One of my passions is experimenting with antennas, wire antennas for HF to be precise. I want to be able to improvise and adapt to the situation at hand whether I’m at home, traveling on business, or hiking in the desert or deep forest.
Here’s my set of requirements for HF portable antennas:
- Usable on mathematically-related bands: 80M, 40M, 20M and 10M;
- Reasonably snag-proof through tree limbs, etc.;
- Low “parts” count; and
- Able to “mix and match” for any situation.
To those ends, I have fabricated a “kit” of various lengths.
Starting with 200′ of PolyStealth from The RF Connection, I cut the following wire segments:
|Qty @ Length||80M||40M||20M||10M|
|1 @ 66’6″||λ/4||λ/2||λ||2 * λ|
|2 @ 33’3″”||λ/8||λ/4||λ / 2||λ|
|4 @ 16’7.5″||λ/16||λ/8||λ / 4||λ / 2|
These will be used with the “No-Tune” EFHW Tuner by WA5BDU (toward the bottom of the linked page) for which I bought the needed FT-114-43 toroid at Kits and Parts dot Com and assembled it using hook-up wire and an aluminum minibox with appropriate (BNC and banana jack) connectors. All of the latter were obtained at my local Fry’s Electronics store.
After carefully measuring and cutting — “measure twice, cut once” — I added stacking banana plugs to each of the seven wire segments to facilitate their interconnection in various combinations. (If I lose a banana plug or two when pulling the wires down out of a tree, well then so be it.)
For 80M operation, the long (66’6″) segment will be a λ/4 vertical and will be driven directly (without the “No-Tune” EFHW Tuner). For this, a simple BNC to banana plug/jack connector will suffice. Two ground radials will be added by combining the two medium segments (2 * 33’3″) into a λ/4 piece and the four short segments (4 * 16’7.5″) into another λ/4 wire. The finished antenna therefore consists of a λ/4 vertical with two λ/4 radials.
For 40M operation, the long (66’6″) segment is again used, but this time as a λ/2 antenna. Because it is end-fed, its high impedance needs the “No-Tune” EFHW Tuner. The two 33’3″ segments are then used individually as λ/4 radials and the four 16’7.5″ segments are combined, two at a time, into two more λ/4 radials. The result is an end-fed half-wave vertical (or more likely an inverted “L” depending on available trees and other supports) with four λ/4 radials.
For 20M, the long (66’6″) segment could be used as a full-wave (λ) radiator (with the EFHW transformer, of course). But another possibility would be to fold that wire over onto itself and plug the two ends into each other (using the stackable banana plugs) and, thence, into the antenna connector from the rig creating a shorter λ/2 radiator. I have not seen this configuration described elsewhere but, as long as the two halves of the folded-over wires are close to each other, I think they may act the same as one wire since they are both fed with the same signal. (Some experimentation is needed to confirm this.)
The four short (16’7.5″) segments are then used as ground radials. (The 33’3″ segments are not used.)
Use on 10M takes one of the short (16’7.5″) segments into a λ/2 antenna (connected to the EFHW transformer), and the remaining three can be folded over, plugged in to themselves and used as three double-wire λ/4 ground radials.
(Oops! I should reverse
the BNC and Antenna
connectors to match
Finally, for a 40/20/10M combination all in one assembly, I’ll use the long segment as the vertical or inverted “L”. The remaining wires are connected as ground radials of various lengths but always with at least two pieces being λ/4 long on each of the three bands. (Two of the shortest pieces are folded over and connected to themselves for the λ/4 radials on 10M). The entire assembly is then fed via the EFHW Tuner.
That assembly will also work on 80M with the removal of the EFHW Tuner where the 66’6″ long segment is a λ/4 in length and, therefore, a low impedance at the feed point.
Today, I’ll put up one of the 20M configurations here at the home QTH. I’ll run a short piece of RG-8X from the rig out the shack’s window to the “No-Tune” EFHW Tuner, and string the antenna up the side of the house and lay it on the roof in an inverted “L” configuration. The radials also connect to that box and snake out over a 180 degree arc.
Time permitting and with a second short trip to the roof, a 40M configuration can be tried as well.
Note that no tuning of wire lengths can be done; the “mix and match” nature of this kit precludes it, or at a minimum makes it difficult to do.
But in this regard, an antenna analyzer will, someday, be put to good use. With that, the above assembly could be quickly measured for resonance on each of the four bands and wires trimmed — but reasoning out the sequence of measure and trim operations across the four bands such that no wire is ever cut too short … well, that thinking will be left to a future time. (But I’ve started collecting parts for the analyzer which will be the subject of a later article.)
In the next few days and if all goes well with my initial trials of the different configurations, then I’ll order a 31′ sectioned fiberglass pole from JackTite along with the ground mount (stake) for portable operation (where the ground is soft enough for the stake — that’s not in the Phoenix desert, by the way), and also the Wall Mount to be attached to the home QTH so I can use it as a free-standing “instant” vertical that is put up for operation and then taken back down to minimize notice by the neighbors.
Using the above ground stake, the 31′ pole is a tad short of the needed 33’3″ for the 40M quarter wave (20M half wave, 10M full wave) so I’ll need to either let the last two feet of the wire antenna just flop over, or strap the pole to a tree a couple of feet off the ground or something similar. (A set of variously sized bungee cords will be used to secure the antenna to the pole, and the pole to a tree.)
Down here in the desert, however, trees are in short supply and, in some areas, the sentinel-like Saguaro cactuses are not always present. So in some areas, the based of the antenna mast will be secured with rocks and a couple of guying strings will be needed near the top of the mast to hold it straight up.
So, here’s the final parts list for the HF Portable Wire Antenna Kit:
- Seven wire segments, cut to the lengths described above, and with stacking banana plugs installed;
- WA5BDU’s “No Tune” EFHW Tuner;
- RG-8X coax with BNC connectors (length not yet determined);
- BNC to banana plug/jack adapter (80M only);
- Plastic baggies for wire segments, tuner and adapter;
- Jacktite 31′ telescoping fiberglass pole;
- Ground mount stake (for Jacktite pole);
- 200′ string for guying the Jacktite pole; and
- Misc. bungee cords.
Each location where I use these wires will be unique. Having a good set of “mix and match” components from which to assemble a workable antenna is essential.
That ability to improvise to the needs at hand is, after all, one of my goals.