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BSOSCBlog.com • View topic - 2 meter base station .. J pole antenna

2 meter base station .. J pole antenna

2 meter base station .. J pole antenna

Postby montanamac » Mon Feb 08, 2010 11:43 pm

For those of you who are new to the world of Ham radio and are in the process of setting up you first radio to use as a "base" station ... here are some answers to questions you might have.

Many of the BSOSC members were involved in the workshop activities where we built several "J pole" antennas. Some have already installed their new antennas and are on the air. Others are just getting ready to set up their station. The following are some comments that might answer some questions and help you get up and running.

As a general rule ... the higher the better for your J pole antenna ... within reason. The J pole is an omni directional antenna and needs to be mounted vertical with the "J" on top and the single copper pipe on the bottom. The bottom copper pipe needs to be connected to a support to hold it in the upright position. What can you use for a support ... steel or heavy wall PVC pipe, wood (something like a 2 x 2 or 2 x 4), and about anything else you can attach the antenna to that will hold it vertical and secure.

The closer you mount your antenna to your radio the less it will cost you for coax cable and the less line loss you will have. Measure how much coax you will need ... from the antenna to your station. (allow and extra few feet ... better to be 3 feet too long than 1 foot short)

One of the easiest methods I have found is to use a piece of pipe for the support and secure the bottom pipe of the J pole to the support pipe with a couple of hose clamps with the pipe laying on the ground or resting on a chair or something to make it more convenient than working on the ground.
After the J pole is secured to the pipe it is time to attach the coax to the antenna. After securing the PL-259 connector to the coax cable (don't forget to solder the center lead to the connector) insert the connector into the fitting on the J pole and tighten the threaded part of the fitting. The coax cable will be at a right angle to the antenna. Next, make a nice arc in the coax and attach it to the base of the J pole or the mounting pipe using black electrician tape or cable ties or something similar. The goal is to secure the coax so the wind does not move the cable back and forth and put undue strain on the connector that is soldered to the antenna. Now, secure the coax to the pipe in several places along the length of the pipe (every 3 feet should work).

You are now ready to stand the support pipe up. Make an indent in the dirt an inch or two deep to hold the bottom of the pipe from moving side ways. Have a pipe clamp or other method ready to secure the support pipe to the building. Stand the pipe up and secure the pipe to the building. Having a friend to give assistance will help a bunch if the support pipe is fairly long.

You are now ready to route the coax cable into the area where you intend to have your radio. If you will be drilling holes for the cable you might want to wait to install the other PL-259 connector til the cable is through the wall and near your radio (the cable is smaller than the connector so a smaller hole will be needed for just the cable). Install the PL-259 connector (don't forget to solder the center wire) and hook up to the back of your radio.

All of the J pole antennas we built have worked out well. However, it is always a good idea to make sure your antenna is well tuned before transmitting. Call Mac or someone who has an antenna analyzer to check your antenna and feed line to be on the safe side.

Just a comment on coax cable. There are all kinds of coax ranging from poor to good in quality. The better the coax, the better your new rig will work and work well for years. Jim is currently stocking a very good quality coax (LMR 400) at a super price. Sales info claims a 20 year lifetime.

Well, that should get you up and running. I will add some more as questions arise

Mac
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Re: 2 meter base station .. J pole antenna

Postby jpf1030 » Tue Feb 09, 2010 3:28 am

Thanks Mac for posting the helpful j-pole antenna info. We still have 9 of the j-pole antennas the BSOSC group built in the last antenna building class. These antennas have all been tested on Mac's antenna analyzer and are good to go. Everyone that has one of these homemade antennas has had great success with them. The remaining antennas will be available on a first come, first served basis. The materials cost for the antennas was $23. each. We will accept any donation amount over the cost of the materials. 100% of the donation will be turned over to the BSOSC group treasury for BSOSC projects...Jim
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