Log Periodic Antenna

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daveleonard

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I will be getting my ham ticket soon so I am doing research on antenna. Where I live, on a tiny island in the Bohol Sea, I am pretty much isolated. Is there a log periodic antenna that I could use on HF and Two Meter?
A multiple band vertical for HF has poor harmonics and for financial reasons I just want to use one antenna with a tuner and an antenna switch between my transceivers and the antenna. Is this possiblr or is it beyond the ability of the tuner to make resonant hf and fm?
Thanks, Dave
 

krokus

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While there might be an antenna that will fit your request, it will be less than optimal. Go with an HF antenna and a separate 2m antenna.

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902

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There are log periodics for HF, but a separate 2 meter antenna would be the best arrangement. THIS antenna goes from 40 meters to 10. Here is my dream antenna system, although it has moving parts and may require preventative maintenance.

I like these for 2 meters.

Considering your location, and being an avid 6 meter DXer, I would love to see you choose a configuration that could put you on 6 meters, too.

Don't put up a screaming antenna only to feed it with garbage cable. If one were to spend the money for the antennas above, they'd be well served with running 7/8" LDF cable to the rotor, then something flexible (maybe a loop of LMR600 1/2" coax) from there up to the feed point. Remember your grounding and bonding.

You can have the best radio equipment money can buy, but your antennas are what makes for a good station.
 

LtDoc

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I think I would have to agree that a single antenna isn't very practical for all band coverage. I also don't think you would be using all of those bands on your island/Philippines, but never having been there I can't honestly say.
Wouldn't something like that log-periodic be nice? But the 'catch' to them, e$pecially the very large ones, isn't the antenna but all the $upporting $tructure/equipment required.
Your first antenna(s) are very seldom ever the last one(s) you will have. As you gain experience and knowledge things will change, if only from curiosity. You would do well to find out what other hams in your general area are using, and why.
Have fun.
- 'Doc
 

N1BHH

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The HF Log Periodic antenna is expensive and well out of reach for the average ham and requires a rather robust tower and rotator system. Your best bet fot HF is an off center fed dipole. It gives you multiple band operation and can easily be hung from trees in the yard. I build my own, it's much less expensive than most commercially available versions. You must use a current balun (4:1) for an antenna height of 25-50 feet, 5:1 for 50-65 feet and 6:1 for 65 feet on up to account for feed point impedance.A good read on the OCFD (or Windom as some call it) is here: Windom Antenna Home Page, and Handbook

You may also purchase one from them if you wish, just go to their home page and look.
 

WB4CS

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If someone could figure out how to make a 160-2 meter antenna that's compact in size and efficient and resonant on all amateur bands they would be one very rich person. In other words, if such an antenna existed we'd all have one.

I'll second what others have said. Focus on a good HF antenna and a good 2 meter antenna separately. I'd even go as far to say to focus on a good HF antenna that is most resonant and efficient on the HF bands you want to operate on. An all-band HF antenna works okay on most bands, but works great on none of them. Unfortunately it's the laws of physics and that's hard to change.

A G5RV or OCF dipole is a good start. Also a ground mounted vertical like a Gap Titan is another good place to start. Or if you have the room, resonant dipoles for each band you want to work would be even better. Of course, if you have the funds, a 100 ft tower and a beam for each band would be even better. The log periodic is a great antenna, but will require a good tower to use. For the cost of most log periodic beams, you'd get much better performance with beams designed for specific bands instead of all of them.
 

prcguy

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I think the best compromise for an HF wire antenna is the 94ft center fed ZS6BKW dipole which uses about 40ft of balanced line as a critical tuning element. This antenna is a cousin of the G5RV but actually has a good match on all bands from 40 through 6m except for 15m. It also radiates really well on 80m and 15m with a tuner since its just long enough on 80m to be only a tiny bit down from a full size 1/2 wave dipole.

The offset center feds work fine also but you would need the 135ft version to work 80m where the ZS6BKW does 80 and fits more residential lots being 40ft shorter. The 40m on up offset version is only 66ft long and most people can handle that.

I had a GAP Titan and found it to be slightly better than a dummy load with a wire attached. I bought it to supplement some low dipoles I use for NVIS and was hoping the Titan would put out a better DX signal but it turns out the low dipoles worked much better for DX. The Titan had an ok match everywhere but just did not perform well.
prcguy

If someone could figure out how to make a 160-2 meter antenna that's compact in size and efficient and resonant on all amateur bands they would be one very rich person. In other words, if such an antenna existed we'd all have one.

I'll second what others have said. Focus on a good HF antenna and a good 2 meter antenna separately. I'd even go as far to say to focus on a good HF antenna that is most resonant and efficient on the HF bands you want to operate on. An all-band HF antenna works okay on most bands, but works great on none of them. Unfortunately it's the laws of physics and that's hard to change.

A G5RV or OCF dipole is a good start. Also a ground mounted vertical like a Gap Titan is another good place to start. Or if you have the room, resonant dipoles for each band you want to work would be even better. Of course, if you have the funds, a 100 ft tower and a beam for each band would be even better. The log periodic is a great antenna, but will require a good tower to use. For the cost of most log periodic beams, you'd get much better performance with beams designed for specific bands instead of all of them.
 

LtDoc

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I won't try to say what your 'best' antenna would be, too many variables in that for any practical purpose. Your QTH is going to be in 'demand' so while you would naturally want the best you can get, don't worry too much about 'best'. A multi-band antenna isn't the simplest thing in the world but it's also not the most difficult to put together. A 'fan' dipole is about as simple as it get's. Would it be suitable for you? Beats me, but it sure could be.
- 'Doc
 

N1BHH

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The G5RV and the ZS5BKW antennas are touchy to tune if you don't know what your doing, not good as a starter antenna to be honest. Don't believe all the hype you see about those. You also don't have to put your antenna up in a straight line. If you have only 100 feet of space, get the feed point as high as practicable and let the ends droop down.

You can even run any dipole as a flat top with the ends hanging straight down, or even zig zagged around the yard, of course as high as is practicable. Don't think with your antenna being 20 feet up to work well. Trap dipoles, parallel dipoles, fan dipoles, all are good ways to learn antenna theory. Loaded dipoles work really well too in small spaces. Just do a Google search and you'll find plenty.
 

prcguy

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There is a lot of hype about the G5RV since it was designed as a 20m antenna with a little gain but is sold as an all band antenna. Its works by virtue of being big enough for 80m and fed partially with balanced line. The ZS6BKW was computer designed as a multiband antenna and if you have space for it and can deal with routing the 40ft of ladder line before the coax transition, its the best I have found for a single HF antenna solution in 30yrs.

Wire antennas work fine 20ft high if you understand the limitations, its really good for NVIS on 80-60-40m and I can also work coast to coast on all bands with 100w with a 20ft high antenna. Higher is better but put up whatever you can.

I have to ask when someone puts down a particular antenna, have you ever tried one and compared to others?
prcguy


The G5RV and the ZS5BKW antennas are touchy to tune if you don't know what your doing, not good as a starter antenna to be honest. Don't believe all the hype you see about those. You also don't have to put your antenna up in a straight line. If you have only 100 feet of space, get the feed point as high as practicable and let the ends droop down.

You can even run any dipole as a flat top with the ends hanging straight down, or even zig zagged around the yard, of course as high as is practicable. Don't think with your antenna being 20 feet up to work well. Trap dipoles, parallel dipoles, fan dipoles, all are good ways to learn antenna theory. Loaded dipoles work really well too in small spaces. Just do a Google search and you'll find plenty.
 

902

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Whomever the end-user is will need to clearly define whether the antenna's going to be used for NVIS (local, more or less) or for low-angle of radiation (DX) operations. I've got a B&W 90 ft. folded dipole that, at its highest, is about 25 ft. off the ground and slopes downward on the sides, one side to a fence, the other side to a vent pipe. I have pretty much statewide coverage on it, which is what I needed for it to do, but this is not a good configuration for working DX. I've got a DXE 6BTV vertical with traps for two additional bands on it, which performs well for DX. Not as well as a monobander up 100 ft. (maybe someday before I die, if ham radio is still around), but better than the B&W. And, forget about working region-wide (300 mile radius) on the vertical. It's just the wrong antenna most of the time.

Different tools for different jobs. Fill your toolbox with good tools and you can do just about anything.
 
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