View Full Version : Gap HF Antennas
kg4kww
04-23-2008, 03:17 AM
I'm thinking about purchasing a Gap Antenna.
I like tthe fact that the Gap antennas don't require ground radials and that's a plus for the antenna.
What do you all think of Gap antennas?
http://www.gapantenna.com/
It's a lot of trouble to tune, and frankly I think you'd be better off with a hustler 5BTV and some radials.
A vertical with radials is pretty good. Not great, but good. Actually if you have a lot of radials or elevate it it's great. Not beam great, but good enough.
Hi,
Have you ever actually used one of these antennas??? My GAP Titan was the best antenna I have ever used other than yagi's. I worked one hell of a lot of DX on it. Being omnidirectional, I could easily work stations from disparate directions, as there is no rotator to turn. Omnidirectional antennas do have their advantages in contests.
And it is true that they work regardless of ground conditions. However, head the mounting instructions carefully. Most of the mistuning problems are due to people who don't RTFM. If you put the antenna near any large metal object, it will detune. It has to be mounted somewhat out in the open.
They are not traditional verticals, but instead are vertical dipoles fed kind of off center. The antennas have a very low radiation angle that is great for DXing. For local ragchewing however, perhaps a regular dipole fed with ladder line would be better.
The only minus I can think of about this antenna is that it is complicated to put together. And before you buy one, if you plan on working CW on 80M, make certain to order the special cap for the bottom part of the band. The antenna only has about 100khz BW on 80M.
Rob N3FT
A71AN
04-23-2008, 04:15 AM
It's a lot of trouble to tune, and frankly I think you'd be better off with a hustler 5BTV and some radials.
A vertical with radials is pretty good. Not great, but good. Actually if you have a lot of radials or elevate it it's great. Not beam great, but good enough.
My friend, I have an antenna vertical which is desgined for 40 and 80 meter, the swr on 40 is 1:5 which is ok and with the tuner I managed to make a lot of contacts with it on 40, but the swr on 80 is too high above 5:5, that why the gain is too poor on 80, it should have redials, but 8 redials of 21b meters where to place on the roof, more over after putting the redials the swr went real high on 40 meter, that why I have removed the redials, could the redials be mounted while they are rolled off, or could the size be reduces to something reasnoble than 21 meters ?
Thank you my friend
My friend, I have an antenna vertical which is desgined for 40 and 80 meter, the swr on 40 is 1:5 which is ok and with the tuner I managed to make a lot of contacts with it on 40, but the swr on 80 is too high above 5:5, that why the gain is too poor on 80, it should have redials, but 8 redials of 21b meters where to place on the roof, more over after putting the redials the swr went real high on 40 meter, that why I have removed the redials, could the redials be mounted while they are rolled off, or could the size be reduces to something reasnoble than 21 meters ?
Thank you my friend
Use shortened radials. Put loading coils in the center of them...you should be able to get the lengths down to 10m or so. Search the 'Web for information on "loaded dipoles" and use the calculations to derive coil construction data for the center frequency. Remember: A loaded ANYTHING (vertical, dipole, etc) is going to have higher "Q" (and as a result, narrower bandwidth) than its unloaded equivalent. So your 2:1 bandwidth is going to be on the order of 50-100KHz, depending on the method of construction utilized for building the coils.
It's a lot of trouble to tune, and frankly I think you'd be better off with a hustler 5BTV and some radials.
A vertical with radials is pretty good. Not great, but good. Actually if you have a lot of radials or elevate it it's great. Not beam great, but good enough.
Agreed, and agreed.
I have a 6BTV @ 30ft; 4 tuned radials per band...except on 80, where I have 2. For what it is, the thing makes lots of contacts. You aren't going to use it as an NVIS antenna to ragchew with the 75M crowd in the evenings; a tuned dipole is far better for that.
My friend, I have an antenna vertical which is desgined for 40 and 80 meter, the swr on 40 is 1:5 which is ok and with the tuner I managed to make a lot of contacts with it on 40, but the swr on 80 is too high above 5:5, that why the gain is too poor on 80, it should have redials, but 8 redials of 21b meters where to place on the roof, more over after putting the redials the swr went real high on 40 meter, that why I have removed the redials, could the redials be mounted while they are rolled off, or could the size be reduces to something reasnoble than 21 meters ?
Thank you my friend
What n8yx said.
Also, a lot of these verticals are tuned from the factory to work with no radials. You'll have to adjust them to use radials.
WA7OET
04-23-2008, 01:22 PM
What n8yx said.
Also, a lot of these verticals are tuned from the factory to work with no radials. You'll have to adjust them to use radials.
Incorrect. The GAP is a vertical dipole, the Hustler is a quarter wave monopole. Two completely different designs/theories of operation.
That being said, you would be far better off building your own antenna instead of paying 3-4 hundred dollars. You will learn a lot of antenna theory and have the satisfaction of using something that you built yourself. (old fashion ham radio)
you would be far better off building your own antenna instead of paying 3-4 hundred dollars. You will learn a lot of antenna theory and have the satisfaction of using something that you built yourself. (old fashion ham radio)
That, or scrounge the hamfests and come away with a complete Hustler vertical for $40 ... :D
I had a Titan at one time.
Assembly was OK, the instructions left some to be desired.
It has to be guyed. Sure it flexes but it hard on it and the hardware will work lose if you don't guy it.
The factory hardware was somewhat cheap and I bought better stuff at the hardware store for it before I put mine up.
Performance was in my opinion less than average ground mounted which is the preferred method for this antenna.
I think they Butternut HF9V for the same money is a better antenna by far but it does require radials.
I know many that have had the Butternet products and been very happy with them.
I'm thinking about purchasing a Gap Antenna.
I like tthe fact that the Gap antennas don't require ground radials and that's a plus for the antenna.
What do you all think of Gap antennas?
http://www.gapantenna.com/
I know several people who love the GAP antennas, and many more who don't. There are a variety of reasons.
I know my wife's late uncle had one on the back of their house and did quite well with it & a TS-830S.
Like any antenna, you have to read and follow the directions on assembly. Several of the people I know who have or had problems with their GAPs don't always follow directions well. Coincidence? Hmmm.
I've also helped a few hams take down and/or move GAP's. Mechanically, they can be tricky to dismantle for moving, and I've heard some horror stories & success stories. So if you're buying a used antenna and moving it, be cautious.
Personally, I'll stick with my Butternuts. YMMV, VWPBL(STn)
73
WB2WIK
04-23-2008, 03:44 PM
I had a Titan at one time.
Assembly was OK, the instructions left some to be desired.
It has to be guyed. Sure it flexes but it hard on it and the hardware will work lose if you don't guy it.
The factory hardware was somewhat cheap and I bought better stuff at the hardware store for it before I put mine up.
Performance was in my opinion less than average ground mounted which is the preferred method for this antenna.
I think they Butternut HF9V for the same money is a better antenna by far but it does require radials.
I know many that have had the Butternet products and been very happy with them.
::I've pretty much found that, too. The Titan is a great antenna only if you don't have other antennas up at the same time to compare it to. I've installed probably six or seven Titan-DX verticals over the years and did the recommended instruction manual re-write for GAP because the instructions were terrible. The Titan really needs to be isolated from its mounting mast, unless you get very lucky. It comes with a preattached feedline internally with a "pigtail" protruding from near the bottom and you use a barrel adapter to connect the station transmission line. If that barrel adapter or the PL-259 shells happen to touch ground (mounting mast) accidentally, it can throw the entire antenna out of resonance. Very strange antenna indeed.
In any case, I agree the HF9V Butternut is definitely a better performer, 100% of the time, in any situation -- and of course, it does require radials! The simple HF6V (family) from Hustler is also a better performer, with radials. The K7LXC/N0AX published report on vertical performance, which is well documented with photographs of all installations as well as substantial field strength (empirical) analysis, indicates the GAP Titan to be a poor performer compared with these others.
However, it's a lot better than no antenna, and also much better than the unassembled antenna in the garage!
WB2WIK/6
However, it's a lot better than no antenna, and also much better than the unassembled antenna in the garage!
...and for darn sure it's better than an Isotron...
WB2WIK
04-23-2008, 04:02 PM
...and for darn sure it's better than an Isotron...
...or an "E-H" antenna! Or many others.
W5HTW
04-23-2008, 06:31 PM
I ran a Gap Titan V for about ten years. Finally the wind had done enough damage I took it down and sold it.
If radials is a concern, the GAP is an excellent antenna, for it can be mounted on a short stub at ground level (mine was about three feet above the groun) or on a mount on the roof of your house or garage, or even on top of a tower.
Another feature is the Titan covers 80 through 10, including WARC, with no tuner required. I also used mine on 6 meters! And with no tuner!
There ARE better antennas. But for ease of mounting, the lack of radials (in fact radials are detrimental to the Titan), angle of radiation, and all band tuning, it is a very good antenna, in my opinion. And soil composition is not a factor at all.
The GAP is a vertical coaxial dipole. There are several precautions. First, you MUST follow the manual, especially where the feeding of the coax is concerned. You need to take the antenna down to change the top mounted capacitor, which selects which portion of 80/75 meters the antenna works on. Gap makes a hinged base that makes that easier, but the big counter poise still has to be removed to tilt the antenna over.
In high wind conditions, such as we have here, the detuning stubs simply will not stay in place. I put stainless steel hose clamps everywhere I could, and even used nylon rope to hold them in place, with some degree of success, but not totally.
Yes, if absolutely has to be guyed, though I have seen a tower mounted one that is not. That is in the city, though, where trees block the wind a lot. You don't have to use the GAP guying kit. I connected three nylon ropes, using a stainless steel hose clamp, about 2/3 the way up the antenna. They held for years.
The antenna is defintely insulated from its support mast. It MUST be. They supply the insulators. Use them.
Assembly is complicated but not worse than some other verticals. I recommend using stainless steel screw type hose clamps at every junction. They use 6061 aluminum, and in a windy environment, the sheet metal screws will not hold the antenna together for very long.
I had an early problem with mine, and GAP went WAY out of their way to assist me. At no charge, of course. There is no way I could fault their support, and I know I cost them money!
Yes, the antenna must be installed far away from any metallic objects, including fences, roofing with metal content, pipes, towers, electric wires. Metal within about 30 feet or so will affect the operation of the antenna.
I have even considered buying another one. Were I to look at a vertical, that is the one I would choose.
Ed
KA4DPO
04-23-2008, 06:32 PM
As one who has owned and used a 4 BTV and a Butternut antenna I would have to say that the Butternut way out performed the hustler by a wide margin. Both were properly tuned with a large radial field and each one presented a low SWR to the transmitter but the Butternut was significantly better than the Hustler.
Having said that, I would never buy a commercial vertical again. I would build my own from easily available aluminum tubing and use a home brew matching network. The one thing I have learned about verticals over all these years is that you MUST have plenty of radials to make them work properly. The no radial dummy loads that are sold as antennas are nothing more than gimmics equivalent to the Isotron.
A 32 foot radiator with 60 or more 32 foot radials and a proper matching network will operate on 40 and 15 meters better than any store bought multiband contraption you can buy. It will also work like a champ on 20 meters but at a half wave it's voltage feed so you have to use a parallel tuned, link copled network to deal with the high Z input.
w3dub
04-23-2008, 07:56 PM
What GAP doesn't tell you in the fine print they still recommend the radials anyway. You could run any vertical without radials, including the Hustler 4/5/6BTV and get okay performance. I haven't seen actual comparisons between the GAP vis a vis the Hustler with no radials, but I'm willing to bet the difference is not much.
Go save your money and scoop up a Hustler 5BTV. If you're worried about radial placement (as I was), shoot me an e-mail and I can provide you with some pointers to deal with those issues that I've found has worked from my experience.
AC0FP
04-23-2008, 08:30 PM
Incorrect. The GAP is a vertical dipole, the Hustler is a quarter wave monopole. Two completely different designs/theories of operation.
That being said, you would be far better off building your own antenna instead of paying 3-4 hundred dollars. You will learn a lot of antenna theory and have the satisfaction of using something that you built yourself. (old fashion ham radio)
OET,
A very good point. I was going to post some information I gained from testing UHF antennas on a 3 meter antenna test range but I decided the flames I would get were not worth it. At least now I know there is someone who will understand. So, donning flame proof clothing, here is what I found out.
I wanted to build a higher gain antenna that would replace the monopole antenna on a held held radio. I knew that a well known antenna manufacture (won't mention the name but their trademark features a picture of daffy duck) sells 1/2 wave rubber duck antennas which do not require a ground plane. I believe this design is sometime called a bazooka, as the center connection is a 1/4 wave monopole and the other half of the antenna is a 1/4 wavelength tube slipped over the coax feedline and soldered to the coax shield at the feed point. There is a BNC connector on the other end of the coax. I built the antenna and tested it connected to a hand held radios PC board. The gain measured on the antenna range was -6 dBd. I couldn't believe it the VSWR was < 1.5:1and it didn't work, or a least its radiated gain was crap.
I came back the next day after "sleeping on the problem". I set up the commercial 1/2 wave antenna on a good ground plane and measured the gain, again I got -6 dBd. I immediately removed the ground plane so the antenna was suspended in air by the coax cable connection (no ground plane) the new gain was 0 dBd, a perfect dipole.
Moral of the story, if the antenna design does not require ground radials don't add them as you will screw up the antenna design and its gain.
73,
Frank:)
PS: I have a 20 meter center fed 1/2 wave vertical doublet, I made, its fed in the center with 450 ohm window line. You can find an almost identical antenna documented on W4RNL's website.
KA4DPO
04-24-2008, 12:46 AM
OET,
A very good point. I was going to post some information I gained from testing UHF antennas on a 3 meter antenna test range but I decided the flames I would get were not worth it. At least now I know there is someone who will understand. So, donning flame proof clothing, here is what I found out.
I wanted to build a higher gain antenna that would replace the monopole antenna on a held held radio. I knew that a well known antenna manufacture (won't mention the name but their trademark features a picture of daffy duck) sells 1/2 wave rubber duck antennas which do not require a ground plane. I believe this design is sometime called a bazooka, as the center connection is a 1/4 wave monopole and the other half of the antenna is a 1/4 wavelength tube slipped over the coax feedline and soldered to the coax shield at the feed point. There is a BNC connector on the other end of the coax. I built the antenna and tested it connected to a hand held radios PC board. The gain measured on the antenna range was -6 dBd. I couldn't believe it the VSWR was < 1.5:1and it didn't work, or a least its radiated gain was crap.
I came back the next day after "sleeping on the problem". I set up the commercial 1/2 wave antenna on a good ground plane and measured the gain, again I got -6 dBd. I immediately removed the ground plane so the antenna was suspended in air by the coax cable connection (no ground plane) the new gain was 0 dBd, a perfect dipole.
Moral of the story, if the antenna design does not require ground radials don't add them as you will screw up the antenna design and its gain.
73,
Frank:)
PS: I have a 20 meter center fed 1/2 wave vertical doublet, I made, its fed in the center with 450 ohm window line. You can find an almost identical antenna documented on W4RNL's website.
Flame on....
I guess someone forgot to tell you that an end fed 1/2 wave antenna does not require radials because it represents 180 degrees of current distribution. A quarter wave antenna is only 90 degrees and so requires a 1/4 wave radial system to provide the additional current path. That works at any frequency, even light.
kg4llq
04-24-2008, 01:32 AM
I've used a Force 12 Flagpole vertical since 2003 & have been well pleased. It comes with 4 radials (about 20 ft long, if I remember) but I added 16 more for a total of 20 of various lengths. I've seen charts where using more than 20 radials is the point of diminishing returns. Anyway, this vertical is less than 1.5:1 SWR on 20 meters. I get fair results on 40 meters, good results on 30, excellent on 20 and good on up the HF band to 10 meters. I even use it with a VHF tuner to rag-chew on the local 2 meter repeater! Anyway, for a price of about $150.00 (that's a guess--when I got mine it was less than $150) it's a good deal. Force 12 has a loading coil just for 40 or even 80 and you can buy additional 4 ft lengths of aluminum tubing if you want. My coax is buried & I just replaced the original with new RG213. Caution: Be sure to run the length of coax as directed in the installation manual and make a choke next to the entrance to your shack. I've worked DX around the world (mainly CW) and even sent out 1/2 watt on 20 meters using my RockMite 20 into Canada. I can't wait for the Sunspot cycle to return so I can operate the RockMite more often. 73 & good luck. Ken
AC0FP
04-24-2008, 01:56 AM
Flame on....
I guess someone forgot to tell you that an end fed 1/2 wave antenna does not requitre radials because it represents 180 degrees of current distribution. A quarter wave antenna is only 90 degrees and so requires a 1/4 wave radial system to provide the additional current path. That works at any frequency, even light.
I know the "flame" is on. I know that 1/2 wave antenna does not "require" a ground plane, I just didn't know that providing one would destroy its performance! As you "guys" would say "my bad".
:p
What is it with everyone and radial phobia? Get the MFJ 2X2 mounting plate and your radials can be 25' on 80M. 250' of wire gives you 10 radials. The wire is #22 and about $2.50 for 100 feet. I am a fat old hamtard and I put 10 radials down in 30 minutes which included wheezing breaks every 5 minutes. The grass covers them up. They can zig zag, and you can put them in one general direction if you have to.
Are we really getting THAT lazy?
w3dub
04-24-2008, 02:50 AM
What is it with everyone and radial phobia? Get the MFJ 2X2 mounting plate and your radials can be 25' on 80M. 250' of wire gives you 10 radials. The wire is #22 and about $2.50 for 100 feet. I am a fat old hamtard and I put 10 radials down in 30 minutes which included wheezing breaks every 5 minutes. The grass covers them up. They can zig zag, and you can put them in one general direction if you have to.
Are we really getting THAT lazy?
People automatically think *lots of space needed* when radials come into the picture. Like you said, you don't need to have them going out 25' straight. You don't even need to bury them if you don't want.. just lay them down early in the spring and by summer the grass will have grown over them. You can't even tell i have radials down anymore...
I know I posted this in another thread but I owned a GAP Challenger for about a year and a half. It is a pain in the rear to tune and is a bit tall. After several days of higher than normal winds my antenna snapped off at the base thus adding one more reason to not like the antenna.
If you want to get a really good vertical I would suggest getting a Butternut HF6V or HF9V. The assembly instructions are straight forward even though from what I remember it was a little tricky to assemble. It was not the actual assembly of the antenna but the measurements of the different sections. You need to be fairly dead on with the measurements as messing up one band will more than likely mess up the match on the entire antenna.
As a performer I was extremely happy with the HF6V and used it for a number of years. The antenna also worked fairly well on 80 meters and was awesome on 40 and 20 meters. I used either that antenna or wire to work over 200 countries only running 100 watts. I had a minimum of 4 radials per band that I used and at that time 20 meters was open day and night so I worked a lot of the south pacific countries at 2am in the morning.
CONSIDER THE BUTTERNUT !
Get a HyTower and be done with it...
Hi,
Have you ever actually used one of these antennas??? My GAP Titan was the best antenna I have ever used other than yagi's. I worked one hell of a lot of DX on it. Being omnidirectional, I could easily work stations from disparate directions, as there is no rotator to turn. Omnidirectional antennas do have their advantages in contests.
And it is true that they work regardless of ground conditions. However, head the mounting instructions carefully. Most of the mistuning problems are due to people who don't RTFM. If you put the antenna near any large metal object, it will detune. It has to be mounted somewhat out in the open.
They are not traditional verticals, but instead are vertical dipoles fed kind of off center. The antennas have a very low radiation angle that is great for DXing. For local ragchewing however, perhaps a regular dipole fed with ladder line would be better.
The only minus I can think of about this antenna is that it is complicated to put together. And before you buy one, if you plan on working CW on 80M, make certain to order the special cap for the bottom part of the band. The antenna only has about 100khz BW on 80M.
Rob N3FT
I have used one. My father-in-law has an Eagle at his lakeside cabin, roof mounted. Decent enough but not any better than a 5/6BTV roof mounted. For sure not worth it at twice the price.
Now, lets talk about assembly instructions.
The GAP assembly instructions are worse than pitiful. They looked like a sixth generation photocopy on a copier that hasn't had a fuser changed in five years. They could stand to take some technical writing classes as well.
Let's compare assembly times.
GAP Eagle 1.5 hours, Hustler 5BTV 20 minutes.
They are overated and overpriced for what they are.
just lay them down early in the spring and by summer the grass will have grown over them. You can't even tell i have radials down anymore...
Yep. My vertical has RG-8 I layed across the yard (70') and I made a dozen "U" lawn staples from anodized coat hangers. Not only can't you see the radials but you can't see the RG-8 now.
WB2WIK
04-24-2008, 05:46 PM
I know I posted this in another thread but I owned a GAP Challenger for about a year and a half. It is a pain in the rear to tune and is a bit tall. After several days of higher than normal winds my antenna snapped off at the base thus adding one more reason to not like the antenna.
::If you "tuned" the Challenger, that's a mistake because there's actually nothing to tune. The element (tubing) lengths are preset and not adjustable. The tap points for the wires on the stub tuned elements are fixed locations and not adjustable, and those element lengths are fixed and not adjustable. I've installed five Challengers over the years and never tuned anything! The only "tunable" part is which capacitor you use in the top of the main vertical mast, to set the 80m resonance. And once that's installed, it's not adjustable either. So, how do you "tune" a Challenger?
I agree it ain't self-supporting in strong winds. I used lightweight rope guys attached just above the center insulator to guy it in four directions, otherwise I'm sure each installation would have failed. My first installation failed after 3 years anyway, because birds pecked at the insulated wires that connect the stubs and broke the wires...had to take it down to replace those, and next time used SOLID #8 copper instead. They can't peck through that!
WB2WIK/6
AC0FP
04-25-2008, 10:48 PM
::If you "tuned" the Challenger, that's a mistake because there's actually nothing to tune. The element (tubing) lengths are preset and not adjustable. The tap points for the wires on the stub tuned elements are fixed locations and not adjustable, and those element lengths are fixed and not adjustable. I've installed five Challengers over the years and never tuned anything! The only "tunable" part is which capacitor you use in the top of the main vertical mast, to set the 80m resonance. And once that's installed, it's not adjustable either. So, how do you "tune" a Challenger?
I agree it ain't self-supporting in strong winds. I used lightweight rope guys attached just above the center insulator to guy it in four directions, otherwise I'm sure each installation would have failed. My first installation failed after 3 years anyway, because birds pecked at the insulated wires that connect the stubs and broke the wires...had to take it down to replace those, and next time used SOLID #8 copper instead. They can't peck through that!
WB2WIK/6
In the above mentioned case, just how was the vertical "tuned"?
After doing a little research I find several "posts" on "eham" recommending vertical dipoles. Of course you can find virtually anything recommended on "eham".
My experiments indicate that if your going with a vertical dipole do not add a ground plane, which was the message I was trying to get across with my earlier "post".
73,
Frank:)