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Can someone explain to me the matching device for a 5/8 vertical
- Thread starter cjruger
- Start date
The matching device can be made of almost anything. It can be aluminum or copper tubing, flat stock, etc. Use a 6' piece.
This site may help.
Fabricating CB antennas - Ham Radio Library
This site may help.
Fabricating CB antennas - Ham Radio Library
I want to attempt to build one but dont understand the wiring yet. Thanks for the links ill check them out
Ok, i dont understand something, i have read this antenna does not need ground plane wires and then i read it does. I want a 5/8 vertical end fed. Do i need ground plane or not? I thiught all i needed is a Matching device? That second link looked to be a 5/8 ground plane antenna.
Ok, i dont understand something, i have read this antenna does not need ground plane wires and then i read it does. I want a 5/8 vertical end fed. Do i need ground plane or not? I thiught all i needed is a Matching device? That second link looked to be a 5/8 ground plane antenna.
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Some have made 5/8 antennas without a GP, such as the Imax 2000. I personally believe all vertical end fed antennas need a set of GP to optimize performance. I have made a 1/2 wave end fed with and without GP radials, so I know it can be done, but whether it ought to be or not is where the line of discussion is drawn.
It is the studied opinion of many that those antennas that do not have a counterpoise/GP will tend to use the feedline in its place.
As for the matching device:
The bottom of the coil goes to the GP radials and the shield of your feedline coax.
The top of the coil goes to the vertical radiator and the center conductor of the coax taps the coil (red wire) at the proper point to achieve a match.
It is the same whether you choose to use a ring in similar fashion as the Maco V58.
There are other matching systems, but I chose the coil most often for its ease.
Here is a ring match:
It is the studied opinion of many that those antennas that do not have a counterpoise/GP will tend to use the feedline in its place.
As for the matching device:
The bottom of the coil goes to the GP radials and the shield of your feedline coax.
The top of the coil goes to the vertical radiator and the center conductor of the coax taps the coil (red wire) at the proper point to achieve a match.
It is the same whether you choose to use a ring in similar fashion as the Maco V58.
There are other matching systems, but I chose the coil most often for its ease.
Here is a ring match:
So it appears that the radiating element and the ground plane radials are attached to each other via the matching device? This is where i have been confused because i have been using a horizontal dipole, where the 2 halves can not be joined at all, i think i got it now and found a tonnof info at this link
http://www.cvarc.org/tech/antenna_myths/antenna_myths.pdf
http://www.cvarc.org/tech/antenna_myths/antenna_myths.pdf
I know your not going to understand this but it's worth a try.
A 5/8 wave length element has an 'excess' of capacitive reactance to the ground around it.
With this situation the matching section counters 'with' inductive reactance to canel it out.
When the proper setting is found for 50 ohm transmission line the SWR is can be near 1 to 1.
As for radials, you have to understand the radiating element is only 1/2 of a complete antenna.
You need radials to be proper and complete.
Those designs that use a metal stake in the ground and get a match to this are waisting efficieny by driving RF current through lossy soil instead of using wire or tubing radials beside the issues of common mode power coming back on the feedline.
The use of radials all but isolate common mode from the transmission line in most cases..
It's like trying the feed power into one half of a dipole. It won't match.
You need both halves.
A vertical is the same as a Dipole with one element vertical and one horizontal
(the radials).
If your confused about one vertical element and 4 radials, it makes little difference how many radials after about 6 are used and it make little differene if mutiple vertical elements are use if there are spread out enough from the feed point.
In fact it has an advantage of making the antenna tune a lower SWR over a wider bandwidth.
The term counter poise is not a good term to use in antenna theroy but means the same as radials.
Good luck.
A 5/8 wave length element has an 'excess' of capacitive reactance to the ground around it.
With this situation the matching section counters 'with' inductive reactance to canel it out.
When the proper setting is found for 50 ohm transmission line the SWR is can be near 1 to 1.
As for radials, you have to understand the radiating element is only 1/2 of a complete antenna.
You need radials to be proper and complete.
Those designs that use a metal stake in the ground and get a match to this are waisting efficieny by driving RF current through lossy soil instead of using wire or tubing radials beside the issues of common mode power coming back on the feedline.
The use of radials all but isolate common mode from the transmission line in most cases..
It's like trying the feed power into one half of a dipole. It won't match.
You need both halves.
A vertical is the same as a Dipole with one element vertical and one horizontal
(the radials).
If your confused about one vertical element and 4 radials, it makes little difference how many radials after about 6 are used and it make little differene if mutiple vertical elements are use if there are spread out enough from the feed point.
In fact it has an advantage of making the antenna tune a lower SWR over a wider bandwidth.
The term counter poise is not a good term to use in antenna theroy but means the same as radials.
Good luck.
I rebuilt my P500 last year using all new parts from MFJ. Less then thirty bucks including freight. Search this site for info. I'll post the number and part number this weekend if someone else doesn't.
Take your time with it! Do it right and your be glad you did. My antenna is one of the best ground planes in town.
Take and share pics!
Take your time with it! Do it right and your be glad you did. My antenna is one of the best ground planes in town.
Take and share pics!
The wiring is pretty easy. My biggest concern was that it didn't seem "right". I am used to typical AC and DC current principles and not RF. Here is the matching coil I built for my ground plane antenna.
I used a 6 ft piece of aluminum flat stock that is about 1 in wide and 1/8 in thick. It can be foud at your hardware store. I used my hot water tank to bend it into a semi circle. I left enough room to bend the ends in for mounting to the antenna system. One end will attach to the vertical radiator, the other end will attach to the ground plane/mast clamp. I took the center conductor of coax and soldered one end to the center pin of the SO239 connector. The other end was soldered to my slide clamp (for making the actual adjustment on the coil)
Radials and counterpoise are similar but different. A counterpoise is a substitution of radials but they have no relation to wavelength of the antenna and are not as effective.
Ok, as an aside, my use of the term "counterpoise" in the above post has prompted some comments, so I will do us the service, or disservice, as some may see it, of opening a thread to thrash this out.
Go to:
The truth and nothing but the truth - Counterpoise
Go to:
The truth and nothing but the truth - Counterpoise