And Two Other Improved Alternatives To This Basic Design
The G5RV Antenna
Although the popular G5RV antenna is often promoted as an antenna that works well on all bands from 80 through 10 meters, that is absolutely NOT the case.
This is not to say that the G5RV doesn’t work well on SOME bands. But it does NOT work well on ALL HF bands. That’s my point.
There are some bands where the SWR on the coax is out of sight and the feedline losses are astronomical.
The ZS6BKW Antenna
Depending on which bands you want to operate, there is a better design which involves shortening the antenna and lengthening the section of ladder line. G0GSF (ex-ZS6BKW) came up with a similar design that is a significant improvement over the G5RV. Even that design still doesn’t cover all the HF bands
The ZS6BKW’s top section is 93′ (instead of 102′),
and the 400 ohm ladder line matching section is 39.8′, (instead of 30.6′).
Before you buy or build that G5RV, do yourself a favor and Google g5rv ZS6BKW|G0GSF.
- Neither the G5RV nor the ZS6BKW antenna works on 30 or 60 meters.
- The G5RV does NOT work well on 17 or 10 meters. The SWR is a little better on 80 than the ZS6BKW.
- The ZS6BKW does NOT work well on 15 meters, and needs a tuner to work well on 80.
The W0BTU Antenna
Our modification to the G5RV and ZS6BKW antennas, while also somewhat of a compromise of frequency ranges and VSWR, lets us use all HF bands between 80 and 10 except 30 and 60* meters.
EZNEC file for the W0BTU version, which uses a 97′ straight top section, a 39.5′ (or 31′; see below) length of “450 ohm” (usually, the actual Z is 420 ohms) window line, and 75 ohm coax feedline.
You can tweak the lengths slightly to suit your height, operating preferences, etc. The design height of these SWR plots is 40′ above ground.
- Plot 1: Frequency vs. SWR plot with 39.5′ balanced line, 75 ohms (3.5-29.7 MHz)
- Plot 2: Frequency vs. SWR plot with 31.0′ balanced line, 75 ohms (3.5-29.7 MHz)
- Plot 3: Frequency vs. SWR plot with 31.0′ balanced line, 50 ohms (3.5-29.7 MHz)
- 10 Meters: Intentionally optimized for the upper portion of 10 meters
The above bands can be used without switching the feedline, just like the ZS6BKW antenna. However, removing 8.5′ so that the length of the open wire line is 31′ lets this new design also work well on 75/80 and 15 meters.
The W0BTU antenna covers more bands than either the G5RV or the ZS6BKW
A simple DPDT knife switch (or banana plugs and jacks) near ground level lets us use 75/80 and 15 meters, if desired. Even though the VSWR is relatively high on 75 and 80 meters, lower coax loss on that band at least lets us operate there using just one multiband antenna.
NOTE: The remaining 8.5′ section is not connected in any way on 75, 80, or 15 meters. It must be totally removed from the feedline. If one end of it is left connected, the antenna doesn’t work right.
* Well, it will work on 60 meters, if you use
a 76′ length of the 420 ohm window line; SWR is below 1.5:1.
Note that the SWR values in the above charts are at the antenna. Some commercial G5RV antenna designs rely on the loss in a long coax feedline to bring their claimed SWR down in lieu of—or in addition to—an antenna tuner.
You should use a ferrite-core broadband 1:1 current balun (choke) right at the junction of the window line and coax to keep RF off the outside of the coax shield. We used one of K9YC’s (Jim Brown) designs using about 6 turns of the 75 ohm coax feedline wound through 4 or 5 stacked Fair-Rite 2.4″ diameter #31 ferrite cores. A “ugly” balun made from coax wound on an air core is not recommended, as it does not span near as wide a frequency range (see G3TXQ Chokes).
A much better alternative to any of these three antenna designs is running the open-wire line from the center of a dipole all the way to a balanced antenna tuner, which was recommended by Louis Varney, G5RV himself. That antenna will work on ANY band from 80 through 10 meters. (And that’s what I eventually did with this improved antenna design here at my QTH.)
- www.karinya.net/g3txq/g5rv GREAT resource! See the first and last chart on that page, and the note at the end.
- www.nonstopsystems.com/radio/G5RV-1.pdf See Part 3 at the end!
- Good articles about the G5RV