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Author Topic: Antenna Construction Question  (Read 301 times)
KI4HHE
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Posts: 9




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« on: November 28, 2004, 03:26:17 PM »

In another thread, someone suggested that the following antenna might help out with my HT.  I anticipate putting it my attic:

http://www.hamuniverse.com/2metergp.html

Here's my question, what technique is used to connect the vertical copper wire to the coax?

Russ
KI4HHE
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AE6RV
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Posts: 146




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« Reply #1 on: November 28, 2004, 03:40:13 PM »

Russ,

Look at the picture again.  Everything hangs off of the SO-239 connector.  You solder the vertical element directly to the center connector, and you connect the radials to the holes in the four corners of the connector.  The coax is just screwed into the bottom, just like the picture shows, using a PL-259 plug.
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K0BG
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« Reply #2 on: November 28, 2004, 03:40:16 PM »

Solder!

Actually, there are a bunch of ways you could make a 1/4 wave groundplane antenna. However, when you use an external antenna with a hand held, you're going to get mixed results. The reason (as has been published here about 100 times) is the HT is designed to work with a rubber duckie. Adding a lot of gain (or removing the losses the duckie has) will add greatly to the intermod and other problems. The best solution is to use a good mobile rig replete with power supply and a decent antenna.

Alan, KØBG
www.k0bg.com
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W7DJM
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« Reply #3 on: November 28, 2004, 05:05:38 PM »

Yes, and a caveat.  When I got started, just about all SO-239's and PL-259's were silver plated brass.

That means that you could solder to them, if you know how.

Nowadays, many less expensive and Radio Shack connectors are made of material of which I have not idea.  You cannot solder to whatever they are plated with, and sometimes you have difficulty soldering to whatever is UNDER the plating.

Worse yet, some of the flanges on the SO-239's I've seen are made of some cast pot metal or other, and you CANNOT solder to that junk.

Moral?  IF you DO have trouble soldering the ground radials on there, bend a loop in the end of the radial(s) and fasten with small screws.

You SHOULD be able to solder the center, but if you're using something like a coat hanger for the whip, scrape the end bare carefully, use a large iron, and some good flux.
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K1CJS
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« Reply #4 on: November 28, 2004, 05:57:29 PM »

"Worse yet, some of the flanges on the SO-239's I've seen are made of some cast pot metal or other, and you CANNOT solder to that junk."

I beg to differ, but if you know how to do it, it is possible to solder to just about any metal.  It does require special solder, a tight mechanical connection, the right soldering tools and also patience and practice, but it is possible.

On the other hand, it should be said that you should get high quality parts if you want your projects to work properly and last a long time, but too many people want to just get the parts the cheapest, fastest way.  In the long run, it costs more, much more then if the job was done properly in the first place.
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W7DJM
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« Reply #5 on: November 28, 2004, 08:06:12 PM »

Let's try and keep this in context, here, alright?   You can solder, braze, weld some pretty exotic metals, but 99.9999999% of the average ham/homeowner doesn't have the correct equipment.  I sure as heck don't have a TIG, for example.

Most novice hams are not going to have the skill or materials to solder these junk connectors, or they wouldn't be asking.

Off subject, however, for those who would like to build their own whips out of junker stainless whips, Harris welding products sells a little kit called "stay-Brite" that makes THAT pretty easy.
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N6AJR
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« Reply #6 on: November 29, 2004, 02:42:35 PM »

solder the center and use nuts and bolts to loops in the end of the radials mesure from the 45 bend to the end for you 19 1/2 inches you can also pop rivit the radials.. it ain't rocket scince..
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KI4HHE
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Posts: 9




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« Reply #7 on: November 29, 2004, 06:47:45 PM »

Not only am I new to ham, but I have never soldered anything.  Isn't it necessary to mechanically connect center to the SO-239 before soldering?  How do I do this?  Can I/Do I twist the center and the SO-239 together before to "mechanically" connect before soldering?  Thanks.
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KT8K
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Posts: 1490




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« Reply #8 on: November 30, 2004, 08:06:59 AM »

The SO-239 has a hollow pin (solder cup) for the center conductor which is deep enough to hold a piece of wire upright if it will fit.  Slide the wire down into the hollow pin and you can easily solder it in place.

Make sure the wire is fairly clean, with any paint or other coating removed.  Put some resin-core solder on the soldering iron tip and touch the tip to the wire to transfer heat.  Then touch the solder to the wire where it enters the hollow center pin until it melts and flows into the gap between the two.  When it has flowed in nicely remove the solder and the heat and let it cool.  A good solder joint is shiny and mechanically stable, i.e. it will not break loose if you twist, bend, or pull on the wire (but wait to try any of this until the joint is cool enough to touch, to make sure it is a good joint).  You can solder a stiff wire into each of the four mounting holes on the SO-239 with a similar technique.  All the wires should measure a quarter wave on the frequency of interest, or around 19.25 inches on 2 meters.
You will have an amazingly effective antenna, and you made it yourself!  Good reception & 73 de kt8k - Tim
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KI4HHE
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Posts: 9




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« Reply #9 on: November 30, 2004, 09:10:52 PM »

Thanks, Tim.  I that was what I was looking for.

Russ
KI4HHE
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