QTH.COM Swap Chat

just bought a dual band j-pole from alanmarcum.com(designed by wt9h)and cant get swr below a 3.0. The snap tee stand off is 10 inches above the base of the antenna as instructed and am using brand new lmr400 cable. The antenna is not near any metal and is mounted on a 5 foot mast about 30 feet up on a pvc pole.any one have any ideas why swr is so bad? How about how do I correct it? using on 2 meters with a Icom IC-V8000 . p.s. does this type of antenna need to be grounded if so how?

Hello Rory,

My first question is, "What Manufactures Model Number is your Wattmeter?"

Is your Wattmeter designed and qualified for measurements on 2 meters (144MHz ~ 148MHz) & 70 cm (420MHz ~ 450MHz)?

Have you put a known good 50-Ohm Resistive Dummy Load attached to your Wattmeter Output and then on the LMR-400 Cable connector that attachs to the J-Pole antenna Input connector?

And "What type of Coaxial Cable are you using between the transceiver Output and the Wattmeter Input and Lenght?"

Dan
WA9WVX

Hello Rory,

I kept thinking about your High VSWR 3:1 problem last night, in fact it kept me awake all night. I pulled out my ARRL reference books and read about the J-Pole design but when I fired up the computer and searched the Internet about constructing these antennas I started question whether your antenna may have been built wrong as far as the RF connector termination. Whoever was building the antenna could have been easily distracted by answering some questions or having to stop to take care of another priority. When the individual proceeded on the J-Pole antenna inadverrtantly switched the center conductor and shield wires which would cause major VSWR problems.

I'm including a DXZONE / ARRL web page link discussing a VHF / UHF J-Pole design:

http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=9295

Click on the A J-Pole for 2-meters and 70-cm which will automatically redirect you to the correct webpage. This may help you understand the antenna design.

73,

Dan
WA9WVX

swr meter is a mfj vhf model 812b. also checked it out on a antenna analyzer and got similar results. also found impedance went to almost 70 ohms over the 2 meter spectrum. I have included a link so everyone can see this antenna because it is not your every day j-pole http://www.alanmarcum.com/jpoles/jpole.html

Hello Rory,

I went out to look at the Dual Band PVC J-Pole Antenna long before I wrote my first reply to you. All that I see is a PVC Pipe & Connectors and this doesn't provide how the electro-mechanical components are constructed within the PVC Pipe. This is why I provided a web link so you could disassemble your antenna and compare how it was built.

Furthermore "if" you haven't contacted the person selling these antennas, I will suggest to contact them and describe your problem. How would you expect any of the Hams that frequent this website to make a good judgement on that product without having one in their possession? You could have received a Defective Product and not have any idea that this could have happened!

Ninety percent of amateur radio operators always have a natural curiousity how their radios, accessories and antennas are made. I have a feeling you're a Plug and Chug Operator and don't have a clue about how things work. You may want to purchase a copy of the ARRL Handbook & Antenna Handbook to read and better understand the equipment your trying to use and operate.

Good Luck,

Dan
WA9WVX

Hello Rory,

I'm providing several Amateur Radio & Commercial LMR Antenna web sites for you to review Dual & Single Band Antennas specifications. You will need Adobe Reader or FoxIt to view the following pages for Base Station Vertical Antennas for FM transmit and receive operation.

Hustler (Amateur Products)

http://www.new-tronics.com/main/html/ba ... -270r.html

http://www.new-tronics.com/main/html/ba ... 7-144.html

http://www.new-tronics.com/main/html/ba ... -144b.html

This Hustler antenna listed below has the closest specifications to a Commercial Product.

http://www.new-tronics.com/main/html/ba ... meter.html

Cushcraft AR-270B (Amateur Products)

http://www.cushcraft.com/comm/support/pdf/AR270.pdf

Hy-Gain V-42R (Amateur Products)

http://www.hy-gain.com/Product.php?productid=V-42R

Click on the words: Download Manual to get an idea what this antenna looks like and the construction.

Phelps-Dodge became Celwave and now is RFS (Commercial Products)

http://www.rfsworld.com/index.php?p=354&l=1

Scroll down & Click on:

Browse the Omnidirectional Antenna section of our print catalog

Scroll down the page to the Stationmaster Model # 220-2N and read the Commercial Specifications on this antenna. Frequency Range: 142 MHz ~ 150 MHz (most likely tuned at 146 MHz)

TX RX Systems Inc (Commercial Products)

http://www.txrx.com/product/product_vie ... 4DED449D10

Scroll down to the Datasheet and Click On this field.

After you have reviewed all of the Amateur Radio & Commercial LMR antenna web sites, go back to the supplier you chose to purchase his Amateur Radio Product and think about what he has supplied to the consumers. And consider Alan Marcum’s personal statement: “Although no one ever has, if you are not satisfied with the antenna please let us know and we will make it right.”

http://www.alanmarcum.com/jpoles/jpole.html

I think you need a local (experienced) Amateur Radio Operator to be an "Elmer" and help guide you through Troubleshooting any problems that you're experiencing with Ham radio equipment, accessories and/or antennas. You're not the first person that needs advice or help setting up a Ham Radio Station nor the last.

One last thing I've done is to look up Hams that possess at least a General or an Extra Class License living in Palmer, MA. Perhaps to assist you as an "Elmer". Here are the Call Signs, Names and you will be required to contact the individuals for the necessary help.

WB1FKT DOUG AUVINE 35 ST JOHN ST PALMER MA 01069
WT1W ED LIBERA JR 1586 WARE RD PALMER MA 01069
KB1EEJ Jared Greenberg 58 Mt Dumplin Rd Palmer MA 01069
KA1TFU ED MIDURA 528 OLD WARREN RD PALMER MA 01069
N1WCW DENNIS MALLETTE 69 QUABOAG VALLEY PARK PALMER MA 01069


Good Luck,

Dan
WA9WVX