Collinear, 1/4 wave GP, or J Pole (arrow)

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SpugEddy

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I've been reading a lot about homebrew antennas
in the past 3 days.
What I've learned:
1/4 wave ground plane = easiest to build
Arrow type J Pole = hardest to build
Coaxial Collinear = kind of sloppy to build. Many hams now saying they do NOT work

Here are the questions I have now:
1/4 wave ground plane - Do I get any gain with this antenna?
J Pole - Again, what kind of gain can I expect? How can I adjust antenna for best SWR?
Coaxial Collinear - Can I use RG59 coax and expect good results? Is 75ohm coax a no-no?
Top element - Connected to center conductor only or both center conductor and shield?
Bottom element - All plans point to 5/16" aluminum tube. Can I use 3/8" copper tube?
Will changing the size of the tube change the whole formula?
And, once again, what is the theoretical gain of this antenna?

This is a DIY project for an antenna in the UHF band.
Just something to throw on your brain's backburner:
I have an Ed Fong antenna and I am not happy with it at all.
I have a Motorola CDM 1550, LMR-400 coax, connect to Ed Fong's
antenna and I cannot reach a station 5-7 miles away. I connect
my Baofeng BF-F9 handheld to a 1/4 wave ground plane, RG-58 (about 7') and I can
hit the very same station. I have a better SWR, less reflected signal,
and better forward signal using the $30 radio and the $3 antenna.

Ed Fong antenna is approx. 20' off the ground mounted on a mast and grounded.
DIY 1/4 wave hanging on a nail in my shack about 6' off the ground.
 

AK9R

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1/4 wave ground plane - Do I get any gain with this antenna?
Referenced to a dipole, no.

J Pole - Again, what kind of gain can I expect? How can I adjust antenna for best SWR?
Referenced to a dipole, no. Typically, J-poles are tuned by adjusting the height of the feedpoint relative to the shorting bar.

Coaxial Collinear - Can I use RG59 coax and expect good results? Is 75ohm coax a no-no?
You can use 75 ohm coax with a transmitter expecting a 50 ohm load, but the transmitter will see no better than 1:1.5 SWR no matter how well you tune the antenna.

Ed Fong antenna is approx. 20' off the ground mounted on a mast and grounded.
Is the mast metal? If so, it is de-tuning the Ed Fong J-pole. J-poles are an end-fed half-wave fed with a quarter-wave transformer (the dual-element portion of the J-pole at the bottom of the antenna). If anything metallic gets in the field of the transformer, it upsets the action of the transformer.
 

nd5y

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I have an Ed Fong antenna and I am not happy with it at all.
I have a Motorola CDM 1550, LMR-400 coax, connect to Ed Fong's
antenna and I cannot reach a station 5-7 miles away. I connect
my Baofeng BF-F9 handheld to a 1/4 wave ground plane, RG-58 (about 7') and I can
hit the very same station. I have a better SWR, less reflected signal,
and better forward signal using the $30 radio and the $3 antenna.
You found out the hard way that j-poles suck.
 

SpugEddy

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W9BU... Yes the antenna mast is actually a 20' pc of
fencepost toprail. 1 1/4". It is secured to the back of my shack
by 2 pieces of Unistrut. 1 at the top of the shack (12') the other
at the bottom (about 2-3' off the ground)

I really thought these Arrow Open Stub J Poles were really a good
antenna. So much for that theory. So, it's either buy some lower end
commercial antenna or find a better antenna to build. I suspect Yagi
is going to be what most hammers are going to suggest. But if everything
references to a dipole, then is that a better project. I have a dual band
dipole that I made a while ago but my design falls a little short for actually
mounting it up high. (I need to re-engineer the mounting design)
Putting out some money for an antenna is not a problem for me.
I just seem to get a lot of satisfaction out of making something myself
and having it work. I love the challenge and it also keeps me out of my
wife's hair.
 

lmrtek

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build a 3 element quad

they are VERY easy to build and provide great performance
 

TheSpaceMann

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I'm surprised that you had bad luck with Ed Fong's antennas. If you look at their reviews on eHam.net Home - Amateur Radio (Ham Radio) Community Site , you'll see that many hams have had good results using them. Save yourself a lot of time and money, and just build yourself a ground plane! If you want to go the beam route, I suggest the small ELK 2m/440 log periodic beam. I've been able to hit repeaters well over 50 miles away with it, even when used indoors!
 

dsalomon

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One more difference between 1/4 wave, j-pole and slim jim antennas is the takeoff angle. Typical takeoff angles are:

1/4 wave antenna: 25'
j-pole: 20'
slim jim: 8'

Consider your location vs the repeater location. If you're in a valley, higher takeoff angle might get better results. On flatter ground, a slim jim will perform much better than either of the other two because more of the signal is radiated towards the antenna vs up in the air.

Here's an interesting graphi from a guy who did a comparison at 30' from the three antenna types: http://forums.qrz.com/index.php?attachments/antennatest-jpg.323528/. It clearly shows the slim jim as the best performer.

I've used all three types from my location and stayed with the slim jim for noticeably best performance. They are also easier to build than a j-pole. N9TAX sells a 2/440 slim jim made (Google him) of ladder line that is very inexpensive and holds up extremely well. I've had mine hung from a tree branch at 70' for over a year. It works great, outperforming every other 2/440 base antenna I've tried. It's also low profile and inexpensive to replace if anything goes wrong.

73 - David, AG4F
 

AK9R

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Yes the antenna mast is actually a 20' pc of fencepost toprail.
If your J-pole is laying along that "mast", then that's why your J-pole doesn't work.

Some hams suspend their J-poles inside PVC plumbing pipe (use white PVC, not gray, as the gray PVC may have some carbon black in it for coloring which tends to make the pipe a bit conductive) and then attach the bottom of the pipe to the top of their mast. This keeps the transformer portion of the J-pole away from the metal mast.
 

jonwienke

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If your J-pole is laying along that "mast", then that's why your J-pole doesn't work.

Some hams suspend their J-poles inside PVC plumbing pipe (use white PVC, not gray, as the gray PVC may have some carbon black in it for coloring which tends to make the pipe a bit conductive) and then attach the bottom of the pipe to the top of their mast. This keeps the transformer portion of the J-pole away from the metal mast.
+1 on this.

Also, Ed Fong recommends the 200PSI PVC because it has thinner walls and affects RF propagation less than the standard-thickness pipe.
 

jim202

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You found out the hard way that j-poles suck.
I don't understand why your saying that a J Pole antenna doesn't work.

They are a very good antenna if built correctly. They may take a little playing around to get the SWR down low, but once you get it tuned, they work well.

There are a number of postings on the Internet on how to construct these antennas and how to tune them. There are some very detailed information on constructing them.

If your having a problem with a J Pole, then you have done something very obviously wrong in how you put it together and tuned it.

Don't bad mouth a J Pole antenna just because you may have an issue with it. Pull out the instructions and your SWR meter and find out what you did wrong.

A J Pole antenna will walk circles around a simple ground plane antenna. It will walk circles around a dipole antenna. Just remember this is a vertical polarized antenna generally used for FM and not made to use on SSB that is normally a horizontal polarized mode of communications.
 

SpugEddy

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W9BU.. Yes the antenna is inside of the recommended pipe.
I followed the instructions to the letter. It is strapped to the mast
at the bottom 4" of the antenna.

DSALOMON may have something. Where I live I am at a very low elevation.
I think I am like 30+ feet. The elevation of the station I can't
reach is approx. 160'+ then 100'+ antenna height.

Jim202.. What I'm saying is: My antenna does work but it works poorly.
I did not build this antenna. I actually purchased it. I indicated the frequencies
that I would be using the antenna and I was told that it was tuned to those freqs.
I am NOT "bad mouthing" J Pole antennas nor Ed Fong's design or his antennas.
When something works poorly (as this) I can't sugarcoat the facts and the fact is
that it performs poorly in my application. The good reviews and the concept of students building the
antennas and using the money for further education was the very reason for my
buying this antenna. But now I search for other options that may yield better
results and performance.
 

jonwienke

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Post pics of your install, including how the antenna is grounded. I have a Fong J-pole, and while it may not be the absolute best out there, it is a decent antenna that should perform better than what you're describing.
 

KC4RAF

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The J-Pole is a good antenna.

I built the J-Pole antenna back in 12/2015 and am very satisfied with it. I've hit repeaters over 25 air miles from my base with 5 watts without any problems. Going simplex on the same wattage at over 35 air miles. All responses were positive.
One amateur who lives over in Orlando was surprised that the J-Pole worked as well as mine. He said the one he experimented with was junk. After talking with him, we discovered that he was hanging it along side his tower about 3 feet out! Also his connections to the feed points lacked good contact. After he made the feed points right and hung the antenna from a tree for testing, he received good reports and was able to reach out many more miles. Now he's a believer in the J-Pole.
Here's a picture of mine that I built (954):

edit: sorry guys, the jpg won't upload at this moment.......
 

Rred

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"I just seem to get a lot of satisfaction out of making something myself
and having it work. I love the challenge "

ARRL Antenna Book, even a 2-3 year old edition, will answer many of the questions AND give you guidance into making your own antennas, complete with the issues of how to tune and what is more difficult to build. Coaxial Colinear's certainly do work--but there can be some confusion over dimensions and cutting them correctly will require more attention to detail than something like a 1/4 wave whip which can simply be pruned to tune it.

FWIW.
 

jonwienke

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What exactly did you connect the ground wire to inside the PVC? You may have ruined the antenna depending on exactly where you connected the ground, and how.
 

jonwienke

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In particular, if you connected the ground wire anywhere above the ferrite choke on the coax stub at the bottom of the antenna, you've grounded an active radiating part of the antenna, and SWR and performance will be crap. The correct grounding point is the shell of the SO-239 connector.
 

SpugEddy

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OK. So I'm safe on the first part of your post.
As far as the shell of the coax. I'm not 100% sure.
Hard to say because I'd have to take off all of the
tape to get to the shield to meter it.
I know I am earth grounded on the shield at the
radio end. And since the shields are common on
both ends, electronically I am grounded. Just not
directly from the antenna end shield to earth.
 
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