Here’s one of my favorite antennas for QRP portable operation. It provides easy setup in the field, is extremely compact, and provides excellent performance on all bands 80 thru 15 Meters. It’s a non-resonant antenna, but don’t think for a minute that you lose anything from that. Using a field-radial system as shown, the feedpoint impedances tune readily on all bands 40-15M on my Elecraft K1’s built-in automatic antenna tuner, and I’ve used it with great success with my Norcal BLT Z-match. Gain on all bands is very respectable, except on 30 Meters, where it is nevertheless quite usable. You may want to use a 1:4 impedance transfiormer (toroidal balun) to improve your chances of matching on 20 & 30 Meters, when using the BLT tuner.
Here are the EZNEC-calculated feedpoint impedances for each CW QRP Calling Frequency:
80 Meters (3055 KHz) : Z= 69 +j308 ohms
40 Meters (7040 KHz) : Z= 111 – j232 ohms
30 Meters (10110 KHz) : Z= 1693 + j1466 ohms
20 Meters (14060 KHz) : Z= 239 + j450 ohms
15 Meters (21060 KHz) : Z= 1700 + j591 ohms
I built mine of 87 ft of AWG 22 teflon-coated wire. For a counterpoise, I use four 31 ft radials, formed like an “X”, with two additional 16 ft radials to cover 20 Meters. The radials are AWG 24 wire, also teflon insulated, and connect to a common tie-point, with a 30 inch tail for connecting to the antenna tuner or rig. I prefer the teflon-insulated wire for field antennas, as it tends to be less susceptable to changes due to moisture. While one could use a single counterpoise wire, I believe the extra wire radials help to establish a more consistent and stable “ground” system in the field, and thus more predictable performance from the antenna. Both the antenna and the radial system fit into a sandwich-sized ziplock bag.
This antenna is very flexible in its deployment. You’ll get similiar performance whether it’s deployed as an inverted “L” or a “Sloper”. It will work best with the far end up about 30 ft or more, but it will give excellent performance even if only raised 15-20 ft. In the inverted “L” configuration, try to get the vertical portion up at least 15 ft if possible. Lower antennas will tend to radiate more energy upward on the lower bands, but this is not at all a disadvantage for domestic contacts.
