2nd post about homemade antennas

[dime196604]

Ok just had a post a few weeks back about small homemade antennas and i got awesome feedback from you guys on that post but now i'm back with some new questions. what is the best high gain homebrew antenna? or i mean the best higher gain small or stealth antenna? is the dipole the best one to use even though you don't have enough room to have it stretched out so you have to let the sides hang down about two feet on each side? or is there a better antenna i could build to fit in the space? any one with higher gain then the dipole? and mostly any one know how to make the isotron stealth antenna ? it says it does better then a dipole.. any one know how to make one on the CB bands? how to tune it? or know a better homwbrew antenna that is good for small spaces.. thank much to everyone

[231]

Whomever told you the Isotron works better than a dipole is full of beans. Frankly, like any antenna with a coil they are a compromise. In their particular case though, they are a huge compromise! I've known a couple of guys running those on the lower HF bands and believe it or not they work. But compared to a dipole (even a loaded dipole with coils) it wouldn't even come close...especially at the same height. You'd be better off building a loaded dipole or simply bending the legs on the wire to somewhat conform. None of the compromised antennas (that I know about) will show gain.

After all, their gain is measured in one of two ways; Either over a dipole (dbd), or over an isotropic radiator (fictional antenna) in free space (dbi). But the dbi of a dipole is 2.2 dbi compared to 0 dbd. So if they are using a dipole to measure any real gain and none of them show gain over a dipole, wouldn't the dipole be the logical move? I think so. They are easy to make, inexpensive, very effective, and best of all very forgiving to their installation.

If you have room for a loop, that would show a little gain to a dipole. But it's also larger. However, you can conform the loop to the space you have usually. Meaning, you can make it in a square, circle, octagon, etc. If you have the room, that might be worth looking into.

If it were me, I'd be shooting to install a dipole to start with...but follow your own conscience.

[Double D]

Well if you are interested in short efficient antennas, check this one out: [Please login or register to view this link]

['Doc]

Double D,
The author's explanation of why that antenna does so well is also the reason why it isn't going to be a replacement for most antennas. The claim that it has something like '10 times the resistance' of 'normal' antennas also means that the efficiency of it radiating goes down, just like a dummy load. A dummy-load WILL radiate! Just not very efficiently.
The claim that antennas don't have to be 'large' in size (meaning the typical 'normal' size for a particular type of antenna) anymore isn't something new by any means. 'Smaller' antennas have been used for a very long time. Those 'smaller' antennas are possible because of 'loading' to make them resonant. Using a coil certainly isn't the only method of loading! And I'm afraid that 'length' and 'efficiency' are directly-proportional. Meaning as the 'length' get's smaller, so does the 'efficiency' of that antenna. And all of that 'length' stuff is based on wave lengths, not yardsticks.
- 'Doc

(None of this is a 'poke' at you, 'Double D', but at the one who made those claims. No one can change physics. The methods of going about doing something can change though.)

['Doc]

dime196604,
There aren't any 'gain' antennas like you want. At least not without there being 'additions' to them of some kind, which usually means they are not going to go unnoticed, sort of.
There are ways of disguising things, some much easier than others. When that 'disguising' part get's to be more than what it's worth, then it's time to look for some other solution. One of the 'worth' thingys you have to take into consideration is efficiency. There's a 'cut-off' point there, which will be different for who ever is doing it. Almost anything is better than nothing, so I have no idea where your 'cut-off' point would be.
Dipoles are not the most 'picky' antennas in the world, they can be bent into some really unusual shapes and still work okay. They do not have to be 'perfectly' straight or positioned. They can be made into some really weird shapes and still be workable. So can verticals. The 'classical' shapes are the ones found to work the best. There's lots of 'skootch' room in that, they do not have to be the 'best' to work well enough. There's so much variations in that so that the only way you'll know for sure is to try it and see.
- 'Doc

('Skootch' is one of those secret technical words! just so you'll know, you know?)

[goofy]

Im in the process of putting together a moxon. The moxon and the spider beam are the ticket for a "small" base antenna that shows true gain over dipole.

I'd probably actually do the spider beam if somebody would help me with the geometry. With a few online tools and the Pythagorean theorem, I was able to draw up what I wanted to do with the moxon, so that's what I'm doing.

You can replace wire with coaxial cable and make them even smaller.

But as was said, a dipole is a really really good start. It will perform better than any 1/4 wave ground plane, loaded or otherwise. The only caveat is that it is natural to hang them horizontally which is great for DXing, not so great for local chat (although it will still work)

[PoeDunk]

Hmm... after reading the info in the RoomCap antenna, it seems very similar to another one that I am actively working on (but for different applications). It is a "high resistance" antenna but the capacitance of the antenna is cleverly phased to counter that static resistance. It is an ingenious design that seems to fly in the face of all antenna modeling programs until you look closely at the new theory behind it's method.

You can find a ton more information about a very similar antenna if you google "eh antennas" and follow the links to the individual band antenna projects. They even offer a free online calculator to help with the design of this new style of antenna, and free downloadable PDF files with construction tips and measurements, etc.

You really didn't say what your stealth restriction were in this post, but if you happen to be restricted to an attic space, Ive had amazing luck with co-phasing double bazooka dipoles horizontally in my attic space. I used a common trucker co-phasing harness that you might find on any twin antenna OTR truck. The co-phasing coax harness is the key to this one. The coax is not your typical RG58 stuff. It is constructed of specific length 75ohm cables that happen to meet at the right point together to give you a 50ohm input for the radio. You can then couple a length of mini8x coax from the junction point to your radio. The dbl bazooka should be about 8 to 11 feet apart in parallel. Any closer together and you loose the additional lobe enhancements of the second antenna and are just as good as a single dipole. Any further apart and you loose the elongated lobes that the second antenna provides and wind up with a diminished overall pattern.

I personally ran 2 pairs of these in my attic for years. One pair pointed north-south, and the other pair pointed east-west. The only thing to be aware of is the high voltages that are generated at the ends of a double bazooka dipole. You don't want to tie the ends directly to your rafters. Use a foot or so of rope to separate the ends from the tie points. I used an antenna switch to go between the pairs (kinda like having rotating beams without the the hassle and expense).

The difference I found in the cophasing arrangement were most noticiable in DX operatiions. I was able to reach Guam from California with only 100 watts on 10 meters during the worst (i.e. quietest) sunspot cycle in history. When I was only running single dipoles I could barely make it to Hawaii. Personally, my parallel bazooka dipoles were exactly 9'8" apart. I got to that number based on a ton of calculations I had done at the time using the specs of my particular coax. I later found out that I didn't have to be so exact. But that is just how us engineers think.

PoeDunk

[dime196604]

i Am just looking for some thing i couls rig up around my balconey and shoot some DX with...Don't have a lot of room and wanna find what would perform the very best in my restricted space .