I brought up GAP Eagle antenna for 3 weeks.
Results are disastrous
TOS: 1/1 27.985
1/1 25 .125
1/1 21. 475
1/1 17.985
1/1 14.480
1/1 7. 325
Completely out of amateur band !
GAP technology produces highly efficient, wide bandwidth performance. As a result, no tuning is required in most amateur installations. This manual is organized to minimize the amount of time necessary to assemble and install your GAP vertical. It is recommended that you follow the instructions and use the figures as a guide. Gain of GAP Tital DX compared to monoband reference antenna:. 80 meter results will be forthcoming. Band: 10m 15m 20m 40m 80m Titan DX, Average -11.0 -7.8 0 -7.6 n/a Relative Gain, dB Reference Ant 4.89 4.68 4.54 4.62 n/a Gain, dBi. Mounting a Ham Radio Antenna in backyard.
Having verified everything I asked via email to gap antenna where could be
located the problem.
It makes fif*** days that I am waiting for the least sign of life of this
society....
If someone already had problems with the Eagle, I thank it by advance to
help me and to give me advices because I have the impression that this
antenna functions as well as the customer service of at Gap antenna!
Best 73 es Dx
Frank **F6BLP**
Perspectiveson GAP
The contents of this web pag is an accumulation ofcomments received from QRP-L members concerning their experiences with GAP antennas. I too have a GAP antenna (Titan) and enjoy it very much. I found this dialoginteresting and useful to me in understanding my antenna's operation and performance ...and thought others could benefit too.
73, George N2APB
PS: The information presented here is notguaranteed to be correct, nor is it endorsed by GAP Antenna Products. Antenna discussionsare usually embellished by folklore and biased by personal experiences. Use thisinformation at your own risk! ;-)
GAP DESCRIPTION
The Gap vertical antennas are all simply dipoles, but verticaldipoles using low loss linear decouplers for loading the different bands. These decouplersare akin to stubs of open wire line we have used for years as matching devices on varioustypes of ham antennas. They just look more exotic when one side of them is the verticalmast itself. They effectively form capacitors to shorten various parts of the tubing toresonate on the higher bands.
The use of the asymmetric elevated vertical dipole is a common Broadcast Band antenna inplaces such as Argentina, and a paper on such appeared in the USA IEEE AntennaTransactions publication some years back. I got a copy of this paper from the Gap booth atHam Com one year . For Broadcast work, you want to minimize ground losses, and have a goodpattern in your coverage area, which the vertical dipole brings without investment inradial systems and ground screens. When you put the (40M) counterpoise wheel on the bottomof the Gap Titan, you end up with not needing the same length each side of the centerinsulator. Inside the Titan, (and I think other Gap models), there is a coax stub forloading on the lowest band. To make the coax stub fit the space inside the tubing, youhave a capacitor across its upper end, with one side and one side of the coax tied also tothe upper dipole end. This matches the antenna to your feed for 80M use over a greaterthan 100 kHz band. Other bands are full coverage. (less than 2:1 SWR)
Does it work? Yes indeed. As long as it is not coupling to something in the near field itseems to bring a lot of nice QSO's and DX with its low angle characteristic. It is stuckon a TV mast 6 feet above my back yard. As a bonus, I have enjoyed good short skip QSO'swithin the state, or in nearby states on 20M, where short skip was rare in the days I usedlow dipoles on 20M. I have heard of interaction as with any vertical, if you havesomething like a metal flue chimney nearby of a resonant length like 30M quarter wave. Itsbandwidth on 80M exceeds the specs, thus I have not used a tuner for any band. It is fullband coverage on 40M and up, and a tuner is not even recommended. It is quite study,having survived 45 mph winds that I was able to document, and more recently, some straightline winds that felled taller trees and limbs all around it during the Jarell TX tornadosup the road from me. The bottom tubing is triple walled, and thus requires a couple of bigfolks to walk up, or three ordinary folks like most of us.
I had an 'all band' Hy Gain coil trap vertical before with ineffective groundsystem. (I have mostly rocks under thin soil). The Gap works much better, although a homemade vertical could be made, for less money IF you had a source for the aluminum tubing.(A BIG IF these days!!) If your time counts for something, Gap solves the all band problemwith a minimal investment of time. However, I would like someone who has the time tosometime create a home made vertical dipole set for all these bands, and see if theperformance is as good or ? I suspect the use of large tubing really is the full bandcoverage secret, and just wire verticals hung from tree limbs might not equal that aspect.But, one could use a cage of wire, and solve that issue.
Hope this inspires some antenna experimenters. I did not hear about any Gap beams at HamCom this year and I always ask if I can be a beta-test site when I see Richard! I thinkthe Sommer beam does use this type of loading/decoupling for band changing. That is amighty beam, and some day, if > I ever get the space----
72 Stuart K5KVH
rohre@arlut.utexas.edu
The Gap Titan is intended to cover all bands above 40 M with 2:1 swrat ends of the coverage, and very low swr in each band. No adjustment is needed for mostinstallations, save the 30 ft. wire counterpoise.
there is an adjustment for the counterpoise wire length to move yourbest swr point on 40M around. Of course, as stated in the instructions, a capacitor on theend of the coax stub inside the mast sets the 100 kHz segment of coverage for 80 or 75 M,and you have to have the cap for the section of band of interest.
The outside the vertical dipole mast, linear decouplers are lengthsof open line, forming stubs on the outside of the mast, using the mast as one side, andthe rods as the other for the higher than 40M bands. One of these has a screw andtelescoping section allowing fine tuning. I think someone on the list some years backmentioned what band this adjustment was for, and it was either 30M or 15M I think. CheckGap Titan in the archives of QRP-L. Check the total length of the rod that adjustablepiece is on, and see on which band it is closest to quarter wave. (I think it is possiblethat some rods affect two bands, ie 12 and 10M are probably one rod.)
One could fashion a new piece of aluminum tubing to slip onto anyrod end, to lengthen it thus lowering or raising frequency, while observing the effect onSWR. Try it on each rod in turn, until you get an effect on 15M where you want lowerresonance. That should define the rod you need to adjust. The effect you get on the SWRvs. frequency, might indicate that a lengthened rod raises the resonance, but that is OK,you will have some effect and be able to determine which way to go for your desiredresult.
Another point is that I believe the antenna was said to be 3 metersoff ground, close to a resonant quarter wave on 15M, and thus, try changing the antennaheight by using more base pole, or less to possibly affect 15M results. Mine is about 2Moff earth, and works over all of 15M very satisfactorily, but then I do not mind 2:1 swr,as its effect on DX is negligible!
Finally, although I never checked this, as 40M is 1/3 of 15 M,perhaps the changing of the 40M counterpoise interacts with the 15M resonance as well? Itmight be worth an experiment to see if some compromise setting of the 40M wire will helpyour 15m resonant point.
Most of the Gap Titans I have seen or heard on the air work verywell indeed without any adjustment except the 40M wire and the choosing of an 80Mcapacitor at time of set up. I hope the ideas I have listed would help anyone with thistype of linear decoupled antenna. Remember it is an asymmetric vertical dipole. That is,one end is shorter than the other to take into account the earth effect on that endclosest to earth, but other wise it is just a dipole whose band of resonance is changed bystubs parallel to it.
Hope this helps,
Stuart Rohre K5KVH
rohre@arlut.utexas.edu
Just had to add to the satisfied Gap antenna owners, andspecifically the Titan model, the first all new commercial vertical I bought outright.(Others have been used, or club owned, etc.)
Really surprised at the comment from the 6 call who had a'flimsy Gap' and bad experience. Could not have been a Titan model!
However, for the education of those wondering about the models, Ihave worked with a friend and put up one of the earlier models for him some 7 years? ago,which had a V (five) in its model name. It was about the same weight as a Hy Gain 18 AVT Ihad up for a few years, which was replaced by my Gap Titan. Also, the earlier model Iwould guesstimate was about the weight and construction of R5's and R7's, (Cushcraft),which I helped friends and Field Day crews put up. (R5 &7 and the MFJ's don't coverall of the bands like 40M and 20M where the Titan does.)
Now, when I got a Titan DX model, I got the surprise that it was theheaviest vertical I had ever handled! That was because the lower half is a multiple wallaluminum tube of Aircraft grade.
It is an Asymetrical Vertical Dipole, as the article in an IEEEEngineering magazine calls this class of dipoles. As a dipole, it has two sections, justlike your horizontal dipole, or a full half wave sloper dipole. Now for a half wave sloperyou don't use radials, right? Nor for a horizontal dipole? Now why would you for any otherhalf wave antenna, that is fed at or near the middle? Once you understand the premise ofthe Gap Titan as a half wave antenna, but just turned 90 degrees to the way we are used tothe majority of dipoles, then you can understand the other design concepts it so cleverlyincorporates. First and formost, at 25 feet it is a tad short to be a half wave on 40 m,or even 20 M. Enter the 'upside down capacity hat', or 'counterpoise wheel' as Ihave also called it. This is the radial like wheel structure the Titan has on its lowerend, which consists of a full quarter wave of wire for 40M as the circumference conductorinsulated on some spokes sticking out from the lower end. Now one end of this wire iselectrically connected to a spoke which is electrically clamped by a mounting plate to thelower end of half of the dipole. That makes the lower part of the antenna below theinsulating gap section something like 45 foot conductor, part vertical, and part coiled asone big turn. The end of the coil comes back and joins its start through an insulatedsection. It makes a substantial radiating device when compared to say the Butternutantennas, (which I have also installed and used), and which are quarter wave verticalsthat do need a counterpoise or radials to 'complete' the other half (of the dipole)they are not.
Now, back to the Titan. It has as much or more bandwidth on 80m asthe Butternut, and much more than the Cushcraft models. True, the total vertical sectionsare 25 feet; but that is a tall Bug Catcher, and the capacity hat or counterpoise wheelmust help as well. No Bugcatcher has this 100 kHz bandwidth without a tuner,conservatively. (Now all you mobile hams don't ge tme wrong, the Bugcatcher is a FINEmobile antenna!)
To make up the 50 ohm match at the insulator between the dipolesections on80M, Gap uses the old tried and true stub technique of a coax quarter wavepiece across the feed point. Cleverly, it is inside the upper tubing, which probablyhelped the tubing survive the tornadic winds my Titan went through during the nearbyJarrell tornado in May. To shorten the amount of stub needed, they place potted ceramiccaps in parallel with the upper end of the stub. One side of that end of the stub alsoconnects to the upper end of the top dipole half tubing.
Now you hopefully have the full picture. A thickwalled lowersection, joined by an insulator to a flexible, but damped for wind vibration, uppersection. It is limber enough to give a bit in a wind, and swing back to vertical. However,with all that weight at the lower half that joins to your pipe mast or ground bracket, ifyou get a wind gust, you have a big heavy lever arm which might loosen your pipe youprovide to anchor in the ground. My TV mast was lighter weight than the Gap tubing, so Ibeefed it up on the side away from prevailing high winds here with a steel angle irondriven in the ground with the TV pole. You could use a field fence post for the sameeffect. Just u-bolt these to the mast you are using to hold up the Titan. My mast is onlysix feet tall, but before I guyed the Titan, a 40MPH gust pivoted the antenna into thebranches of a nearby oak tree. My undersized base tubing just laid over, but the Gapstraightened right up when I pushed back my TV mast, and hammered the angle iron into theground. Nothing on the linear decouplers, (that look like trombone slides), was damaged.(These are the tuning elements that replace lossy traps and inductors with opentranmission line sections to resonate the various tubing sections to the various bands,another innovation of Gap.)
Since that experience, I added three guys of Wal Mart nylon rated at880 pounds each. I just tied them to the tubing near the center insulator with a clovehitch. Nylon does stretch, thus, when it does, I go out and take up the slack with old BoyScout knots. Even if I don't take up all slack, the guys keep things from whipping around,as they did even slack, during the May storm. Next door, a couple trees were detopped. MyTitan is in the back yard, but in my front yard, the winds took 3 large limbs off a 21year old pecan tree. Down the street, one tree was laid over at the base. On estimate waswe had 70 mph winds during the tornadic storm. I think Skywarn calls these straight linewinds, and it looked like a big club had come down the street swatting the trees. But theTitan rode it out just fine. I have never had to retighten any of the clamps that mountits decoupler insulators, nor any of the main tubing joints.
The antenna has been an amazing performer working both the expectedDX, and more frequently than not, close in skip as well, such as New Mexico and the TexasValley on 20M. On 80M, it has worked into Kansas, around Texas, as well as longer skip. Ithas outperformed all my other vertical experiences, while at a low point of the sunspotcycle.
Now, as certainly the price is a factor for some, I would hasten topoint out that you could build your own tubing, (or even wire) vertical dipole, (if youhave a high tree limb to suspend the wire). You could parallel some dipoles beside it forthe other bands, as in the 'sleeve fed' beams where one dipole is fed, andothers parasitically excited. It think you could load the dipole on one end, with thewheel idea, and stub match the central feed, to get on 40 and 80M. I am kind of sorry Idid not know about the asymmetric vertical dipole as a class of common AM Broadcastantennas in South America, before I bought the kit, for I think with some effort, onecould do a wire version for certainly a lot less money.
Finally what swayed me was the materials availability of aluminumtubing was not good in my area, and the time factor. Time is money, even ham time. I paidgood money, but I got good value, and George's clever ideas implemented with me doing somevery minimal labor.
The Gap folks, Richard and George, that you see at the shows, arehelpful and quick to fix things like the loss of some hardware out of my box due toovereager summer UPS help during shipping.
Another local ham friend bought the Voyager, and has great resultswith it on the lower bands it covers. But at 45 feet tall, it was more than I could handlein my small yard. It certainly is to be considered if you are mainly a 160 and 80M type.
Gap Titan Dx Manual
Hey, the whole company signed and sent out Christmas cards thisyear! Now that is a first! Whatever you do, enjoy your antenna!
Stuart K5KVH (not a stockholder, but sometimes wish I were!)
rohre@arlut.utexas.edu
Gang,
As a Titan owner who really dug into its design background, andvisited with the author of its design, I can tell you that each and every part isessential to its overall proper operation.
Gap Titan Dx Antenna Manual
To remove the 'counterpoise' would be to remove allresonance on 40 Meters and would undoubtedly detune other bands. Normally only adjustingthe length of the 33 foot wire on the circumference of the counterpoise is all you do to'tune' a Titan. There was one linear decoupler with an adjustable segment, butmy instruction sheet listed it as factory set.
The Titan is a vertical dipole that is made into an 80M to 10 Mantenna by a couple of clever basics of antenna practice. One is to get resonance on 80Mfrom a 25 foot dipole, they connect a cap loaded stub of coax across the center dipolefeed point. The coax stub is about an electrical wave fraction with its cap, to match 80Mat 50 ohms. Next, to get 40M form this short dipole they add an end element which wecalled a counterpoise, but is really an extension of 33 feet coiled into a circle. That'sright, if you trace its circuit out, it joins the lower end of the dipole, and iselectrically isolated from the radial rods that support it until you get back to the rodthat electrically joins it to the lower end of the dipole. It is insulated from shortingto itself by the nylon line that you adjust to rubber your 40M SWR dip. The dipole sits ona double insulated plate to keep it isolated from your bottom mast. (You provide thesupport mast for elevated mounting.)
The linear decoupler rods are stubs of transmission line in action,and decouple parts of the 25 foot dipole for resonating in each band, 30, 20, etc. up to10M. Not a lossy trap in sight, and a neat antenna! Mine only shows a single upper mastend above the roof line, as it sits 6 feet off the back yard surface. Got my card fromEaster Island operation in 95 today, thanks to a slow buro (burro?) envelope, and that wasdone with the Gap in the pile ups at close of that DXpedition.
The poster has been advised by me to put up a mast high enough toclear the slope of the roof, with the Titan wire portion. I like to call it an upside downcapacity hat, but calling it a counterpoise is easier for most hams to understand itsaction.
I 'suspect' you could deform the rods to have the plane ofthe wheel slanted rather than parallel to the earth level, and it might still work on allbands without tweaking, but I would have to ask the Gap guys at Ham Com. You could thus,make the wheel clear the slope of a gable roof, by almost paralleling the slope.
GL, Stuart K5KVH
rohre@arlut.utexas.edu
You asked about the Gap antenna line. Most of their models areverticals of a type used in South America for AM broadcast antennas, and known as an'asymmetric vertical dipole'. This means, the two dipole halves are not equallysized. One side must vary because of it being closer to earth. With the addition of lineardecouplers, (stubs), for the bands desired; you have a vertical dipole on multiple bands.
Gap does a neat trick with the 25 foot long Titan, that I have. Theyenclose in the tubing a capacitor loaded coax stub, to make it resonate on 80M as well asall other bands 40M and WARC up to 10M. Perhaps the most clever thing is how resonance isobtained on 40M. There is a set of radial rods at the bottom that support a circle ofwire. The 33 foot wire makes electrical contact with the end of one rod only, that joinsit to the main antenna. The wire circle is not completly closed, but has a nylon stringmaking the last few feet of the circle. Thus, you have a full size quarter wave 40Melement in a much more compact area, and it seems to radiate just fine.
When I assembled my Gap, I used an antenna analyzer to see whereeach coupler was contributing a band resonance, and was mystified as to how 40M worked, asnone of them resonated there! When I got the antenna up vertical and went to put on whatlooks like a kind of counterpoise wire circle, I found my 40M resonator in that wire.
Mine is up 6 feet, and works more DX than my dipoles, G5RV, etc. Itis amazingly good on occasion into the next state, but it is low enough take off at sixfeet to be a good DX antenna in this location. I am sure with poor ground we have, (rocky)its dipole being independent of needing earth return radials is a plus. It is a two piece,balanced antenna, although it is an electrical balance, rather than equal dipole halves.What really is helping it out is the Fresnel region out some wavelengths from the antenna.There is a clear shot to Europe, and to Asia, and over the North Pole. However, there arehills to the South, but I still work all the way down South America very well toChile/Argentina, and into the Carribean to the Southeast. There was no tune up requiredlike the MFJ vertical, and only one measurement to set my desired 40M resonance.
No Gap I know of is a cloud warmer! The quarter wave verticalswithout radials may be cloud warmers when you do not have good RF earth under them, or seawater.
Gap has out an interesting new antenna, for the patio confinedantenna farm. It is like the Force 12 compact dipole. They 'squash' the dipoledown and make a cage of the ends to load the thing. I have not worked any yet, but wouldbe interested to hear how anyone has used one.
It is easy enough to make your own parallel vertical dipoles ofwire, and one central support. You might try it. After I spent my money, I realized thereare some opportunities like that going begging. I made a 27 foot PVC mast for 99 FieldDay, that has possibilities for verticals, if you guy it well. It is pretty spindly as youraise it. (I was using it with my horizontal Vee beam leg and two back stay guys.)
Another antenna for all bands not to be overlooked is the invertedextended Double Zepp (IDEZ) I did for field day. With ladder line feed and a mast, it canbe tuned on all bands. Of course, you have to have a big lot for it, for its legs are each159 feet. That is one with lowest band of 80M, and if you make it only 159 feet overall,fed in middle, it is good 40M and up. Gives gain, and is cheap. Insulated ladder line isreasonable from all the antenna cable companies, and larger mail order ham stores. Itseems to work as well as the true open wire, (uninsulated) ladder line that seemsdiscontinued. Saxon did make it but its insulators did not stay on well.
I tried making my own of #24 wire and some plastic clips sold withtwo nails for holding down house romex wire. Take the nails out, and you have a ladderlineinsulator, but if your time is worth money, like most folks, you will soon tire ofthreading these little spaces onto the wires. Been there, made some, it worked, but wasspindly and hard to handle. Give me the plastic covered type, and slightly more loss! Icould never see any measurable loss with window line- the type most available in NorthAmerica. (Check out the Wireman's web page.)
Antennas and QRP kits are the last refuge of the technicallyinclined hams, glad we have a lot of each to play with!
72, Stuart K5KVH
rohre@arlut.utexas.edu
GAP TITAN TUNING
Hi gang, I asked GAP the following, 'Which bands do theadjustable tuning rods cover?'
Their answer was:
The slotted extender by itself controls 12m.
The slotted extension with the 23' extension below it controls 15m.
And, the capacitor (CAP) in is as follows:
Info from BUD, KV7G...
Color Value Freq.
--------------------------------------------------
Black 3300pf 3.5MHz
White 2800pf 3.6MHz
Red 2300pf 3.7MHz
Blue 1900pf 3.8MHz
Green 1500pf 3.9MHz
Clear/Orange 1400pf 4.0MHz
I suspect they are silver mica capacitors.
72, Larry - K3PEG
Hello QRP fellows,
Thanks to all who sent me informations abt the GAP. It was extremhelpful to have this infos while experimenting.
Here are the results:
15m: no problem, adjusted the rod with the long ectention. Now resonant at 21.060 12m: noproblem, adjusted the rod with the short extention. Now resonant at 24.980 17m: noproblem, adjusted the shorter of the lower rods with an additional alu tube, resonant at18.090 20m: The extraordinaire bandwith is a sum of resonant QRGs. I added a piece of alutubing at the longer lower rod. 20 m resonant now at 14.070
10m: that was a little bit tricky. Adding some wire to the wireextention at the rod with the yellow cap had NO result. I added a piece of wire to the NONisolated aluminia tube oposite to the tube, where the short wire extention is connected)That one, with the yellow cap). My wire is abt 1 Meter long. This brought the 10 mresonance down to 28.100, the 40m resonance now was to low. I shortened the longcounterpoise wire by 20cm. Now 40 m is resonant at 7.070 and 10m is resonant at 28.120
All this mods lowered my 30m resonance to 9.990. But because at10.100 the SWR is less then 1.4, this is not a real problem. Only by means of interest Iwill try to add some cm of wire to the lower element of the GAP tomorrow morning.
Summary:
The GAP Titan is resonant at ALL bands now allthough 30m is a little bit low. 20m bandwithis not so broad as it seemed to be first, but it is a multyresonance Problem.
72 and thanks again, Peter