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How do i make a make a matching device for 5/8 antenna?

C

cjruger

Active Member
Aug 13, 2012
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I tried a coil of copper wire between the shield and center conductor, no matter where i tapped it the swr did not chang and was almost in the red. I read all the other post in the other thread and cant seem to figure out exactly what i need. I dont have ground radials, its just a wire hanging from tree to about 5 ' above ground. If i can get it to work i will put it up higher.
 
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cjruger said:
I tried a coil of copper wire between the shield and center conductor, no matter where i tapped it the swr did not chang and was almost in the red. I read all the other post in the other thread and cant seem to figure out exactly what i need. I dont have ground radials, its just a wire hanging from tree to about 5 ' above ground. If i can get it to work i will put it up higher.
Click to expand...
Hi, you need to tell us a little about your configuration and how you have put it together.
For example have you got a SO239 where your coax is fed into via a PLplug, have you got a ground plate where the SO239 is fastened to. How is the copper wire which is your driven element (fed by the center wire of the coax) suspended and what is the relationship of your driven element to the rest of the antenna?
Without this information we will struggle to see the electrical property of your antenna.
 
Agree with Nav's comments, But just on the basis of what you posted, your antenna will never match if it lacks radials. As far as what I can tell from your post, If your vertical wire is in the neighborhood of 22' - 23' long, and your coil has its top connected to the wire vertical, with the braid to the bottom as in my illustration, add some ~9' radials to the bottom of the coil, and tap the coil with the center conductor to get a tune.

5eighths.jpg
 
I dont have room for radials that is the problem. Im not sure about where the center cond. attaches to coil. I made a little fixture that has aa male pl259. The radiating element basicly plugs right in to the other end of the male pl259 and goes up. The coil bolted on the frame of tthe block the male pl259 is threaded in to( small about 1"x 1") then a wire, 1 end fastened to radiating element( about where it goes in to male pl259) the other end with gator clip to attach to coil at different spots. I thought i read this antenna could work without radials but maybe i misunder stood. I could try some short ones, how short can they be and work?

Here is the block, the radiating element fastens to a prong that plugs in and my coil attached to frame and went around radiating element. Its fastened to block of wood for temporary testing, thinkig of making alum plates like the pics in the build linked above. I have 4 tapped holes on lower corners for possible radial wires( where wire connector is hanging) just dont have the room to spread them out. Maybe i can figure out a way to try some

D1D0D4F1-544D-42E0-846C-97DEC9069D93-1500-00000281789BFEA7.jpg


Ill post a pick of the coil set up later when i get home
 
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cjruger said:
I tried a coil of copper wire between the shield and center conductor, no matter where i tapped it the swr did not chang and was almost in the red. I read all the other post in the other thread and cant seem to figure out exactly what i need. I dont have ground radials, its just a wire hanging from tree to about 5 ' above ground. If i can get it to work i will put it up higher.
Click to expand...


You really need some form of radials HOWEVER you have the coil wrong. The coil is in series with the feedline center connector and the antenna and the coil has a tap to ground (the coax shield) Both the overall number of turns as well as the tap point need to be adjusted for proper match. This why I prefer 1/4 waves (VERY easy to match) or 1/2 waves (harder than a 1/4 but still easier than messing with a 5/8 ).
 
Captain Kilowatt said:
You really need some form of radials HOWEVER you have the coil wrong. The coil is in series with the feedline center connector and the antenna and the coil has a tap to ground (the coax shield) Both the overall number of turns as well as the tap point need to be adjusted for proper match. This why I prefer 1/4 waves (VERY easy to match) or 1/2 waves (harder than a 1/4 but still easier than messing with a 5/8 ).
Click to expand...

Well now im completly confused, is that not what i had? The coil end is fastened to frame of block( braid) the gator clip on opposite end of coil goes to center conductor
 
Yes, and the opposite end of the coil goes to your wire vertical.

4521.jpg


The bottom end of the coil is fastened to the radials and the braid of the coax. The top end of the coil is fastened to the vertical radiator, in your case a wire. The center coax conductor is fastened to the long screw which is tapping the coil at the proper spot to get a match (low SWR). You must have radials. If you can not, then neither is a 1/4 wave an option as it needs them, too. The matching network for an end fed half wave is more complex than the 5/8 wave, in my experience.
If you want a vertical half wave without radials consider a dipole - two pieces of wire fed in the middle, one wire up, one down. Make sure your feed line (coax) is drawn straight away from the dipole without hanging down beside it.

See diagram:

coiltapped.jpg
 
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Thanks for the input, i may abandon the idea, i am currently using a half wave horizontal dipole on my roof, it works really well, just always trying to improve, i guess ill work on radials befor i go any further
 
here's another coil example .

IMG_0065.jpg


ground radials are cheap and easy .

BELOWANTENNA.jpg


just four 9 ft pieces of speaker wire with a X standoff made of two 10 ft pieces of i inch s40 PVC tubing cut in half and 1 inch 4-way . just attach them to the ground/shield of the connector .
 
cjruger said:
Well now im completly confused, is that not what i had? The coil end is fastened to frame of block( braid) the gator clip on opposite end of coil goes to center conductor
Click to expand...

From the way you described it it sounded as if you simply had a coil across the center and shield connections of the coax and no tap. Maybe you did but it did not sound like it. The pictures above do show the proper way to do it.
 

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