Homemade Dipole, High SWR?

[office888]

Decided to try to make my own 11m dipole.

Used an SO239 "Tee", and 2 x 239 fittings. I split 16ga lamp wire down the middle. Each leg is 103.25". I soldered one side to the center signal fitting, and the other to the outer ground fitting.

So then I went to check the SWR before I hung it up. I laid it out, and checked it with TWO different meters. SWR overall is high, almost 10:1.

Any ideas? Do I need a Balun?

-Richard-

 

[Marconi]

check for a short

 

[Jay in the Mojave]

Hello Office 888:

You first sentance is hard to follow. What are 2 x 239 fittings???

The SWR will be high just laying on the ground. This is not a good SWR test.

Its a know fact that dipole antennas as most all antennas will change SWR when the heigth is changed.

The SWR will change with heigth, but if your not using a Balun the SWR can get crazy and not work to well. Some dipole antennas without a Blaun will seem to work, but all my experiences show the use of Current Balun is a good call.

The ARRL Antenna Book and Radio Handbook show how 1 to 1 Current Baluns are used and made.

Best 1:1 Balun 1.5 - 54MHz Dipoles & Yagis 5kw - #1115
Transmitting Baluns
BALUN UNUN

The higher the dipole antenna the better.

Good Luck

Jay in the Mojave

Upate: Here is a great paper on the Balun, and its uses.

http://w2du.com/r2ch21.pdf

The Book Reflections II is well worth the Doe Ray Me.

Jay in the Mojave

Decided to try to make my own 11m dipole.

Used an SO239 "Tee", and 2 x 239 fittings. I split 16ga lamp wire down the middle. Each leg is 103.25". I soldered one side to the center signal fitting, and the other to the outer ground fitting.

So then I went to check the SWR before I hung it up. I laid it out, and checked it with TWO different meters. SWR overall is high, almost 10:1.

Any ideas? Do I need a Balun?

-Richard-

 

[HiDef]

The antenna needs to be checked in it's operating position or the test isn't valid. Drooping the ends into an inverted V might be necessary for a 1:1 match.

Plan to put it up and take it back down a few times. This is the price we pay for the simplicity of a coax fed resonant sky hook.

Make a coax coil BalUn from the existing feedline. No need to buy anything. All you need are a few turns at this freq. Plenty of info on the web about that.

 

[Beetle]

check for a short

What Marconi said. Use a multimeter and check at the radio end of the coax. You should see infinite resistance between the center and shield. If you see any measurable resistance, you have a problem either with the connections you made, or with the coax itself.

Get some regular wire antenna insulators. UHF connectors aren't designed to be insulators by themselves, and they're expensive. Insulators are cheap.

 

[Quiksilver]

Do you have pics of your connections? Sounds like a short as previously mentioned. Should look similar to these:

Or if you used the SO-239 tee, it should look like this.

 

[freecell]

the radiation resistance required for a reasonable match is non-existent as long as it's laying on the ground.
Dipoles, Radiation Resistance

 

[mackmobile43]

http://www.hamuniverse.com/easydipole.html

 

[Beetle]

Do you have pics of your connections? Sounds like a short as previously mentioned. Should look similar to these:

Or if you used the SO-239 tee, it should look like this.

Quiksilver - I would DEFINITELY put some insulating sleeving or at least some tape on the lead going to the center of the SO-239. Hanging that up as it is is an open invitation to the wind gods to blow the whole thing around until you have a complete short at the feed point.

Also, if you're happy with the performance of the antenna, I'd suggest you solder the places where the wire is wrapped around itself. It has a tendency to stretch a bit anyway, and soldering things will keep the resonant frequency from getting significantly lower than it is, at least for a while. Just enough soldering to keep things from pulling apart.

 

[Quiksilver]

Yeah,
That was just a temp setup that's long since taken down. Definitely would have done what you suggested if it was up longer.
Thanks!

 

[packrat]

I never bother using an so-239, or any connectors at the antenna, I just wrap the coax on the center insulator and solder the legs to the elements where they are connected to the insulator. Strong, Cheap, Easy and lots less to go wrong!!!

FWIW


PR

 

[W5LZ]

Just out of curiosity, what problems have you had with SO-239 or PL-259 connectors?
- 'Doc

 

[packrat]

OH, lets see... connectors that come loose in the wind, water intrusion since they are not weather proof, corrosion from exposure...

PR

 

[Jay in the Mojave]

Upate: Here is a great paper on the Balun, and its uses.

http://w2du.com/r2ch21.pdf

The Book Reflections II is well worth the Doe Ray Me.

Jay in the Mojave