By rbodell in CircuitsElectronics
This is a simple base station CB antenna You can make in 30 minutes out of a bit of PVC pipe and fittings, some wire and a SO239 coax connector and a piece of coax to connect it to your radio. You should have a 1.5 SWR on this. You should be able to build this for about 10 to 15 dollars.
Step 1: Materials
Materials
MATERIALS
2 PCS 8'6" 12 or 14 gauge electrical wire
10' 3/4 Schedule 40 PVC pipe
3/4 inch PVC pipe cap
SO239 coax connector (see picture)
4 - screws or bolts to fit the SO239
I solder on eye electrical connector to fit screws on SO239 and wire
20' section of 1.5 inch Schedule 40 PVC pipe.
1 - 1 1/2" PVC "T"
1 - 1 1/2" PVC cap
1 - 1 1/2" x 3/4 PVC reducer
TOOLS
PVC cement
saw
drill
screwdriver
pliers
Soldering gun and electrical (NO acid) solder
electrical tape
sealant
Step 2: Assembly
Assembly
1- Strip back 1/8 inch insulation on wire and solder to center of SO239. Make sure solder joint is shiny. If it is dull, reheat it till thoroughly melted.
2- Solder electrical connector to end of second wire.
3- Drill hole in Cap to mount SO239 flush. Then drill mount holes for mounting screws.
Cut off 1 1/2 to 2 inches off the end of the 1 1/2 inch PVC pip[e and glue into base of T to mount cap (as shown in picture). Do not glue cap yet. Drill small hole in under side of the T for wire (see red wire in picture)
Glue in 1 1/2 x 3/4 reducer on top of the T
4- Insert wire that is soldered to SO239 into hole in cap then mount SO239 to cap with screws and a little sealant. Put eye of other wire under one of the screws. Tighten and put a little sealant over screw with wire under it.
5- insert wire under screw into hole on bottom of T (see red wire in picture) and out the bottom of the T
6- Insert wire soldered to SO239 in T and out the to 3/4 inch hole in top and glue cap to T.
7- drill hole in 3/4 pipe cap for wire.
8- cut a piece of 3/4 PVC about 8 feet so the wire will go through it, out the cap and have enough to tie a knot about 2 inches from the end. Glue it together.
9- run the remaining wire down the log PVC pipe and glue T to the pipe.
10- Attach lead in cable to SO239 and tape to protect from weather. Also tape to outside of antenna pole to keep it from whipping around in the wind.
11- Glue T to 20 foot section of 1 1/2 inch pipe.
Step 3: Set SWR
My radio has an swr meter on it, if yours doesn't you will have to borrow or buy one.
Your antenna should be away from metal objects.
If you want a taller mast use a metal pole or use guy wires.
The SWR should be ok with this if your solder joints are good.
Read your directions for checking the swr. Some meters you have to zero. mine is automatic when it is in the swr mode on the radio. I just have to key the mike to see the swr.
Check your SWR on channel 1 and 40. It should be around 1.5 across the band. If it is over three, you need to adjust the length a little bit at a time. If it is higher on 40 you need to shorten the tip about a quarter to half inch at a time. If it is high on 1 you need to solder a little on the end to make it longer. I have made about 20 of these and I haven't had to add anything to it. Most of the time I don't have to do anything to it.
Step 4: NOTES
NOTES
You can improve the range by making 4 horizontal reflectors 8'6" long below the T connected to the screw of the SO239, but this supposed to be simple and easy version. That gets more complicated.
If there isn't any skip, I can usually talk about 10 to 20 miles easily.
If you have a lot of trees around you, they can cut down on your distance too. You can put your antenna in the top of a tree to get height but make sure it is above the leaves.
It is a good idea to put a lightning arrestor in your coax someplace between the radio and the antenna. Also ground the chassis of the radio. It will also help you get out a little better. I have logged 16 different countries including australia on homemade ground planes, not because the antennas were some great invention or secret, it was because I had a very good ground. You can have a thousand dollar antenna 500 feet in the air but if you have a bad ground, you won't talk across town. I used to take my motorcycle with a 102 inch whip down near the salt water and throw a ground wire in the salt water and talk 40 miles down the coast from my motorcycle. Granted there were no trees but motorcycles have almost zero ground so they do good to talk a couple of miles at best. If you are around Bradenton Florida, go down on channel 2 and ask around for somebody who remembers Machismo. They will tell you I did that all the time just south of Tarpon Springs to Anna maria island. I also talked regularly from just north of Key West to Bradenton. over 100 miles because I had a copper ground plate under the boat in the salt water
FOR BEST RESULTS, MAKE SURE YOUR RADIO IS GROUNDED PROPERLY. IT WILL IMPROVE THE RANGE.
OK that is it, quit reading and get to work.
Later
Machismo.
