Revolutionary 160m antenna at N1TA

I remember it vividly. I was standing on the edge of my toilet hanging a contest plaque, the porcelain was wet, I slipped, hit my head on the sink, and when I came to I had a revelation. A vision…a picture in my head. A picture of this! This is what makes 160m possible from a city lot: the DX capacitor! It’s taken me nearly twenty years and my entire fortune (EDITOR: $300) to realize the vision of that day. Gosh, how has it been that long?

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Basic design of the DX capacitor

The capacitor is easily constructed and inserted at the feedpoint of your series-fed vertical. The smaller the vertical, the better it will work. I constructed my prototype for less than $50 with parts I had in my junk drawer and I’ve already worked 160 Meter DXCC…twice. In a single month. No listening antenna required.

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The prototype in use

Fair warning: the 1.21 gigawatt power supply was very, very difficult; I recommend consulting an experienced local ham and/or astrophysicist (what difference is there?) to help you with the construction. World events and global politics may severely impact your ability to complete this element of the project, so be sure to check ahead of time.

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These angry OM’s chased us home from AES!

I’ve been attempting to bring these to market, but there seems to be little interest from DX Engineering and MFJ. Luckily, Dr. E. Brown Enterprises, located in the new Twin Pines Mall next to the Hill Valley HRO, has agreed to construct and market the device to the amateur market. Please contact them directly with sales and design questions.

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Dr. Brown works out of a van

The next topband season is just around the corner, so don’t wait. Get started on your own DX capacitor today and work the world before you’re outatime!

73
Mike

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Lower 15m beam slipped

It’s been windy here the past few days and the lower 15m beam seems to have slipped a bit when I checked antennas this afternoon. Luckily, it’s restricted by the tower face and can’t go too far so the feedline appears to be alright.

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Low 4L15 spun by the wind

Why does this sort of thing happen? Because the tower leg is too thin for the existing U-bolts on the boom-to-mast plate. I should have drilled the plate for smaller U-bolts before raising the antenna and fixing it to the tower, but it was a few days before CQWW and I had run out of time. There’s little sense in repairing at this point, as this antenna will be taken down with the rest in anticipation of moving to a suitable QTH. I will probably climb up and use rope to secure it, simply to prevent pinwheeling.

This antenna (and the one up top) are homemade 15m monobanders using parts from Cushcraft 4L10’s. I needed minor extension in the elements (only a few inches each) and I extended the boom. I’ll post full details later, in case anyone else wants to try this conversion. They sit on a telescoping tower that is controllable from the shack so we can adjust spacing using a ground-mounted winch. This has been an interesting platform for experiments in stack design; at some point I’ll compile what we’ve learned.

73,
Mike

What does a plasma TV sound like?

I’m a member of a few internet forums where the dreaded “what noise is this?” -question gets asked and I almost always link to this video. It’s one I took a few years ago of the plasma TV in my own home. It also served as a decent close-in test of my (new at the time) switchable beverage-on-ground. One direction is the beverage towards the house (EU) and the other direction is the beverage away (SW).

What kind of ham buys a plasma TV for his own home? Well, it looked the best out of all the TV’s in the store. I’ve heard real horror stories, and this video does most of them justice. I also heard, however, that the noise wouldn’t go away even when the TV was off. This is false; at least in my case, I’d turn it off during contest weekends and have no problem. Hopefully this video will help some of you diagnose your own noise source!

73
Mike

Switchable coaxial BOG

(Note: this is a reprint of a blog post I made August 21, 2013 on an older iteration of this site — I will be uploading additional photos to this post as I recover them)

I often tell visitors that my best antenna is actually my simplest: a 400 -foot beverage-on-ground (BOG) for listening on 160 and 80. It is constructed from leftover RG-213 that I no longer trusted under power. The only expense were the cores, and at $0.40/pc, it was hardly an expense.

I got this design from Low Band DX’ing by ON4UN, with a few modifications. His version was designed around a 50Ω element with 75Ω feedline. My design used a 50Ω element with 50Ω feedline, so I required an isolation transformer. Additionally, I used a series of radials at the far end (for the reflection transformer), but mostly because these radials already existed from a previous project.

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The antenna has two feedlines, one for each direction. The feeds are standard 50Ω coax, and are just long enough to produce a choke. They then go to a relay box so I can switch directions. In the shack, the user interface looks like two sustain toggle switches, allowing the operator to listen NE or SW or both. EDIT: you can see me operating the control to diagnose some plasma TV noise on a later post

So how does it work?

It works well. It is certainly not a real beverage, but it definitely hears better than my 160 and 80 transmit antennas (sloper and linear-loaded tower, respectively). During the ARRL 160 and CQ 160 (ph & cw), I worked many stations that I could not have heard without this antenna. Contrary to popular belief, Europe isn’t so easily had from New England, even when conditions are good, and a listening antenna is often required.

The main benefit of this BOG is that it is a good “family” antenna. If you have a yard that you must share with your kids, dog, barbecue, etc., this is a good solution. When it is time to mow, I simply roll up the coax. Mine stays laid out the full year, but this would also be a great antenna for someone who could only use the yard during the winter. It will work better than your transmit antenna, and if it doesn’t — you just have some spare coax for your next project.

Further experiments

I’ve tried lengthening the element by 50 feet without any noticeable result. I’ve disconnected the ground at the near and far end with only negligible results, and I’ve played with the radials at the reflection transformer (also with negligible results). This is a compromise antenna, but it is somewhat impervious to these changes. It should also be noted that the ground in my area is very, very good.

In the future, I plan to lengthen the antenna even further (I think I can get another 100 feet in during the winter). I would also like to experiment with elevating the element by a few feet to observe any changes.