months
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Put up the dx-dd today, one leg is up about 25feet,the other about 15 feet and the center is about 27 feet, runs south and north. Right now using coax and a outboard auto tuner on 75/80.No tuner needed on 40. Results are very good. Getting one leg up at 25ft got me over the ridge to my west and now I can also work 75/80, talked to a station in new mexico at 8;30am on 75 so thats great, talked to the old geezers on 40 this am and my signal is much improved so i am very happy.Later I may go to ladder line and try that.This ant replaces a 40m dipole.
k5jyd in texas
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KY6R
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Rating: 5/5
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May 6, 2008 04:14
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Great Antenna & Service
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Time owned: 0 to 3 months
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I recently converted my Alpha Delta DX-LB to a DX-DD so I could get the antenna up higher - as a 50' flat top. I emailed Don at Alpha Delta and he was most helpful, and I think very kind to support me in my conversion.
I learned a few things as well, and its really great to have an American company, owned by a ham, support their products the way Don does.
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KF2WL
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Rating: 5/5
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Apr 8, 2008 15:07
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Good Antenna
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Time owned: 0 to 3 months
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After having wind destroy my 135 ft inverted vee I put this antenna up in a different location about 35 feet above ground. It works as I was hoping it to work. However I did as previous reviewers did and ran 450 ohm line instead of coax. To a 4:1 balun to rg-8x at 8 foot into the shack.
In this setup it receives better than my end fed half wave. It actually has SWR under 1.5:1 on 15M & 10M before tuning. So after the "mod" I am very happy and the antenna covers all of 75M now.
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IW1QN
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Rating: 5/5
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Jan 9, 2008 10:37
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Works Very Well
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Time owned: 3 to 6 months
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I use the DX-DD Model from 6 Months.
I set up the Dipole like Inverted V and the Highest point is at 7meter of my roof.
I Haven' t another solution and there is not another space on my roof.
The Dipole works very well in DX and I Obtain good results.
I have 1,5:1 SWR on 40m and in 80M the resonance is very little, but I know that the Dipole work better if I can setup the Dipole in better condition.
Form me the Rating is 5/5 because I work without problem good DX in 40 like VK,ZL, and many other.
The Signal from USA are vesry strong.
Good Antenna.
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WB4TJH
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Rating: 4/5
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Apr 25, 2007 09:20
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Works well with mod
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Time owned: more than 12 months
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My full sized 75 meter dipole recently snapped because of some high winds. I had this Alpha Delta antenna in the garage and decided to dig it out. It has always worked pretty well but very narrow banded on 75 meters, so I decided to improve on its frequency capabilities. I removed the coaxial center connector and replaced it with a connector that takes balanced feedline. I connected 300 ohm windowline to the antenna (450 ohm balanced line would also work just fine) from my previous 135 foot dipole. The balanced feedline comes down to a DX Engineering 1:1 balun in a waterproof enclosure on a short post driven into the ground with an 8 foot groundrod beside it. A 6 foot piece of coax goes from the 1:1 balun thru the wall of my house to my MFJ tuner. Now I can enjoy 80 thru 10 meter coverage with this 82 foot long antenna and not have to worry about its narrow coverage on 75 when used with coaxial feedline. I also have an Alpha Delta DX-EE 40-10 meter antenna thatI am thinking about modifying the same way. Balanced feedline is super low loss and SWR worries are non existant with this setup and a good 1:1 balun and an antenna tuner. DX Engineering recommends this setup over using the built in 4:1 balun in a tuner, and I have to agree it is a super antenna system. I have the 82 foot DX-DD in an inverted V configuration with the apex at about 55 feet. It is a super antenna and does very well on 75 with this setup, and swr is no longer a factor with the balanced feedline.
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KC4CP
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Rating: 5/5
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Apr 20, 2006 08:33
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NEW RATING
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Time owned: 3 to 6 months
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You can read my previous review & see that my only complaint was narrow bandwidth on 80 meters & trouble tuning outside of bandwidth of 80. Since last review, I have played around with the positioning of dipole legs & I now give it a 5 rating.
I can now tune anywhere (with a variety of tuners) and get great signal reports ... even on 80 meters. I continue to get great signal reports on 40 (absolutely great). And now, 75/80 meters performs equally as well.
I have a couple of ham friends who live close by and who use full length, mono-band 80 meter dipoles. When we have worked the same station, at the same time, I am never more than 3db less than them ... and at times, I get a slightly better signal report.
I now consider this to be a "compromise" antenna ... only in the fact that the length is compromised (82 feet total length). Other than that, performance is superb!
ADDED COMMENT: Antenna is installed as an inverted V ... with apex at 38 feet ... & legs 15 feet off the ground.
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