Cheap and EZ to build Bi-Directional VHF & HF antennas with gain
Image from Original CQ Magazine article
Skeleton Slot Antenna this antenna is very similar, if not the same antenna
Thanks for all the interest in these antennas, please tell me about your success stories, at below address.
In the September 1995 issue of CQ Magazine, Paul Carr, N4PC, published and article about a new 17 Meter antenna he had designed, called "The H Double-Bay".
In September 1995, a 4 element 40 meter KLM log-periodic-yagi was being used by AA4S as a 17 meter antenna for casual DXing with reasonable success.This was being done primarily because Roger Burt (N4ZC) had indicated his 40 meter KLM tuned and worked well on that band.
A linear-loaded rotatable dipole and delta loops in various configurations had all been tried with only mediocre results.AA4S was late getting on the WARC bands and by 1996 had logged only 62 entities on 17 meters.
In April of 1996 an H Double-Bay was constructed from Paul's article.It was hung off the side of a 75-foot tall tower with the top spreader at 72 feet.A fiberglass rod secured to the top of the tower supported the antenna about 8 feet out.Ropes were attached to the ends of the bottom spreader and run to a tee bar arrangement fixed about 5 feet above ground in order to allow manual rotation when necessary.
Results using it weren’t particularly exciting until a direct comparison with the 40 meter KLM was made on May 19 with ZL2BPT.Graham indicated the "H-Bay" was as much as 2 S units stronger than the KLM!As a result, it has been used ever since on 17 meters with 299 entities having been logged to date.
The performance of this antenna on 17 meters led to the construction of similar ones for 10, 15, and 20 meters for use in HF contests.They are hung from a rope strung between two towers fixed broadside southeast/ northwest (~145 / 325 degrees from AA4S) for the purpose of making QSOs and working needed multipliers in their favored directions (primarily, the Caribbean and South America) whileyagi’s are pointed elsewhere.Results have been considerably better than expected using this strategy.
Using signals from the international beacon system for comparison, the yagis came out 4 to 5 dB better than the Double-Bays.This wasn’t too disappointing, however, in that antenna requirements for the intended purpose are not that demanding and because the mono-banders in use for 20 through 10 meters at AA4S are generally much higher.They consist of a 5 el 205CA at 87 feet, a 4 el W2PV redesign of a 155BA at 60 feet, and a 5 el N6ND redesign of a 105BA at 62 feet on 3 separate towers.These modified Hy-Gain® antennas have served quite well under even the most difficult operating conditions.
The greatest advantages of H Double-Bay antennas are that they can be constructed and hung for very little in terms of both time and money compared with mounting beams for various directions either on side-arms or on additional towers. At more modest stations these wire antennas will likely outperform other types of antennas especially in cases where erecting a tower is not practical.Tree limbs can often provide adequate supports.
Modeling software (EZNEC 3.0) was purchased in an effort to learn more about these antennas.Why did they work so well?One of the first things discovered was that their 3 dB beam width was 88 degrees.This meant that two of these bi-directional antennas at right angles to each other would basically cover all directions.
A second observation was that if the height of the middle spreader is placed at the same height as a yagi for a given frequency, the major lobe of the H Double-Bay has the same elevation angle as the yagi – but in two directions.Free space gain figures compared to a dipole were found to be roughly 4 dB.These observations were relayed to several Carolina DX Association (www.cdxa.org) members.Eventually articles were written about them which were published in the “Pileup”, the CDXA’s monthly club newsletter (Jan & Feb 2003) (see links on left)
There has been a need for good inexpensive antennas for SSB and CW use on the VHF bands. This has especially become an issue with all of the Icom IC-706, Yaesu FT857, HF-VHF-UHF all in one rigs currently on the market. The H Doublebay has proven itself to be a great performer on the HF & VHF bands. Heres how it was adapted for VHF applications...
Bill W4GRW asked, “Why couldn’t this type of antenna be used on six meters?” The question wasn’t taken too seriously until it became obvious why he was asking.We are part of a team which has operated in the limited multi-op category at AA4ZZ for the past several years.We had always used large arrays of long-boomed yagis either stacked or as four bay arrays with power dividers.
Unfortunately, after almost every contest we received complaints that people had called us all weekend, but we never heard them.It became clear that we were missing a lot of contacts because the beam width of our antennas was too sharp.We needed more diversity. Shortly thereafter we began using H Double-Bay antennas on six meters. Initially, one was hung facing broadside northeast / southwest.We were so pleased with its performance, that two double bays (SE/NW and E/W) and one “four bay” (NE/SW) are now a permanent part of our six meter station to complement the two stacked 8 element yagis.
We are finding that the “Bay” antennas not only provide directional diversity at the flip of a switch, but they also have sufficient gain at the necessary elevation angle to make double-hop E-skip contacts. We have used them successfully during aurora conditions; and, because they are closed-loop antennas, they are not adversely affected by rain static, whereas, the yagis sometimes are.
The basic dimensions of an H Double-Bay antenna designed for 50.125 MHz. are 26.33 inches wide by 87.38 inches timestwo (or 14’ 6-3/4”) high based on using #12 bare copper wire.We have also used #14 insulated* wire which shortens the bay heights to about 85 inches.Small adjustments can be made by moving the bottom spreader up or down.Even the most elaborate model (e.g. using PVC spreaders with end caps and Wireman Part #801 as a center connector) can be made for less than $20!
At this point we aren’t satisfied with just our six meter success.We are experimenting with their use on bands as high as 432 MHz.AA4S hasworked “Skip” (KH6TY) in Charleston, SC from his QTH in Shelby, NC (191 Miles) using 100 watts to a 2 meter double-bay at 60 feet fed only with RG11.W4WA in Lula, GA (128 Miles) was worked on 432 MHz. using 35 watts and a four-bay design during this January’s ARRL VHF Sweepstakes.
What if we want more gain? The term “four bay” has been used above and deserves explanation.The technique of stacking bays vertically instead of placing 2 Double-Bays side-by-side to achieve more gain, for example, has the advantage of keeping the same 88 degree 3 dB beamwidth rather than reducing it to ~44 degrees.Neither is a power divider required.
W4GRW and his son Josh (W4WJF) recently used 2 each four-bay 144 MHz. antennas placed at right angles to each other from our Boone, NC contest location during the CQ VHF contest with excellent results.
So what is the purpose of discussing these antennas? Hopefully, by introducing newcomers in the hobby to inexpensive but effective antennas which can be easily constructed and installed, we can get more people to use the VHF/UHF bands. Think of how many Icom IC-706 type rigs are sold, that have never been on the VHF bands because of antenna considerations. This will not only help the more serious among us to achieve our VUCC goals but also may, by coincidence, create additional contesters who will increase our scores by working us.
There have been several recent contesting efforts using H Doublebay antennas, with outstanding results.
Josh Fisher, W4WJF, First Place, 2005, 2006, 2007 CQ WW VHF 2M SOSB
Bill Fisher, W4GRW, Third Place, 2006, 2M Fall Sprint
Bill Fisher, W4GRW, Certificate, 2006 CQ WW VHF 6M SOSB
AA4ZZ Contest Team, Fourth Place 2006 ARRL Sept VHF QSO Party
AA4ZZ Contest Team, Fifth Place 2006 ARRL June VHF QSO Party
Dixie Radio Pirates, 2007January ARRL January VHF QSO Party