A shortened antenner that works

[WA1GFZ]

Gee my old firebird is near the tower could it be why the LPDA works so well....I'm about 60 cubes less than a rat though but at least a poncho motor and not a oldsmobubble BA

[The Slab Bacon]

Lotz of tiresmoke is a good "burnt offering" to the gods of RF!!

[The Slab Bacon]

you know, its kinda interesting. Quite a few more have downloaded the drawing since youse guys posted the modeling results

[WA1GFZ]

Another interesting thing to see is the performance at 60 feet.

[Steve - WB3HUZ]

If one had the room to use the same configuration but with 90 feet of length, I'm pretty sure the peformance on 75 would be nearly identical to a dipole. It would probably make things much better on 160 meters too. I'll have to do some modeling this weekend.

[WA1GFZ]

Steve,
I did simulation of 160 meters with Frank's antenna 125 feet long to simulate the set up at my new QTH and results looked quite good on 160. Height 60 feet although it will be higher. Lots of reactance on the feed line but #8 wire should handle it.
I did it with 6 foot conductor spacing though.
I need to compare it to the other configurations I dreamed up.
The wire is quite brown now so may ask the neighbor to use his tree now that you can barely see it.

[Steve - WB3HUZ]

Higher up, less ground loss. I'll run some sims at different heights. I often wondered if one would do better with a high, but short antenna or a full sized, but low one. Wonder what the crossover height would be.

Steve,
I did simulation of 160 meters with Frank's antenna 125 feet long to simulate the set up at my new QTH and results looked quite good on 160. Height 60 feet although it will be higher. Lots of reactance on the feed line but #8 wire should handle it.
I did it with 6 foot conductor spacing though.
I need to compare it to the other configurations I dreamed up.
The wire is quite brown now so may ask the neighbor to use his tree now that you can barely see it.

[WA1GFZ]

That would have me sitting in front of the computer another night.
I was all set to string some wire Saturday. XYL called this morning and on the way to my Daughter's driving test at DMV the breaks went to the floor. Guess it will be break job first....oh well all this stupid stuff in the way of playing

[Steve - WB3HUZ]

Ran some sims on the AHE antenna at 60 feet. As you can see in the first image below, the antenna at 60 feet picks up a few dB at the lower takeoff angles and maybe 0.5 dB at the higher angles.

In the second image, you can see the AHE antenna at 60 feet, just about catches up to a full-sized dipole. You would still have some feedline and tuner loss as before, but it would be less too since the resistive component rised from about 11 Ohms to 14 Ohms.

So, as I said before, a 90 foot long version would match the performance of a dipole. Let' see if this is true.

Running the sim with the antenna at 60 feet above ground, the AHE antenna is down no more than 1 dB, and that is at the lower takeoff angles. At the higher takeoff angles, the difference is less than 0.5 dB. (See the third image.) The feedpoint impedance is 36.812 + j385.436. The resistive component is way up compared to the shorter version of the antenna and now the reactive component is inductive (hint, this bodes well for use on 160 meters).

Using W9CF's feedline calculator, at the end of 70 feet of 450 Ohm Window line the Z is 36.40 -j335.59. Loss in the feedline is 0.43 dB. The resistive component didn't change much and at 36 Ohms isn't bad. Let's see how the tuner deals with the now capacitive reactance.

Using W9CF's tuner simulator and plugging in the Z numbers calculated at the end of 70 feet of feedline, tuner loss is 1.1 dB. This simulator is set up for a typical T-type tuner with two series caps and a shunt coil. The simulator finds the lowest loss setting of the components for minimum SWR. In the simulation above, the caps had a Q of 2000 and a max capacitance of 250 pF and the coil a Q of 100.

Adding up all the losses, 1 dB in the radiation pattern, 0.43 dB in the feedline and 1.1 dB in the tuner, a 90 foot long version of the AHE antenna would be about 2.5 dB down from a full-sized dipole. This is not quite equal to a dipole but would be hard to tell the difference on the air in most situations. Considering at higher takeoff angles the difference would be even less, probably less than 2 dB, for most short haul AM QSOs, it's about a wash compared to a dipole.

[WA1GFZ]

Well, First thing this AM go out and look at XYL mobile and see wet frame under driver's seat. Master jug almost empty. no easy task at 30 degrees and snow on the ground. My cheap a$$ turns lazy. Figure jack it up and have a look. Jack broken so go to sears to buy new one. As I pull in there is sears automotive.....HMMMM the ground is friggen cold and don't want to drive all the way to my Dad's for a garage. Wet frame is near muffler so line is way up. screw it into Sears I go.
Guy behind counter figures $125 if it is only one line which sounded real fair.....XYL and I decide this is our christmas present to each other.....So heck $500 is better than a day on my back on frozen tundra. Done.
Jump in truck and fire it up to see change oil light come on....no getting away from that so 1/2 hour under the truck today.
Wind is wipping so might not be good for sending lines into the trees anyway.
and it is such nice antenna wX Today.

[The Slab Bacon]

Your right, Frank!! Who in the hell puts up antennas on a nice warm summer day. You do them in the winter because its too friggin cold for motorcycle ridin!! Who'd want to waste a nice warm summer day when you could be out on the bike. (or plopped in front of the A/C)

[WA1GFZ]

Well Sears wants $280 to replace the brake line to the back of the car. Then the guy says your rear discs are getting thin. just for the heck of it I ask well how much.
Just another $300....I said no thanks. I can replace the pads and discs on that car in 45 minutes because that is how long it took last time....and cost me $100.
After changing the oil in the truck and spraying 4 cans of undercoat all I wanted to do is pace off the distance in the back yard to see how another antenna would fit. Wind was wipping too hard to shoot the line I needed. maybe Sunday.
Yup beach place is shut down now it is radio season

[wa2zdy]

That antenna is 2/3 of a linear-loaded dipole.  A third leg on top going back out to the ends would make it so.

I used a version of same in the attic of my townhouse in NJ.   Mine was 37 feet long to fit the attic, so it had 111 ft of wire total.  Mine was lazy construction though too.   My brother built it for me (and climbed up in the attic with it - I'm disabled and wheelchair bound) from three conductor power cord.   So there really was no spacing between the elements.  I fed it with 450 ohm ladder line and an SGC230 and a Radioworks 4:1 current balun.

It didn't work at all on 160 though the SGC let the rig see 1:1.   On 75 I made a few slopbucket contacts and a few good ones on 80 cw.  On 40, 30 and 20 CW I worked plenty of DX.

No it wasn't a perfect antenna but it did the job for me and damn sure worked better than an attic mounted 37 foot long antenna had a right to.   Here in antenna restricted HOA controlled land I plan on doing the same thing, longer though, between some trees and obviously higher up.

It won't set the band on fire but it'll let me get back to ragchewing and that beats what I've been doing for the past year.

[Steve - WB3HUZ]

Cool antenna. Hope to hear you on the bands soon.

[K7NCR]

OK guys, the "Slab Bacon" special is up and ready for testing at the old "new" homestead. I built it 60 FT per side, 240 feet of wire total, and feed it with my home-brew open wire. The feed length to the tuna is about 45 FT. Center is 30 Ft, and ends are 20 Ft. Its a pretty straight run, from the tower to the utility pole, and a 20 FT mast at site A, see attatched post for a diagram of my lot. Will let you know how it plays, and maybe post a photo or 2. Thanks again!
Norm K7NCR.

[WA1GFZ]

I would be very interested in your results.

[K7NCR]

A half hour or so spent receiving last night proved interesting...
Storm noise on 40, and some on 80, but WOW! 160 was popping! 21:30 mountain time and the NW was booming in. Western WA, OR, etc.
Will post photos as soon as my card reader will cooperate. 
I will probably borrow the club antenna analyzer for some more testing.
Norm K7NCR

[Ed/KB1HYS]

anyone ever try one of these?



http://www.tak-tenna.com/

pretty small, coil wound dipole?  Looks dubious. I'd like to see the radiation resistance on that puppy.

'course there's also the biplane or butterfly antenna too. Two huge capacitor plates of aluminum with a couple of coils across them to resonate at the desired frequency. the plates were supposed to have the surface area of the length of wire of the dipole at resonant frequency ... or something 

[flintstone mop]

My take on the SLAB aerial is that it shines pretty well for 75M?

Fred

[K7NCR]

Some photos,,,,

[K7NCR]

more....

[K7NCR]

Last 2..
I got a nice piece of larch 2x10 for a window pass-thru for $.50 at Home Cheapo. Makes up for the $10.00 copper flashing for my ground panel! 
Norm K7NCR