One of the biggest problems for HF op­er­a­tors is the lack of a good wide band an­ten­na for 80 Me­ters. I re­cent­ly ac­quired a Yae­su FT-950, which has a built in trans­match which will han­dle 3:1 SWR. Fur­ther, my John­son Valiant does not load di­rect­ly in­to a stan­dard dipole with­out a trans­match all the way across 80 me­ters. I got enough knobs to twid­dle with­out ad­d­ing a trans­match when go­ing from CW to phone. It now works all the way with­out touch­ing the coarse cou­pling at all from 3.6 to 3.9. It nev­er re­sults in a tun­ing so­lu­tion that can­not be matched by the plate tun­ing or em­ploys wide open cou­pling sett­ings above 3. This in­di­cates a well be­haved low re­ac­tance load. Dit­to for the Vik­ing 2.

Al­so, since I can­not af­ford a tow­er, a good an­ten­na has to hang from ex­ist­ing trees and can be launched with a com­pound bow with some sur­vey­or's twine to pull up the sup­port­ing rope. I have put up field day an­ten­nas at 100 Feet us­ing this method be­fore. My trees have side branch­es, and I like to use a pul­ley to tune and ser­vice the an­ten­na. So I had to set­tle for about 35 feet height, which is good for lo­cal work on 80 me­ters. I do have a high per­for­mance ver­ti­cal for long haul stuff, but on­ly en­gage it when talk­ing out­side the low­er 48 states.

This ar­ti­cle is meant to ad­dress this is­sue with a de­sign that is me­chan­i­cal­ly sen­si­ble. I will first dis­cuss some of the al­ter­na­tives that have been of­fered over the years and lay out their flaws, and why this idea is bet­ter. My firm­ly held opinion is that if you have more than 3:1 SWR on your an­ten­na, you need a new an­ten­na. Al­so, us­ing loss to ob­tain band­width is on­ly a last re­sort. The typ­i­cal G5RV is fed thru a balun (loss) and of­ten 100 Ft of coax (of­ten RG-58/U more loss) for field day, and peo­ple brag about how well that loads. Prop­er­ly op­er­at­ed with no coax and a true bal­anced tun­er like the John­son Match­box, it will per­form OK. But if that's your style, this ap­proach is not for you.

STAN­DARD DIPOLES, CEN­TER FED ZEPPS, TUN­ERS AND OTHER HASSLES

While many hams like open wire feed line to a flat top, there are rea­sons not to do it this way. First, I hate hav­ing to ad­just half a dozen knobs to QSY and stress the fi­nals with off re­s­o­nance load­ing op­er­a­tions. Then there is loss in the trans­match, one or two dB. If you run coax to get through the wall of the house, add a balun, then go to open wire, add another one or two dB. Ad­di­tio­n­al­ly the open wire line gets lossy and un­pre­dictable when it is wet; coax does not. If the line is "hot" your com­put­er goes nuts or there is RF on the mike caus­ing dis­tor­tion or other problems. Us­ing coax to a stan­dard 80 me­ter dipole with a 1:1 balun at full pow­er and force feed­ing it at the CW end when the dipole is cut for phone will set fire to a W2AU balun in a hur­ry. A balun may work rea­son­ab­ly well in­to a re­sis­tive load, but ad­d­ing it to a 80 me­ter stan­dard dipole will sure­ly abuse it, and al­so add loss in the form of heat in­stead of ra­di­at­ed RF. Get rid of the balun and you will do OK with a stan­dard dipole on your fa­vorite fre­quen­cies. Let the coax ra­di­ate if it choos­es, or add a choke balun made of a coil of coax; at least you are gett­ing RF in­stead of heat. But I like all modes, and I do not like slow QSY. Keep this in mind for field day when some­one is putt­ing a brick on the key for YOUR RIG to load in­to a G5RV and melts the fi­nals. If you can on­ly put up one an­ten­na, I dis­cuss the multiband Jet­stream dipole ap­proach. This ar­ti­cle takes that con­cept to the next lev­el, and com­pares the im­prove­ment in band­width.

BA­ZOO­KA

The ba­zoo­ka an­ten­na is made from coax el­e­ments in the ra­di­at­ing por­tion of the dipole. First, it is me­chan­i­cal­ly un­de­sir­able due to the weight. Wind and sup­port is­sues elim­i­nate it im­me­di­ate­ly, and that is not the on­ly flaw. Walt Maxwell thor­ough­ly de­bunks this de­sign. He shows that the loss­es in the coax pie­ces are the rea­son for the low SWR.

T2FD

The T2FD fold­ed dipole sim­i­lar­ly us­es loss­es, this time in a re­sis­tor to ob­tain low SWR across the en­tire short­wave spec­trum. Fur­ther, it em­ploys a 12:1 VOL­T­AGE Balun. Vol­t­age baluns are in­her­ent­ly in­ef­fi­cient, par­tic­u­lar­ly in­to in­duc­tive loads. We can do bet­ter in near­ly the same space, with less vi­su­al im­pact. The wife and home­own­er's as­so­ci­a­tion will ap­pre­ci­ate this ap­proach bet­ter.

FULL WAVE HOR­I­ZON­TAL LOOP

The full wave hor­i­zon­tal loop WILL give bet­ter band width than a dipole. At heights be­low 20 feet, it will out­per­form the dipole on lo­cal con­tacts, since it is a cloud burn­er. The dipole will have more ground loss than the loop. But for gen­er­al pur­pose work at longer dis­tances, it is not a good choice. Fur­ther, if coax fed via a ¼wave of 75 ohm line to match its high­er impe­dance to 50 Ohms, it be­comes a one band af­fair. The fi­nal prod­uct here is du­al band 80 & 40 Me­ters with no com­pro­mise.

CAGE DIPOLES

Cage dipoles work by in­creas­ing the di­am­e­ter of the ra­di­at­ing el­e­ments. Beam an­ten­nas use pipe in­stead of wire to achieve this ef­fect, al­though Yagis can be fab­ri­cat­ed from wire and hung from rope. The larg­er con­duc­tor low­ers Q and in­creas­es band­width. Go­ing from small guage wire to #12 wire re­duces loss due to cop­per re­sis­tance loss­es, but it is not a sig­ni­f­i­cant enough change to add band­width to a dipole. A cage dipole typ­i­cal­ly at­tempts to si­m­u­late a wire di­am­e­ter of 8 feet or so, and it works well. W1AW us­es a cage dipole for 80 me­ters to keep its new solid state high pow­er am­pli­fiers hap­py. How­ev­er, the me­chan­i­cal problems of sup­port­ing such a struc­ture in windy and icy con­di­tions make it a pro­ject.

COLLINS DIPOLE

The so called Collins dipole was made pop­u­lar back in the 50s as an an­sw­er to trans­mit­ters that did not tol­er­ate more than 2:1 SWR. The 32V se­ries was fa­mous for da­m­age to the L net­work fixed ca­pac­i­tors and as­so­ci­at­ed load­ing switch. I changed a lot of them for friends. It is in the shape of a bowtie, and of­ten in­clud­ed a balun. A re­cent ar­ti­cle in Elec­tric Ra­dio mag­azine (Septem­ber 2013) by Chuck Fel­ton, KD0ZS got me to think­ing about this idea. He achieved re­s­o­nance at 3.8 with 1.2:1 SWR and 200 KHz be­tween the 2:1 SWR points. The ends of the "bowtie" in his de­sign are 9.5 feet apart. I won­dered if spread­ing them fur­ther (say 30 feet) would be even bet­ter, and so here we go.......

THE AB2RA BROAD­BAND 80 & 40 ME­TER BOWTIE DIPOLE

Re­fer­ring to Fig­ure 1, the an­ten­na com­pares the de­sign for­mu­las and shapes of vari­ous broad­band an­ten­na de­signs. My for­mu­la comes from em­pir­i­cal work, not fan­cy math. But it should get you in the ball park, if your height is the same. Mine was at 35 Feet or so, and the impe­dance, while re­sis­tive, is low­er than 50 Ohms as ver­i­fied by my MFJ An­ten­na An­a­lyz­er. Your at re­s­o­nance SWR will im­prove with heights of around 50 feet. If you go high­er, the at re­s­o­nance impe­dance will go to 70 or even 90 ohms, ac­cord­ing to usu­al dipole impe­dance charts. Most of the Collins Dipole de­signs join the ends of the bowtie with a jum­per that con­nects points on the wire that are the­o­ret­i­cal­ly at the same po­ten­tial. I spec­u­lat­ed that was un­ne­ces­sary. Look­ing at stan­dard UHF TV an­ten­nas us­ing bowtie de­signs, they achieve wide band per­for­mance with­out any wire on the end; it is just a sim­ple V on ei­ther side. Maybe ad­d­ing a cen­ter wire so that there are three dipoles in­stead of two might help. I did not have con­ve­nient­ly lo­cat­ed trees to ex­plore this idea, and it worked well enough with­out it. I al­so had to fold one leg as shown in Fig­ure 4, the "as built" draw­ing of the ac­tu­al in­s­tal­la­tion. If yours can be laid out straight, it will like­ly work bet­ter than mine. I tried to get all the wires the same length, but this is the way it turned out. Per­haps if you tune a pair to 3.6 MHz and the other to 3.8, you will get even bet­ter re­sults. If the pair is 90 de­grees apart, the tun­ing in­ter­ac­tions might not be as much, and it would al­low om­nidi­rec­tio­n­al cov­er­age. I sus­pect the at re­s­o­nance SWR would be clos­er to 1:1 at 70 to 100 feet. I leave this to the folks with de­sign soft­ware and more room on their lots.

This an­ten­na is easi­er to erect than the T2FD, cage dipole, or Collins Dipole. There are no spread­ers. It is just 4 wires con­nect­ed to a cen­ter in­su­la­tor. A cen­ter sup­port is pre­fer­able to bear the weight of the coax. I use the best cen­ter in­su­la­tor avai­l­able, all stain­less hard­ware, from the Wire­man. I use Coax-Seal or Duct Seal from your lo­cal elec­tri­cal sup­p­ly house to seal all coax con­nec­tors. Al­low enough slack to al­low the trees to sway in the wind. Chuck Fel­ton's de­sign was an in­vert­ed V to al­low at­tach­ment of the 160 Me­ter el­e­ment to be at­tached with­out the use of a lad­der. I have a good 160 Me­ter Loop, and on­ly need­ed 80 and 40 to add to it. So I put the ends as high as I could get them. Typ­i­cal­ly, band­width is bet­ter on a stan­dard dipole com­pared to a V, all other things be­ing equal.

THE PROOF OF THE PUD­D­ING

Re­fer to Fig­ure 3 BOWTIE 80 ME­TER SWR to see the fi­nal re­sult. The MFJ An­ten­na An­a­lyz­er reads sig­ni­f­i­cant­ly high­er than the pan­el me­ter on the FT-950 and the other me­ters I have, so I sus­pect that it is bet­ter than shown. The 950 is hap­py with its in­ter­nal tun­er me­m­oriz­ing vari­ous sett­ings. The Valiant al­so is hap­py. Be­low 3.6, I use 0, 1 or 2 on the Coarse Cou­pling. From 3.6 to 3.9, it likes 3. From 3.9 to 4, it us­es 1 or ze­ro. There are no spots that can­not get a good dip on the plate tun­ing or em­ploy coarse load­ing wide-open which would cause har­mon­ic ra­di­a­tion.

Back in the day, the miltary had really good tech schools. A soldier in the field did not have time or calculators and had to get the job done. Here is a chart from a Field Guide to antennas prepared by Stanford University for Project Agile. It even has a page in it for modding the BC-610. Basic antenna theory has not changed a bit from that time, other than having better computer modeling. If you want to get your station up and running with an effective antenna, use this chart to prune for best SWR, on just one try. Later, I may add nomograph lines for 14, 18, 21, and 28 MHz. Click on the chart to enlarge it. Print it out from there if you find it useful. For now, this chart is same as the original published at:
http://www.dtic.mil/get-tr-doc/pdf?AD=AD0684938.

Or if you would rather use a calculator, Don AC2RS has developed a tool for pruning dipoles in one step. See it at: /Projects/Antennas/AntennaCalc.html.

THE 40 ME­TER ADD-ON

I add­ed a 40 Me­ter el­e­ment. Noth­ing changed on 80 me­ters. In the SWR charts, I com­pared it to the Jet­stream Multiband 80 through 10 me­ter dipole this an­ten­na re­placed. See Fig­ure 2 for the raw da­ta. See Fig­ure 5 for the SWR curves for 40 Me­ters. The 40 Me­ter an­ten­na that was part of the Jet­stream was ad­just­ed for phone op­ti­mum. It did pro­vide op­er­a­tion with a tun­er on 15 Me­ters. The new an­ten­na for 80 & 40 on­ly was set for mid­band on 40, and it de­liv­ered 2.4:1 all across 15 Me­ters, and the Yae­su and Valiant load­ed it with no ex­ter­nal trans­match re­quired. I did not count on this, but it solved the problem of 15 Me­ters nice­ly. I sus­pect the 20 and 10 Me­ter el­e­ments com­pli­cat­ed the 15 me­ter op­er­a­tion. Hey, it works with this length of coax (about 100 Ft to the ra­dio). Your mileage may vary.

Some Measurements:

My article on this was published in Electric Radio (http://www.ermag.com/) issue #308 January 2015.

For a mathematical approach to follow up, see QST February 2015 "The Doctor is In" page 67. That author does a EZNEC analysis of this same concept using stagger tuned dipoles at 90 degree angles which provides a W shaped SWR curve and full 3.5 to 4.0 with less than 2:1 across the entire band. This approach achieves all that a cage dipole promised without the mechanical complexity. He also covers some of the folded dipole and coupled resonator approaches to broadband dipoles which have equal mechanical complexity.

Speaking of math, if you eliminate the antenna tuner and buy some good coax from JefaTech: (link: http://www.jefatech.com/category/d100-ll400, review: http://www.eham.net/reviews/detail/9735) you get the convenience of no knob QSY, no weather worries due to rain and ice, and less mechanical hassle than open wire, at a lower price by eliminating the tuner with equal performance on feedline loss.

5/29/17 UPDATE: BROADBAND DIPOLES STAGGER TUNED TO 2 FREQUENCIES WORK BETTER THAN BROADBAND DIPOLES WITH EQUAL LEGS

An August 1968 QST article by Howard W4RZL, republished in ARRL Wire Antenna Classics First Edition, was in the back of my mind as a possible improvement to the 80 meter broadband dipole I already had installed. It agreed with my findings that the Collins Broadband Dipole (with equal length wires) 12 foot end spacing did not perform as well as might be expected. The W4RZL research showed 20 to 40 feet spacing at the dipole ends and different dipole lengths was significantly better. W4RZL also used a multiband scheme for 40 and 20 along with the 80 meter dipole. Building it with multiple bands makes each band narrower. You can see the curves for 20 and 10 meters comparing the dual band and Jetstream all band dipoles below.

Neither the W4RZL nor the Collins Dipole had the severe mechanical disadvantages of the so called "Cage Dipole". Both were equal to or better than the Cage Dipole in SWR performance.

As part of my routine spring service on all antennas, I took it down and measured it. I was not satisfied with the tuning and measurements I had done in haste with an approaching winter.

This spring, I took the antenna down, and chose the longest dipole and added bare wire of about 15 feet to it, to tune it way below the ham band. This allowed me to characterize the resonant frequency of the shorter dipole. Then I gradually shortened the longer dipole, making it approach the frequency I wanted. Unless the dipoles are perpendicular, the tuning of the two dipoles will interact. If the two dipoles are tuned to 3600 and 3975 as suggested in the W4RZL article, there is a W shaped SWR response that could peak in the center of the band that approaches or exceeds 2:1. I tuned mine to about 3900 and 3650, to lower the mid band SWR peak. I wanted the very best SWR on phone, with improved response on CW over a regular dipole. This in no way demeans the work of Collins or W4RZL; I just wanted a different result. The Antenna Classics also has a dipole with only one wire element, but uses reactive elements to obtain broad band response. I just like the simplicity of this design shown here.

I also used a couple of measuring methods. One was a standard SWR/Power Meter made by Heathkit, the model 2140. I really like this meter, and with care during calibration, the peak reading function even works pretty well. For an inexpensive meter, that is unusual. The second method of SWR was the MFJ 259 Antenna Analyzer. That one was calibrated using the methods detailed on the W8JI website. Both of these correlate pretty well. The MFJ also provided Resistance and Reactance (no sign displayed on my older model). The Zero Reactance points on the SWR graph are very enlightening. These are true resonance points which would be picked up by a grid dip meter. W4RZL uses a Millen GDO in his article. W4RZL also does not use a balun, and tries his design with a variety of feedline lengths; he found that his design was relatively independent of these factors. It is also noteworthy that the reactance does not go above 25 ohms over a 500 KHz band width; over much of the phone band, it does not exceed 15 ohms reactive. Large amounts of reactance is what solid state rigs and amplifiers do not tolerate well. Being able to operate directly into an antenna without the added loss of a tuner is well worth the work. The Dentron MT-2000A specifies 0.5 dB maximum loss at match condition, one of the few who actually publish it. It is one of the best out there, and much more rugged than the Ten Tec 238, which also claims low loss.

I did not include the resistance measurements as they would just add another layer of confusion. It wandered around 35 to 40 ohms, expected at the 45 foot height. Anyway, here is what I got in the real world, measured in the shack where my equipment was located. That is where it really matters to me. I am not going into antenna models (with all their assumptions). What kind of ground you have at your location will influence the final results. What really matters is what your radio sees, not thetas and betas. I do plan to put a ground reflector under this antenna later. I will update this site with more data if that is significantly different from what is shown. A ground reflector theoretically will improve the efficiency, especially at near vertical angles. I am always thinking ahead to the next improvement. But for the time, here is the actual measured SWR of the present antenna. You can clearly see the W shaped SWR curve resulting from two distinct points of resonance, unlike the original data posted here. Also the new SWR band width at 2:1 was 350 KHz instead of 300 KHz. The center "hump" was 1.7:1 or less. I was trying to get good SWR at 3705, 3837, and 3885. That turned out pretty good. I may even try it with a 40 meter dipole later.

Since I had re­moved the Jet­stream style 80 through 10 high­er bands, I need­ed cov­er­age of the bands on a se­parate an­ten­na now. See Fig­ure 6 for the im­prove­ment of the dual band configuration from the Jet­stream multiband configuration. This is the result of my first attempt, a dual band 20 and 10 meter dipole fed from a common feedline. DO NOT attempt to use a 15 or 17 meter dipole with this combination, since it will detune both of the other antennas. You can see the improvement from separating the 20 and 10 meter dipoles from the 40 meter dipole; the SWR band width is dramatically improved.

[Raw Data: Dual 20 & 10 vs Jetstream]

At some point, I had new anchors installed in the trees. So I installed the 20 meter dipole at 35 feet, and the 10 meter dipole at 30 feet. I used SEPARATE FEEDLINES, so that these were individual "stacked" dipoles at optimum height. WOW! The new SWR curves are below. Keep in mind that the "jetstream" all band configuration, the dual band configuration, and the separate individual configuration ALL deliver monoband performance. But the SWR now allows completely tunerless operation on all of the band in each case. This experiment is intended to demonstrate to you that IF you have the space and supports for individual dipoles at optimum height, operation is easier. If you do not have the space or supports, the performance is compromised in subtle ways as this experiment proves.

Most commercial antennas specify their band width at the 2.0:1 frequencies. On 20 meters, these monoband dipoles measure 2:1 at 13.380 and 14.775 for a band width of 1.395 MHz. For 10 meters, the frequencies are 27.265 and 30.336 for a band width of 3.071 MHz. This is for thin wire elements, not large aluminum pipes. I defy you to find ANY commercially made antenna that delivers that kind of SWR curve, without the use of lossy resistive components like the T2FD, lossy bazooka trickery, or smoke and mirrors advertising. Significantly, the reactance curves show very little of this component. The resistive portion is NOT 50 ohms, since an optimal height dipole is more like 70 ohms, but most radios cope pretty well with resistive loads, especially if they are a little HIGHER than 50 ohms. Many verticals deliver LOW resistive loads (because they are shortened by traps or loading coils) at resonance, which is tolerated less by solid state radios.

Once again, build your own, save money, and get better performance!

THE 20 METER MONOBAND DIPOLE

The orig­i­nal Jet­stream Multiband 80 - 10 Dipole nev­er had cov­er­age of th­ese bands. I put up another se­parate du­al band an­ten­na for the new bands, now that I had a rig (FT-950) that cov­ered them. See Fig­ure 8 for the SWR curves.

WHAT ABOUT 17 AND 6 ME­TERS?

I think you can do this if you op­ti­mize the 6 me­ter per­for­mance as a 3/2 wave and take what you get for SWR on 17 me­ters. I saw some­thing on the web that did this OK. I put up se­parate dipoles for th­ese bands, since they are small and in­ex­pen­sive. The per­cen­t­age band­width on 6 me­ters is 8%, which is pret­ty wide, if you plan to use CW, SSB and FM. It is near­ly as big a chal­lenge as 80 Me­ters, so I de­cid­ed to keep it sim­ple. I may try a bowtie style de­sign on 6 Me­ters or maybe a bowtie on 17 Me­ters and see if the 6 Me­ter 3/2 wave har­mon­ic is sim­i­lar­ly wide band. If you give it a try and it works, let me know.

UPDATE 6/10/2015

This addtional information is in response to an e-mail query about this page.

Wireman is about the same price for center insulator as the inferior ones. All stainless hardware, drip ring, better braid to attach, workmanship excellent.

Ductseal from local electrician supply (brick about $5 for lifetime supply) seals coax connector and is easily removable. Cheaper than the sealing wrap that is the exact same material.

PVC pipe will work fine. I buy the pipe caps to keep the hornets from making nests in them. Also keeps water out so doesn't de tune. I drill a small hole in the bottom to drain water which may enter as it travels on the wire thru the spreaders. You can buy a long piece of PVC and cut it into the various lengths with a sharp hacksaw. Deburr it so the end caps can be removed if necessary.

I recommend 4 ft at the ends if you can manage for between the 80/40. The wider spread, the less interaction and more bandwidth. Then at the 40/20 half that length (2 ft spreader) and the 20/10 will be 1 ft. Make some intermediate spreaders or it will tangle in the wind. PVC is very light, but might consider #12 ga wire for strength.

One other approach if you have room is to do the broadband dipole on 80/75 with separate wires to separate trees about 20 ft or more apart. Better SWR curve on 80 and maybe helps 40 too.

Then do just a 40/20/10 with the multiband in the middle of the two branches of the 80/75. One center pulley and coax for all of it.

If you want a multiband antenna for cheap (don't have to buy a tuner and GOOD open wire aint cheap) that will match or be better than the conventional G5RV this is the bees knees. Easier on your radio too.

Jetstream kit does not space antennas a far apart; only 6 inches. Same deal for the Alpha Delta. Lots of interaction between various bands. Still gonna need a tuner at the band edges unless you cut it for phone or CW and only do one mode.

I use two separate end ropes to the same tree on my installation on Long Island from the 80 and 40 antennas. I put the 20 and 10 on the INNER part of the spreaders to keep them tensioned. That way nothing flops in the wind. This method went thru Sandy without a scratch.

I wind a 6" of bare stranded wire around each antenna wire as it passes thru the spreader to keep it from sawing back and forth in the wind and keep the 20 and 10 meters from losing tension due to slipping toward the center gradually. Drill as small a hole as possible for the wires in the spreaders to keep rain and bugs out. Lay out all the wire on the lawn near the final location and feed the spreaders onto the wire toward the center, then wrap the anchor wires on the spreaders. Rewrap the 6 " anchor wires tightly once you get it all tuned.

15 meters is a "bonus band" that will require a tuner. The length of the 50Ω coax may help or hinder a match. Try inserting a short length jumper (3 ft) to see if the rig's built in tuner will match. The 3/2 wave 15 meter antenna (really the 40 meter dipole) has significant gain and is about 150Ω resistive depending on height. It is essentially a coax fed G5RV scaled for best performance on 25 meters.

For how to build information, construction details and material sources for this project, see my article: Building Dipole or Wire Antennas.