Backpack-able HF Antennas
As with the radio or rig itself, key issues for a practical HF antenna for a long wilderness backpacking trip should be light, consume little space in your pack and be easy to put into operation. To fit well inside the pack with everything else they need to be physically flexible. My experience with backpacks is that they are stuffed absolutely tight with few "straight areas" for anything rigid or more than a foot or so long. I suppose you could hang some rigid pieces on the outside but the likelihood of damage as the pack gets tossed around on the ground and getting snagged as you clamber through the brush seem like hassles to me. So I lean toward wire antennas. They can be relatively efficient, eminently flexible and fit into a pretty small space.
Throw Lines
2018-08-17 I've tried various combinations of cord and water bottles, etc. to come up with a reasonable throw line for hanging an antenna in a tree. All with varying success. I have learned to use an old re-filled water bottle as very likely it will break in the process. At least once I got the bottle caught in the fork of a tree and could not get it loose. The amazing thing is that it "served" for years through the harsh winters of Wisconsin supporting one end of my G5RV! But I've been fascinated by the yellow line with a little red bag on the end that many use in their YouTube videos! So finally, I broke down and ordered one on Amazon the other day.
|
When it came I was a bit surprised that the bag wasn't attached to the line! So I set about attaching it. My criteria was that the knot should not be snag-able. Of course nothing will ultimately meet that criteria. Trees have an uncanny and unexpected ability to reach out and grab almost anything! But I think I have it, though mind you it is untested at this time.
|
|
I decided to loop the yellow cord through the ring on the little red bag overlapping itself about two inches. Then I used dental floss to wrap and tie the overlapping section tightly together. Finally, I put a section of shrink wrap tubing over that. Whether it works or not, it looks good! I'll let you know down the road whether it is a good idea or just an idea.
Portable Masts
2018-08-07 Another issue with operating portable is how to support your antenna. Trees are probably the most common supports used. And when available and about where you need them, do work well. Sometimes they simply don't work because they aren't available or are in the wrong place, or sometimes are the wrong type for what you want to do. Enter the portable mast. If you are driving to the operating site you can buy or fabricate various masts that can be attached to your vehicle or to a platform of some sort that you can put under a car tire. If you are walking to your site weight and bulk become larger issues and things like fiberglass or bamboo fishing poles may be an option. The ideas are endless. Click here or the Portable Masts heading above for my experiences.
Inverted Vee
An inverted Vee is a good antenna and is about as simple to make as a dipole. It is simpler to set up because it only requires a single support for the center. The ends simple droop down toward the ground so can be tied off to tent stakes, rocks, small trees or whatever. I played with two multi-band versions, a Fan style and a Trap style. The fan style simply has an element (two wires or legs) for each band, in this case 20 and 40 meters. The trap style has a single element divided by a parallel tuned circuit that electrically isolates the shorter portion for the 20 meter band while allowing the full leg length to be used on 40 meters. Each has its advantages and disadvantages. The main advantage of the Fan style is relative simplicity of building and tuning it. It's main disadvantage is that it takes four tie off points rather than two and has more wire to be fiddled with in both set up and take down. The advantage of the trap style is that it only requires two tie off points and so is simpler to deploy. It's main disadvantage is that it is somewhat more complicated to tune.
PAC-12 Rigid vertical |
Dipole |
A dipole is a very good candidate. The down side seems is the requirement of a feed-line and the need for two supports. Of course an inverted Vee configuration makes supporting it easier. A possible negative is that they are generally single band antennas.
A video by K1YPP talks about two portable antennas that caught my eye. The simplest is simply a dipole attached directly to the radio with no feedline or tuner. He suggests it can be configured either like a Vee (as opposed to an inverted Vee) by throwing both wires up into trees. Or you can put one in a tree and the other on the ground. I haven't tried this yet but it sounds interesting. The limitation is that it is a single band antenna.
|
Magnetic Loops |
Another very interesting antenna is the small magnetic loop antenna. Commercially they are kind of expensive. Could one build one that would work? One I saw being discussed by members of the 4SQRP club recently is the Alexloop. I'm not in any way promoting it, it is just one example.
|
End Fed Antennas |
End fed wires are another option. I've played with half wave version in the past but never very seriously. But for this trip I want to explore them more thoroughly as they have the potential of multi-band use which is attractive. A potential negative for almost all end fed wires is the requirement of some kind of tuner or matching network. Two that matching approaches I've had some success with are a simple tuned-secondary transformer with very small primary. I describe it in detail on the page for End Fed Half Wave antennas. The other one is called the Tuna Tunah ii offered by QRPme. Both are built in a tuna tin, so pretty are small and light.
The second antenna suggested by K1YPP in his video is a 51 ft wire and a counterpoise tied directly to a tuner. Another variation I've seen is a 35 ft wire and counterpoise, and I've experimented with using the 33 ft 40 meter half wave on other bands with some success. |
My plan is to explore some of these options, especially the wire antennas as they seem like the best candidates as I see things now.