While I've been getting fairly good results with my sloping folded dipole antenna for listening to Europirates, I wanted something with a bit more directionality.
I've known about Beverage antennas for decades, but never used one. I did some reading online about them, I will say, there is a lot of contradictory information.
In a nutshell, a Beverage antenna is a long wire antenna, terminated at the far end. Some authors say you should slope the wire down to the ground at each end, others say to keep it at a constant height, then use a vertical piece of wire at each end. Half say that the wire should be something lossy like electric fence wire, the others say to use coper wire. You want to install it over a poor ground, except for the authors that say you want a good ground. The value of the terminating resistor is critical, except when it isn't. And everyone has a different opinion over how long it should be. You get the idea, the usual situation with ham radio antennas.
I decided that putting up something would be better than procrastinating while sorting out all the details, so I looked around to see what materials I had. I found some antenna wire, but no pieces long enough for the entire run, so I ended up splicing together 4 pieces of different wire. I had a path in the yard that was a little over 200 ft long in the correct direction. Going further would mean hacking a path through brush and possibly poison ivy, so I decided that would be long enough for now. It's 1.25 wavelengths long for the 48 meter band, which according to much of what I read should be long enough for reasonable directionality. The bearing is 50 degrees, which according to a great circle map is what I want to hit Europe (or more precisely get hit by radio waves from Europe).
I bought a pair of 8 ft ground rods and clamps for each end of the antenna. I was dreading pounding them into the ground. Some online reading brought up an interesting suggestion. Fill a soda bottle with water. Push the ground rod into the ground. Then drizzle water down the rod so it goes into the ground. Push the rod some more. Lather, rinse, repeat. Guess what? It works! I was able to get each rod most of the way into the ground this way. I eventually hit some rocks, making hammering necessary, but it was much easier than I thought it would be.
I decided to keep the Beverage roughly uniform in height the entire length, then drop a wire vertically at each end. The antenna runs in a section of the yard with some trees, so I support it with rope attached to branches every so often. It is not completely level, but hopefully close enough.
The far end of the Beverage has a termination resistor. Supposedly the ideal method is to use a SWR meter, transmit at low power, and vary the termination resistance until you have a uniformly high (flat) SWR over all bands of interest. I decided to just go with a value of about 450 ohms, since I had some resistors to get to that value. From what I read, you do want to use power resistors (non inductive of course) since nearby lightning can induce current in the wire, burning out smaller resistors. I cobbled together some resistors in parallel to get to about 450 ohms.
Since the impedance of the Beverage is high (about 450 ohms) you want a matching transformer. I have quite a few cores in the junkbox, but of course no idea what composition any of them are. There's apparently an international law prohibiting marking ferrite and iron cores with a part number. I selected what I thought was an appropriate core, wound a transformer, and connected it to the antenna and some RG-6 coax (I use RG-6 now for all my antenna runs, because it is easy to find and inexpensive). While I got signals from the antenna, the performance was not really that good. Suspecting the problem was the transformer, I looked around some more, and found a balun, either 4:1 or 9:1. (While it was marked, the number had long since worn off) I substituted that for the matching transformer, and voila! success.
In the afternoon, I was picking up audio from CBC on 6160 kHz. There was nothing at all on the sky loop, and occasionally a carrier would pop up with the dipole, but that was about it. I did notice a lot of RFI pickup, then realized that because I was using the antenna with the SDR-14 (powered with an AC adapter) plugged into a laptop, the coax shield was not grounded. I grounded it in the shack, and the RFI went away. Further comparisons later in the evening, once some Europirates were coming in, showed better reception with the Beverage. The overall signal levels are lower, as expected, but the noise levels are much lower.
There's two potential things I can still do. First (and easiest) is the matching transformer, to see if something else will work better than the balun. Second (and much more work) is to hack a path through the brush to extend the Beverage out to about 2 wavelengths or more (which also would improve reception on lower frequencies). But even without either of those changes, I think I have an improved antenna for Europirate reception. And just in time for the Fall/Winter DX season.
