The AM Forum

This weekend I shot a couple ropes way up in the top of two trees at the new QTH. They are up around 70 feet and 125 feet apart. Now to decide how to make 160 meters work. 1 hang vertical off the ends 2 fold it back on itself like Frank AHE does. 3 pull ends out lile a big triangle sloping to the side. 4. feed as a Tee.
Feed point is up around 60 feet to the basement window.

Where is the ideal feed location? Near one tree or the other or near the middle?

Mike

Middle of 125 foot run or Tree at the high end of the lot.  Yard is only 60 feet wide so VEE would be too tight. I have a 40 foot tree across the yard in the middle so could swing the ends over to it. Top of the lot have another 60 footer on other corner about 50 feet from end point tree.
I might even consider an inverted L on the other side of yard but would be only about 45 feet away from dipole.

Frank,

In the beginning...

I will start off the fun with a real old buzzard design that will produce big signals like they had in 1910. With proper ground radials, this will produce embarrassing amounts of antenna current.

Do the XYL and Neighbors have a vote?

Mike WU2D

boy, Frank, I would just love to have the luxury of a 120' flat top!!
I'd be like the proverbial pig in szht!!

Steve, the Huzman has an interesting setup for a 120' flattop that plays well on 160. He hangs a piece ov ladda line down vertically on each end to add some linear loading length. I think he has info on it ova on the am window somewhere.

                                                   The Slab Bacon

Mike

Looks like my 136 kHz transmitting antenna...

http://www.w1vd.com/XNStxantenna.html (http://www.w1vd.com/XNStxantenna.html)

Frank

Might make a good antenna especially since your close to the water.

Jay

I feed my 120' open wire fed flat top (center fed) with a K1JJ style tuner.  I used a silver plated edgewound coil out of a BC xmitter and the link is 1/2" wide by 1/4" thick copper STRAP.  Vacuum Variable capacitor.  I hafta tap WAY down on the coil to get it to resonate but it works pretty well all things considered.  The circulating current's gotta be pretty hefty but using the GPT-750 the coil gets barely warm to the touch after an old buzzard. 

Mike,
Someday I'll have a spark rig to go with Jay's antenna configuration.
I was lucky to get off two great shots with the bow. I had to stand under the primary wires at one end to get a bead on the branch I wanted. The lot high side is only low voltage so I didn't worry.
Yup know Huz configuration. I guess I will have to put something up and see how it plays. Looks like a Need about 60 feet of feed line and have a 250 foot spool of #8. I have a couple nice matched variable inductors that are 12 uh so should work good on 75 and maybe low Z on 160. They came out of a mil TX that ran 3 KW.
I'm not worried about the higher bands right now because I could fit a 40 meter dipole across the top of the lot and be away from the larger antenna.  fc
My neighbor was watching me but was afraid to ask....XYL told his XYL I was putting up an 80 foot tower a few years ago so he must be thinking the crazy man next door is moving his toys in.  fc

John,
I'm leaning to your configuration as a first cut. Cut the wire in half and make a 60 foot open wire line with 120 foot dipole. Would you please give me the size of your inductor so I can determine the inductance. Also do you have any idea of how much C it takes and you the primary side so I don't have to reinvent your wheel. I might drop 20 or 30 feet vertical but want to stay above the roof of the house peak.
tnx
PS this one day off per weekend has a nice ring to it now that I'm almost done with the sheetrock.

Inductor is about 3" diameter by 6", 22 turns.  IIRC it's about 30-40 uH but it resonates WAY down on the taps - both taps towards the middle with only a couple turns between them.  The cap is a 500 pF vacuum variable but it too is right at the end of its trvel.... I can get to 1870 but no lower.

I forgot to mention my dipole is in a fan configuration (2 wires each leg fanning out from the center, and connected at the center).  For this service (160 on a 75M antenna) the two wires in parallel on each leg probably help a bit due to the low impedance.

I think that should be added to the lyrics of:

I walk forty-seven miles of barbed wire, I got a cobra snake for a necktie
I got a brand new house on the road side, and it's made out of rattlesnake hide
I got a brand new chimney put on top, and it's made out of human skull
Come on take a little walk with me child, tell me who do you love?

 ;D

ham to the bone???

John,
TNX for the information. The trees are big enough to do a fan configuration and both ropes are on one side of each tree. I knew you had a fan and had that in the back of my mind. I have a pair of 12 uh variable inductors that are pretty heavy. I could do another balanced balanced tuner. I also have another 30 foot hunk of RG393 for a balun and a choice of large bread slicers or vv caps.
I would think a fan would lower the Q and help support the center.
Most people I talk so far to say don't do more than 30 feet vertical. 

Frank

The fan sounds like a good idea. You can always tie the feeder together and use it as a vertical. A good sized fan will provide 10 - 15 pF per meter of top loading. Looks buzzardly as well...

 

tell me WHOOOOOOOOOOO do you love  ;D

XYL doesn't let me bring pets home

How about food items?? I nice big pot ov rattlesnake chili would sure hit the spot!! 8) 8)

I can fan out the ends up to 40 feet. John have you tried connecting the ends. BTW My inductors are 12 turns each and I think 3 inch ID.
Strap is not 1/2 inch I think more like 3/8.
My tuner in Enfield has a pair of 22uH but the antenna is full size with about 70 feet of open wire line so Z is a lot higher.


WHO DO YOU STRAP?

I walk 47 miles of feedline, use a 4x1 for a neck tie.
I got a brand new shack by the roadside and its made of black wrinkle steel.
Its got little chimney up on top made from an 833.
C'mon take a walk with me now, tell me WHO DO YOU STRAP!!

How about a 1/4 wl inverted L?

I would guess that might give you the best all around (local & DX) signal with the your real estate restrictions on 160.

Of course you'll have to do the radial thing.

Terry
W8EJO

No, I haven't Frank, that would be an interesting thing to try to see what the difference (if any) is.

I suspect the feedline length is gonna make quite a bit of difference.  In my case my tuner happens to be at a very high current/low impedance point hence the very low taps on the coil.

Terry,
I could do an inverted L easily and have a good ground without radials. Low side of the lot is 5 feet above water under one of the support trees. A balanced antenna on the higher bands is what I am shooting for and could drive it as a TEE om 160 if I had to. Just outside the basement window I have a good connection to ground that runs down the sewer line trench into water at the bottom of the lot. It is also tied into the water and a loop around the footings.
Balanced antennas seem to be less of an RFI problem but with a second tuner it would be easy to change.
John I will also have about 60 feet of feed line #8 spaced 4 inches so Z should be low.
 

OM,

The August 2005 QST has a design that looks like a perfect fit: it's intended for a 120' distance and offer a 50 ohm load.

HTH.

73, Bill

what does it look like? I only get QEX
I don't care if it is 50 ohms.

I got 47 miles of copper wire, in a phased array for end-fire...

I got 22 pills on a heat sink .....who do you strap
 

Sounds like a tee is your best bet. At 70' height, on 160 it should behave nearly identical to an L giving you a decent vertical plane pattern. I remember my 450' doublet @  60' was pretty bad for anything beyond 300-400 miles at night on 160. When I went to a Inv. L it was an enormous improvement even though it only had eight 1/4 wave radials. The L was also a better all band antenna IMO. 

There are several possible designs in the article, but the one that caught my eye looks like this:

                 **************************************     (Horizontal 120' section 60 feet above ground)
                  *                           120'                          *
                     * 23.5'                                          *
                        *                              74.9'      *
                     *     *                                    *
                 *            * 51.4'                   *
            *                    *                  *
       *                            *          *
 (coax)              (Ends six feet above ground, separated by twelve feet)


Aug 2005 QST   p33 figure 3      Short Dipoles for 160 Meters   Koontz, Floyd, WA2WVL



The author recommends a balun at the feedpoint, and estimates -1 dbi gain and 50.1 +j4 ohms impedance.

HTH.

Bill, W1AC, who has found out that you have to turn off spellcheck when doing ASCII art.

TNX,
Bob W1RKW sent me a copy. I know Floyd so I sent him an email. He is retired from Harris and quite sharp. Sounds like a vertical drop is doable  in my case.
I did a bunch of surfing and under 200 feet long you need  a heavy duty tuner and feed system to reduce losses. The antenna efficiency didn't change a lot if you can get it to take power. gfz

Has anyone here succeeded in getting good results from a half sloper on 160? I've been reading the comments here, gotta get something up on 160 for my BC XMITTER. I ran one off my 30 foot tower, the top angle was less than 45 deg, and after shortening the length, it looked like 30 ohms + 0 at the tower top feed point on 1900 KHz, so I built a toroidal autotransformer (for low power testing) to match it to 50 ohm cable. Could not get good match at the bottom of the tower feed point. Somewhere I read that the vertical leg of the ground to the sloper (tower) is radiating too, and that it is included inside the antenna. In other words, measuring the match up at the top is like sticking an impedance meter in the midst of driven element of a yagi, and that the entire structure needs to be measured as a whole. I have the tower base grounded with refrigerator tubing radials in 4 locations.

I have read (here) that vertical component of radiation is important on 160, although I am not sure if that is for the ground wave local field component or for bouncing off the ionosphere. MW radio stations seem to have pretty strong skywave signals at night, and they are vertically driven.

Anyway, am following this discussion with interest. I do have possibly 220 feet from corner to corner of my 1 3/4 acre lot, but 7200 volt AC line is perpendicular to this bearing, at the far end.  My present HF dipoles are hanging from about 160-170 feet away to my tower, and i have underground RG8 running to the center point.

John,
       My findings over the years on horiz vs vert antenners has been that vertical ants have a low take off angle. This gives good true ground wave, crappy short skip, but good long haul skip. Flat tops on the other hand have terrible ground wave characteristics, but are good for both long and short skip, maybe favoring the shorter skip a little depending on the height of the ant. I guess it all depends on the type of operating you do most.

Somebody gave me opne of those Alpha-Delta coil loaded slopers that hang off of the side of your tower. They use the tower as one side of a somewhat inverted "V". It actually transmitted pretty well. But............
I had RFI problems out the wazoo. It was so bad that I stopped using it after the first night and went back to the short flat top. I have always had better luck with balanced antenners and balanced feedlines. My problem here is that I only have about 70' of horizontal run to put up a horizontal antenner.
                                                        The Slab Bacon

Yea, I kind of wondered about half slopers, as the tower becomes part of the radiator, yet it is 'ground' for the shield on the coax. Makes me remember that coax should work with all the RF flowing inside the shield and on the center conductor. With a high power transmitter, this could prove troublesome too, on 160.

Email from Floyd suggests hanging the ends vertical will give higher gain than swinging them back on themselves. I think that will fit in my case but one end will be fairly close to the house.

Cebik seems to like the center fed inverted L. Interesting an old  Signal corps. guy I knew suggested it years ago. He is SK now but his fist was very clean and got me to 35 WPM. He designed my Quad years ago that worked great for 19 years.

Frank

A quick Eznec simulation on your 120' flat top at 60':

3.9 MHz

NO dangles     78 - j29     
10' dangles   120 + j267   
20' dangles   183 + j607   
30' dangles   296 + j1053   

1.9 Mhz

NO dangles    6.8 - j1282
10' dangles    9.1 - j1025
20' dangles   11.6 - j807
30' dangles   14.4 - j615

Angle of the dangle appeared to be better straight down rather than folded back on itself. Gain varied only a few tenths with or without dangles.


 

Jay,
TNX fer the dope OM. How about one more, try throwing in 60 foot dangles

Also looking at about 65 feet of feed line #8 spaced 4 inches.
I could go to 6 inch spacing if it matters. Looks like the dangles make it easier to match on 160.

Frank

60' dangles would be touching ground so went with 50'...

3.9 MHz

50' dangle     1609 + j3159


1.9 MHz

50' dangle     22.7 - j271

With the 50' dangles gain is down over 1 dB. Looks like 25' might make a good compromise. Don't think 4 or 6 inch spacing will make much difference. Thick feeder wire is certainly in order for 160 - especially if you're pushing 20 pills.

thanks Jay. I think I can get close to 60 feet vertical and still be above ground by 10 feet. I think the trick is to get the resistive up higher. Yup I may lose 1 dB of gain but may also lose 2 dB of loss.  The transmission line z of 6 inch of #8 and 4 inch of #8 is about 60 ohms so agree.

Frank,

Can you send over enough details via E-mail so I can make a drawing of what you are planning on doing for everybody to see?

Mike WU2D

Mike it is pretty simple I'm on the side of a hill facing west over a salt marsh. The low side I have a rope in a big oak up about 65 feet. The land slopes up about 30 feet and the lot is 175 feet deep. I have another oak on the high side with a rope up about 75 feet. The distance between the two trees is 120 to 130 feet. The House is on the high side so the feed line comes down next to a basement window almost directly below the center. The lot is only 60 feet wide.
I'm looking at a 120 foot or so dipole with vertical ends. I'm told swinging the ends across the lot to a 40 foot tree on the other side  would reduce gain. This tree is about 1/2 way up the hill but on the south side while the antenna is on the north side. The yard is too small for a sloping V to the west. or a sloping V going up hill to the east. The bottom line is I will build a 250 foot dipole and maybe move it around to see what works best.
Maybe I'll grow nads and ask my neighbor if I can use his tree which would give me a V sloping SW. I figured I would put it up first and let the copper turn brown. They asked about all the rope in the air this past Saturday.
There is one other oak at the south east corner. I'm considering a lazy H facing east west across the east side for 40 and above so a dipole across the north side would be ok and vertical ends would increase the input Z so I could get on 160 without a ton of loss

Anybody ever play with a 1/2 wave center fed inverted L.
I think I can sneak one up on top of my lot and feed it with open wire line for a low angle antenna 80 - 10 m.