The AM Forum

I finally got this scanned in so I figgered I would post it for all to see and / or complain about. With all of the discussions lately about limited space antennas, this is what I have been using for some years now with great success. Many of you that have been to my qth have seen it, and many of you that have worked me have heard it, so I do know for a fact that it works quite well. If I can hear them, I can work them. And noone ever seems to have any trouble hearing me. I usually run QRO, but have also been heard running pissweak low power as well when condx warrants.

Mine is hung 35' off of the ground, and I have used it from 160m to 10m with pretty good results. It works very well on 75m and kicks ass on 40m. The 160m performance leaves a lot to be desired, but that is to be expected from a 60' long antenner. I have been using it on 75 for the main station anrenna for some years now.

Here are a few notes to consider.
1. since it is a non resonant antenna, none of the dimensions are real
critical.
2. Use BALANCED feeders only, something fairly heavy gage to handle heavy feedline currents. 14ga crappy brown stuff is the absolute minimum, if you are using it on 160, consider 12ga or heavier.
3. do everything you can to minimize I/R losses, this is critical to putting out a good signal.
4. USE A ROBUST TUNA, ONE CAPABLE OF MATCHING A VERY LOW IMPEDANCE LOAD AND HANDLING HEAVYFEEDLINE CURRENT! No MFJ junk or crappy ham grade stuff if you plan to run real power, you'll smoke it!! My tuna is a large HB single ended "T" type unit in a box the size of an R-390 and I use a large HB ferrite balun wound with #10 silver teflon wire and 4lbs of ferrite. Again do everything you can to minimize the I/R losses. Anything that is getting warm means you have power that is NOT getting to the antenna. Heat = loss!!

I hope this will help some of you that like me are space challenged to get on the air and have some fun!!

I kinw that there will be some nay-sayers out there that will swear it wont work well, but the proof of the pudding is in the eating, and i have been "eating" well for some time now. Say what you wish, I KNOW that it works!!

                                          The Slab Bacon

Bacon,

Please post a diagram of your tuner: I'd like to know more about it -

• Is the balun on the input side like the "ARRL Tuner", or on the output?
• Would a balanced design make a balun unnecessary?
• I assume you float the low side of the T network inside the box. What kind of clearance is needed?

Thanks!

Bill, W1AC
http://billhorne.com/ (http://billhorne.com/)

Bill,
     A balanced tuna would definately make the balun unnecessary.
However you would have to make the tuna capable of matching to a low-Z load, Basically a "step down transformer" if you would.

No, I dont float the bottom leg of the coil in the tuna as I run a very short run of coass to the balun. (About 6') to escape all of the metal in the storage closet behind the tuna. The tuna is just a simple "T"
series cap in, coil to ground, series cap out with wide spaced bread slicers and a large rollie duck from a broadcast transmitter.

You have seen the whole setup when you were here back in the spring. You even commented about the antenna.

                                               The Slab Bacon

I would also like construction details of the tuner. 

Someday I will try to get my HB 813 transmitter on the air an the matchbox won't cut it.

Thanks

Rich

If I get a chance I will sketch it out over the weekend. But I will have to bring it in to work next week to scan it in.

It is so simple that you really shouldnt need details. 2  400pf wide spaced breadslicers, and a large edge wound ribbon roller inductor in a big box. Your basic "T" type tuna. Or as Chris (W2JBL) calls it ----
the worlds largest MFJ tuner!! (I prefer a T type as it affords a very wide range of matching) the Balun is a 4:1 design right out of the ARRL handbook, just supersized and fed massive amounts of steroids. I did experiment with and wind a lot of different balun designs and then sweep them. I found that the 4:1 adds the least reactive component of its own to the mix, no matter what the operating impedance was.
1:1s were very impedance specific.

                                                The Slab Bacon

I'm going to use a link-coupled tuner, like Brent W1IA, so I think that will give me the choice of ratio I'll need.


Well, they say the memory is the second thing to go: I know you showed me the setup after Timonium, but I forgot.

I was assuming that you had the balun on the input side of the tuner, since the ARRL design puts it there, and that would (I think) require isolating the bottom of the "T" network from ground. It's good to know that a 4:1 design doesn't necessarily have to be on the input side of the tuner.

BTW, did anyone ever come up with an "official" name for your antenna? My brother and I were debating if it was a "crooked dipole", or a "divorced folded dipole", or possibly a "broken barrel dipole", but the definitions got more hazy as the afternoon wore on and the 807's warmed up.  ::)

73, Bill

No, we havent come up with a name for the ant, but.......................
since I built the tuna in a 19" rack mount box and had nowhere to put another rack cabinet, I cut a hole into the wall and racked the tuna into the wall. Henceforth it is now called "the hole in the wall tuner"

                                                            The Slab Bacon

Saw this ant in an old handbook....

Or at least in with the folded dipole, they mentioned leaving the center disconnected...to give the ability to use it on more than one band...

On the freq it's cut for the top "appears" shorted, and on higher freqs, it is open...
Something like that,,

That's what Frank is using, a 60 foot long folded dipole, with the top leg open and the bottom leg fed.

>snip<
 "Saw this ant in an old handbook...."

That is where I got the idea from!! Steve sent me a page scanned from a very old handbook some years back, and I said "what the hell, I'll try it". The rest iz history. There are many very good antenna ideas that have been forgotten about since the introduction of coass and rice boxes that wanted 50 ohm coass feeders. Over the years many people have come to shun antennas that had to have balanced feeders in favor of the easier to install coaxial cable designs.

But that is why they invented the tuna!! Sometimes you just gotta do what you gotta do!
always remember that a compromised antenner is still way, way better than none at all, and if you can find one that works well you can have your cake and eat it too!

                                                                               The Slab Bacon

You bet those old Handbooks have some good antenna ideas!  Back then, more people rolled their own antennas, rather than buying them.  So they had more antenna stuff in the handbooks.  A case in point - I got on 160 back in 1986 from of all places, an apartment!  I got the design for a shortened helical vertical (basically a rubber duck on steroids), from a 1972 Handbook.  It wasn't the greatest, but it got out with my FT-101B.  A few years later, it was no longer listed in the Handbook.

Slab, as for your antenna - it's almost like folded dipole, but I'd say it's closer to a dipole combining  both capacitive and linear (although not in the traditional sense of having the ends droop down) loading.

73,
Ellen - AF9J

I am using a short antenna when on 160M, it is 135 ft fed with #14 window balanced line.   I am using an MFJ 989C T tuner but I am using a hefty DX Engineering made-for-tuner type balun on the output side, not the crappy one in the tuner.   These things work much better than the one in the tuner both for balance on the low bands and power handling capability.   I have no connection or interest in DX Engineering but using one made for 10KW continuous power makes this configuration usable and effective.

Are the top & bottom wires electrically connected? I'm trying to model it with 4nec2.

Terry
W8EJO

Good Afternoon,

 I can attest to the vertical helix, built one here for 160 some time ago using schedule 40 plastic pipe with a 70 foot resonator off the top, used on ssb phone works great...then i turned it into one of my receiving antennas it does a great job for vertical receiving, i like it alot....

jack ka3zlr

There is a "left wire" and a "right wire".

It's a folded dipole, that is "snipped" in the middle, above the feedpoint.

OK thanks. That wasn't self evident from the drawing.

Vertical & Horizontal patterns @ 3.8mhz.

Yup and on 160 it is all high angle so all you need to do is match the very low Z.

To really tell what is going on, you need to do pattern comparisons with a dipole at the same height. I ran those sims. See image below.

In the sim of the AHE antenna, at 3.8 MHz, the feedpoint impedance is Real(Z) = 11.3874, Imag(Z)  = -305.197. Using W9CF's feedline calculator, at the end of 70 feet of 450 Ohm Window line (this is my guess on the length in use at AHE radio) the Z is 107.34 +j1124.1. Loss in the feedline is 2.76 dB. The 107 Ohms resistive isn't bad, but there sure is a ton of inductive reactance for the tuner to deal with!

So, from the antenna plot, we see that the AHE antenna is down about 1 dB compared to a dipole, when there is NO feed loss. A dipole cut for 3.8 MHz and fed with 70 feet of RG8 would have feedline loss of 0.27 dB. Adding in the 2.76 dB of feedline loss to the AHE system, it would appear the Frank's antenna is about 3.5 dB down from a dipole. This doesn't include tuner loss. Who knows what the loss in Frank's tuner is. Can't be much based on his signal. But for giggles, lets do some simulations.

Using W9CF's tuner simulator and plugging in the Z numbers calculated at the end of 70 feet of feedline, tuner loss is only 0.3 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 the coil a Q of 100. There's likely a little more loss in the balun. But looking at the size of the one Frank made, it's probably small. So, worst case, Frank's antenna is about 4 dB down from a dipole. Not bad considering the size!

I've always thought Frank's set up was within 3dB or so of a full sized dipole. The cool thing is, according to the transmission line sim, almost 2dB could be gained by using 600 Ohm open wire line!

I think the orange Super Bee parked underneath it gives Frank an extra couple a dB or so   ;D

thatz right!! The 440 sixpack in the super bee gives it that real "high performance" signal!! ;D ;D

All kidding aside, thats why I posted it. I know that it works well. All that have ever worked me know that it works well. Compromise antenna or not, it might help a few others that are "space challenged" like myself get on the air!

Steve,
       believe it or not I have been planning some homebrew feeders but just havent had the time lately to do it. Ifin it aint broke dont fix it! I just cant seem to find that one missing part that I need for the hb feeders, you know the round tuit ;)

                                                      The Slab Bacon

yea, but I'm on the air ;D  8)

And with straight pipes, it's loud too!

It's talkers versus doers, Frank.

No, Mopar only!

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

Lotz of tiresmoke is a good "burnt offering" to the gods of RF!! ;) 8)

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

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

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.

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.

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.

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

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.

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.

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)

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

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.

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

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.

I would be very interested in your results.

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

anyone ever try one of these?

(http://www.tak-tenna.com/EA5AMM.jpg)

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  ::)

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

Fred

Some photos,,,,

more....

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