Another antenna plan, this time on a bit of a budget.
After doing so much reading on the Rybakov antenna, I thought it was time to give a go for the lower bands. There are many options for 80 and 40 meter antennas, but a loaded vertical seems to be what I'll be going for. Two custom made coils and a collapsible 18.5' antenna is all you'll need for this project. The result? An antenna that would most definitely be suitable for DX. If Chameleon antennas can make it, then so can you.
The Radiator
I've always wondered why in the world anyone would use an antenna like this:
However, as I got to learning more and more about this style of antenna, it hit me - this is no more than a 1/4 wave at max on 14MHz. The BD7IBI antenna is its name, and 1/4-waving is its game.
I've seen many of these antennas on Amazon, eBay, etc., but never knew why anyone would buy them. After more research, I found out why. This very antenna can tune anywhere from 20 to 6 meters just by adjusting the radiator height. And of course, adding on more radials for efficiency.
The radiator is no more than 18.5 feet fully extended and collapses to just around 2 feet for easy storage. I'm picking one up from AliExpress just to see if this is as good as they say it is. I'm imagining a flimsy telescopic antenna like what you'd find on a standard AM/FM radio - only time will tell.
80/40 Impossibility
You would THINK that 80 and 40 meters would be out of reach for this antenna. After all, 17 feet is WAAAY too short for 40 meter work, let alone 80 meters! But what if I told you that's backward thinking?
You see, in order for any short antenna to radiate on a band that's beyond it's capabilities, we need to lengthen it. We can't physically lengthen it as we only top out at 18.5 feet. But we can ELECTRICALLY lengthen it. In order to do so, we need to add an inductor coil. You can add this to the antenna's base or center, but we're going to base load it since that's easier. Yes, there will be loss. Yes, there will be inefficiencies. But doesn't each and every antenna that has a transformer have this problem?
The idea of base loading is nowhere near new, and Simon (VA7BIX) over at HamJazz on YouTube has bolstered my efforts to create a 40 and 80 meter coil. Initially Simon made a 40 meter coil he dubbed the "Mag7" but he revised it to include 80 meters as well. At one point in his 80/40 video, he wound the coil trying to get it resonant near 3.975 I believe but ended up winding it resonant on 60 meters. So in total, I'll aim to make 2 coils (80/40 and 60) or 3 separate ones (80, 60, and 40).
Michael (KB9VBR) also demonstrated his copy of the Wolf River Coil's Sporty 40 coil and had a MASSIVE pileup on 40 meters during a POTA activation. Not very surprising as Michael is very clear and concise when it comes to building things or activating a park. In fact, I've already signed up for POTA from the influence of Michael and I can't wait to see when and where I'll make my first contact.
Anyways back to the coil...
When we electrically lengthen an antenna, we usually look at making an inductance to cancel out the capacitive reactance of the shortened antenna, or adding a capacitance hat to cancel out the inductive reactance. In addition, this also can give more "length" to the radiator element which will help in the long run.
You have 2 choices when it comes to collapsible antennas - 17 feet and 25 feet. Chameleon makes superb whips in these lengths (SS17 and SS25, respectively), but I've bought one from AliExpress plus an SO239 stud mount and M10 to 3/8" adapter.
Screening for the Ground
Who would've thought that window screen makes an awesome counterpoise?
Michael has done lots of experimentation using aluminum screening you can pick up from your home improvement store. I can get some decent stuff for less than $20 per roll of screen. Remember, with ground planes, the more area the merrier.
If you're feeling REALLY science-y, you can also purchase EMF fabric from suppliers like Amazon. It works the same exact way, and you can customize it to your heart's content. Just beware that this is more thinner than window screening and may not be as durable in the long run.
I think I'll stick with the window screen as I want to see just how budgeted I can make this antenna. For length, get as much surface area as you can on the ground. Even a single 48" x 84" plane will work wonders!
The Lazy L
In recent days, I've come across another brilliant conception by Chameleon antennas. There is a separate kit you can purchase for the SS17 or SS25 that will let your vertical tune up on 80 and 40 without the use of a coil! It's only 60 feet of wire, clipped on the very top via an alligator clip, and it gently slopes down to the ground. I've also heard it called the lazy V too. It looks something like this:
Thank you DJ0IP for the visuals.
As you can see, DX antennas don't have to take up miles of real estate. Yes, while these are compromises, you can still manage decent DX if you take the time to set up your antenna correctly.
I'll come back once I get this antenna put up. It should only take me about 5 minutes to set up and tear down. A much better number in comparison to the EFRW.
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