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Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

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  #21 (permalink)  
Old 05-24-2017, 12:20 PM
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Quote:
Originally Posted by AI6VX View Post
I thought Ed's antennas were also known as a Slim Jim ?


No, they're j-poles. http://edsantennas.weebly.com/about.html


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  #22 (permalink)  
Old 05-24-2017, 12:24 PM
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I can vouch for the Ed Fong dual band antennas. The best part of it all is that it's shipped in a small sandwich bag. All you need to do is buy the recommended PVC pipe grade (in the instructions) at Lowe's or Home Depot for a few bucks. Slide it in and it's done.
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Old 05-24-2017, 12:33 PM
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Originally Posted by MaximusTheGreat View Post
I can vouch for the Ed Fong dual band antennas. The best part of it all is that it's shipped in a small sandwich bag. All you need to do is buy the recommended PVC pipe grade (in the instructions) at Lowe's or Home Depot for a few bucks. Slide it in and it's done.
I have 3 of them: a dual-band base, a tri-band base, and a roll-up for the go kit. If you live in the Bay Area, you can pick up pre-assembled units at Ed's house if you contact him to arrange it. I'm sure Ed gives fair warning, but if you assemble it yourself, use the recommended schedule PVC pipe or you will move the center frequency of your antenna. The tri-band doesn't ship in a baggie because of the careful tolerances of the 1.2m coiled radiator.

As far as a recommendation? They just work, and have SWR of <1.1 on all 3 bands of my tri-band.
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Old 05-24-2017, 2:49 PM
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Quote:
Originally Posted by plughie View Post
I have 3 of them: a dual-band base, a tri-band base, and a roll-up for the go kit. If you live in the Bay Area, you can pick up pre-assembled units at Ed's house if you contact him to arrange it. I'm sure Ed gives fair warning, but if you assemble it yourself, use the recommended schedule PVC pipe or you will move the center frequency of your antenna. The tri-band doesn't ship in a baggie because of the careful tolerances of the 1.2m coiled radiator.

As far as a recommendation? They just work, and have SWR of <1.1 on all 3 bands of my tri-band.
There used to be a guy in San Jose that built really nice aluminum J-Poles for 2 meter, 220, and 70cm. He sold them at the Foothill College radio flea market many years ago. I had a few of them and they were good antennas. Solid aluminum elements, well made.

Of course that was a long time ago. The radio flea market was bounced around to NASA and then De Anza. I haven't been in 2 or 3 years. Not sure if the guy is still around or not.
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Old 05-26-2017, 2:31 PM
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Originally Posted by MaximusTheGreat View Post
They must be smoking crack! $125 for a small 5 beamer, yeahhhhh I'll pass. I'll stick with my effective Jpole.
If money is an issue, you can build your own small beam out of a tape measure! Just check for plans online.
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Old 05-26-2017, 3:39 PM
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If money is an issue, you can build your own small beam out of a tape measure! Just check for plans online.
What are your thoughts on a regular beam vs a log periodic antenna?
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Old 05-26-2017, 10:43 PM
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Quote:
Originally Posted by MaximusTheGreat View Post
I can vouch for the Ed Fong dual band antennas. The best part of it all is that it's shipped in a small sandwich bag. All you need to do is buy the recommended PVC pipe grade (in the instructions) at Lowe's or Home Depot for a few bucks. Slide it in and it's done.
Given the choice of an Ed Fong DBJ1 vs one of the ~ 6' verticals from Comet/Diamond/Jetstream which would be better? I'm looking at getting a Jetstream JTB3 which is only $18 more than Ed's antenna.
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Old 05-27-2017, 5:35 AM
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J-pole antennas are an end-fed half-wave antenna. Their gain is about the same as a dipole.

If you are referring to the Diamond X50 or Comet GP-3, they are decent amateur radio antennas. Don't be wowed by the gain numbers, though. The Comet and Diamond antennas typically use dBi even though they often don't clearly state that. To convert from dBi to dBd, subtract 2.1. For example, Comet says the GP-3 has 4.5 dBi of gain on 2m. That's 2.4 dBd.

dBi is gain relative to a theoretical isotropic radidator (a single point that radiates equally well in all directions). dBd is gain relative to a half-wave dipole.

I would avoid the Jetstream antenna as it's a Chinese knock-off of a Diamond/Comet antenna. Inexpensive, but I question the build quality and long-term reliability. That said, the Achilles heel of most fiberglass radome vertical antennas is the joint between the radome and the base. If the antenna flexes in the wind, that joint will weaken, loose its seal, and allow water to enter the base of the antenna resulting in poor SWR and corrosion.
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Old 05-27-2017, 5:59 AM
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A log periodic is designed to be wide band, forsaking gain. A beam for 2 mtrs is extremely easy to build...plans a plenty on the www!
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Old 05-27-2017, 8:45 AM
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Quote:
Originally Posted by W9BU View Post
If you are referring to the Diamond X50 or Comet GP-3, they are decent amateur radio antennas. Don't be wowed by the gain numbers, though. The Comet and Diamond antennas typically use dBi even though they often don't clearly state that. To convert from dBi to dBd, subtract 2.1. For example, Comet says the GP-3 has 4.5 dBi of gain on 2m. That's 2.4 dBd.
Thanks much! Converting the gain to dBd, the X50 and GP-3 is about the same as a dipole. Maybe I should just build a 2M vertical dipole first and keep my $$ in my pocket.

Last edited by W9BU; 05-27-2017 at 5:22 PM.. Reason: fixed quoting
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Old 05-27-2017, 9:24 AM
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A J pole is easier to build, and conceal. Twin lead is still easy to find, and plans for J poles and Slim Jims is all over the internet
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Old 05-27-2017, 1:11 PM
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Originally Posted by AI6VX View Post
Thanks much! Converting the gain to dBd, the X50 and GP-3 is about the same as a dipole. Maybe I should just build a 2M vertical dipole first and keep my $$ in my pocket.
Just build a simple 2 meter ground plane! I once made one out of coat hangers and an old SO-239 connector! It cost me nothing and it took only about 15 minutes to build, and the performance was similar to a jPole!
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Old 05-27-2017, 5:25 PM
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A j-pole is easy to build, but they are 3/4 of a wavelength long, so you have to deal with the height. If you build one out of twin-lead or ladder line, as if often suggested, you have to support it somehow. Alternatively, there are lots of plans on the web for building one out of copper plumbing pipe and those work fairly well. One thing to keep in mind about j-poles...they lower section where the two elements are parallel to each other is a transformer. That transformer can be disturbed by nearby metal.

A ground plane is only a little more than a 1/4 wavelength long. You can build one using an SO-239 chassis mount connector and some welding rod.
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Old 05-29-2017, 2:57 PM
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Quote:
Originally Posted by AI6VX View Post
I thought Ed's antennas were also known as a Slim Jim ?
No... Slim-Jim antennas are offered by N9TAX
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Old 05-29-2017, 8:15 PM
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BUILD A GROUND PLANE ANTENNA FOR 2 METERS AND MORE - SIMPLE AND EASY!
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Old 06-01-2017, 12:36 AM
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Quote:
Originally Posted by W9BU View Post
A ground plane is only a little more than a 1/4 wavelength long. You can build one using an SO-239 chassis mount connector and some welding rod.
Thanks to both. Just received my TM-281A yesterday - no antenna for it yet so I'm going to give one of these DIY 1/4 wavelength ground plane antennas a try.

Question for you guys - is the bandwidth wide enough to have good SWR (< 1.5) over the whole ham 2M band?
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Old 06-01-2017, 9:45 AM
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For most 1/4 wave antennas the SWR is good over the whole 2M band. Use good coax and don't use more than you need. Get the antenna up as high as feasible. Don't forget to weatherproof. Watch the RF exposer limits and remember PEP is 4 times average.

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