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Author Topic: What to do what to do  (Read 23466 times)
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WA1GFZ
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« Reply #25 on: August 01, 2007, 02:17:22 PM »

what does it look like? I only get QEX
I don't care if it is 50 ohms.
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W1GFH
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« Reply #26 on: August 01, 2007, 04:31:19 PM »

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!!

I got 47 miles of copper wire, in a phased array for end-fire...
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WA1GFZ
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« Reply #27 on: August 01, 2007, 04:52:29 PM »

I got 22 pills on a heat sink .....who do you strap
 
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W8EJO
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« Reply #28 on: August 01, 2007, 06:29:42 PM »

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.
 

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. 

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Terry, W8EJO

Freedom and liberty - extremist ideas since 1776.
W4EWH
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« Reply #29 on: August 01, 2007, 07:34:27 PM »

Quote
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.

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


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.
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WA1GFZ
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« Reply #30 on: August 01, 2007, 09:41:15 PM »

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
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John K5PRO
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« Reply #31 on: August 05, 2007, 11:49:22 AM »

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.
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The Slab Bacon
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« Reply #32 on: August 06, 2007, 12:21:10 PM »

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
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John K5PRO
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« Reply #33 on: August 06, 2007, 06:15:18 PM »

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.

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WA1GFZ
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« Reply #34 on: August 06, 2007, 10:28:57 PM »

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.
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W1VD
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« Reply #35 on: August 07, 2007, 03:22:12 PM »

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.


 
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'Tnx Fer the Dope OM'.
WA1GFZ
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« Reply #36 on: August 07, 2007, 03:42:00 PM »

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.
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W1VD
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« Reply #37 on: August 07, 2007, 05:00:21 PM »

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.
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'Tnx Fer the Dope OM'.
WA1GFZ
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« Reply #38 on: August 07, 2007, 10:07:52 PM »

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.
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WU2D
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CW is just a narrower version of AM


« Reply #39 on: August 08, 2007, 02:07:01 PM »

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
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WA1GFZ
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« Reply #40 on: August 08, 2007, 02:43:42 PM »

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
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WA1GFZ
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« Reply #41 on: August 14, 2007, 03:31:03 PM »

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. 
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