AA8IA Amateur Radio

Alpha Delta DX-LB Plus – Part 1 : Arrival

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Some preliminary babble…

I had mentioned elsewhere on the site that I’d like to have a 160m antenna. I had given consideration to an inverted-L or a Marconi T, but I came to the conclusion that not only would I not be able to create a vertical section of reasonable height but I also would have difficulty extending the horizontal portion as far as it needs to be and have a proper anchor point for it. And if I could manage to secure the horizontal end, it would be facing a direction that I don’t particularly care about. [It is my understanding that there is some bit of directivity towards the direction that the horizontal portion runs from the vertical portion]

I’d lie if I said I wasn’t interested in 160m DX or working working all states on 160m, but now is not the time to do that. I do, however, want to be able to make my presence known on 160m during the ARRL 160m contest and some of the QSO parties that have 160m as an operational band.

Since I have experience with the 42′ Alpha Delta DX-EE dipole, and since I think it is well constructed and has performed quite well for me, I figured I’d throw down the nearly $200 for the DX-LB Plus dipole. This is shortened 160m/80m (shortened) that will also handle 40/15m, with additional parallel wires for 20m and 10m operation. My DX-EE tunes 30/17/12 and I’m hoping I’ll be able to get a match on these same bands with the DX-LB Plus without too much loss.

The dipole arrived and is still packed up. When I removed it from the box I was surprised at how heavy it was. It’s well constructed. The wire is heavy and of course the addition of the inductors makes it even heavier. I suspect that if I don’t manage to get the dipole erected in a way that the two ends are 180 degrees from one another, it’ll probably cause the top section of my Max Gain Systems mast to bow.

I really can’t stand wiring up the parallel wires. And I really don’t want to think about tuning and pruning it so that it’s resonant inside of the CW sweet spots of 160m and 80m, especially since the 3:1 bandwidth is very narrow.

I’m still debating whether I should put this up as a flattop oriented E/W (broadside N/S) or as an inverted V. Either way the center will be @40 feet. If it is an almost flattop, the ends will be at about 30′. If it is an inverted V, it’ll really be rough to have the ends very far off the ground — probably no more than 10 feet, although I’ll strive for 13-14 feet.

As constructed and delivered, it is intended to be fed with coax. However, I do have the option of feeding it with 450-ohm ladderline (~45 feet) into a DX Engineering 1:1 current balun, through an 8′ piece of RG-213 into the radio. If I have too much trouble tuning the antenna, I may opt for feeding it with ladderline as it will make it easier to tune. Of course, feeding it with a random length of ladderline into a balun is not quite the same as feeding it with only ladderline and tuning it with a tuner that accepts balance feedline.

Already I’m losing ambition, just like I did with the DX-EE. It took me three weeks before I ended up putting the DX-EE together since I had to string the additional parallel wires through their standoffs and secure htem at appropriate points. In this case it’s going to be even more difficult since I’ll be dealing with trying to get it to be resonant in a specific small portion of 160m and 80m.

I’ll write more as things progress

Written by Mike

October 14th, 2010 at 3:52 pm

Posted in Antennas

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2 Responses to 'Alpha Delta DX-LB Plus – Part 1 : Arrival'

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  1. Thanks for your post. I have been considering this antenna, for the same reason (160M contest) but I won’t have time to “build” anything or tune/prune – I guess I thought this just popped out of the box & into the tree limbs in the backyard! Whew – I think you saved me $200!

    Any updates?

    73,

    GJ

  2. Gerry,

    I replaced my ladderline-fed doublet with the DX-LB Plus this spring. I made no attempt to “tune” it for any band, and you can tell. I need to use a tuner nearly everywhere, although 40m was good enough out of the box that I can get by without a tuner on that band.

    It seems to me that on 80m this doesn’t perform as well as the 110+ ft doublet I was using prior. Then again, it could be that I just haven’t used it enough to make a clear statement on that. There has been so much activity on the other bands that I have nearly forsaken 80m so far this summer. Last year 80m was the best band for me with the doublet in stateside contests / QSO parties. This year the sunspot activity has caused a lot of the activity to move up to the higher bands, and so I just wasn’t as much activity in the contests on 80m . So the antenna was probably doing fine on 80m.

    On 40m it works better than the doublet did. It has to be because it has a different pattern. I really enjoy working 40m.

    An internal radio tuner will tune anywhere on 40/20/15/10. Need external wide-range tuner to tune all around 80m. WB2WIK says he uses one on 160m and can tune anywhere he wants with a wide-range tuner — his antenna is higher off the ground and away from obstacles. I can tune anywhere on 80m with a wide range tuner. On 160m, I have only managed to tune one sweet spot at about 1812. As you can guess, the bandwidth is extremely narrow on 160m.

    I’m sure that in the favored directions (broadside) it works better on 40-10m than the doublet would, simply because it would have a more predictable pattern.

    To be honest, the antenna is just too close to the house and too close to the ground for me to give you a worthy review of it. Apex @37 feet, ends at about 4′ off the ground. And the antenna is parallel to the back of the house and about 12′ away from the house. This is far from optimum for this antenna.

    I am confident it would be a completely different beast if it were at least another 20 feet away from the house, if the ends were at least another 10 feet off the ground, and certainly would be better at snagging DX if it were a flattop and/or if it were up around 66′ in the air. Then it’d have gain broadside to the antenna on 40-10m.

    On 80m and 160m it’s shortened, so it’ll never perform like a full length dipole on those bands, and on those bands it’d really require that it were even higher than 66′ feet if you wanted to try any DX with it.

    It is what it is. It’s no miracle antenna. It’s heavy with all of the coils. I’m quite certain if you could get the whole antenna up in the air at a decent height it would work pretty well as far as dipoles go.

    If you can get this antenna [or some other antenna] up higher, in the clear, away from the ground and away from a house, I’m sure it woudl do better on 160m. It hears pretty nicely stateside on 160m — better than the 110′ doublet did.

    There are guys who have an LB-Plus up and say it works great for more localized 160m statesidde activity, and they don’t have a problem tuning it. The difference is that they have the antenna up 20-30 feet higher in the air than I do or at least have the ends significantly higher off the ground than I do. I can’t remember the exact height figure, but I think the ends really need to be up off the ground at least 16′ for it to work well and tune easier. And it needs to be away from large obstructions [like a house].

    $200 bucks is a lot of money. One thing I can say for certain is that the AD dipoles don’t fall apart. They are made extremely well and can withstand some real torture. I’ve had a DX-EE up for a couple years with the weight of LMR-400 pulling straight down on the center of it and nothing has ever broken and the DX-EE as it should for a dipole. The wire used in the AD dipoles is much easier to wrok with too.

    Mike

    Mike - AA8IA

    24 Nov 11 at 9:04 PM

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