Intro: G5RV Jr. (Half Size) Ham Radio Antenna
This project gives instruction on how to build my version of the G5RV wire antenna that is used on the 10-40 Meter Ham Radio bands (28MHZ to 7MHZ).
The history and basic theory of this antenna dates back to 1946. It was invented by Louis Varney. More technical information can be found at the following link . I WOULD STRONGLY ENCOURAGE YOU TO READ THIS LINK and vew it's contents including the diagram so that you have a mental image of where we are headed.
By Googling G5RV will also give you information and other ways to make and use this antenna.
Let me clarify that I DID NOT INVENT this antenna, I just built my own version of the original.
I have not posted yet a picture of the antenna in it's final hanging location as this is going to be a portable antenna that will be put up and taken down likely in the same day.
Step 1: The Components of the Antenna
The wire used for this project Is green UV resistant vinyl coated, phosphor bronze stranded wire.
You could use any copper wire but note that pure copper wire will stretch over time more that what I am using. When wire antenna's stretch that also de-tune downward in frequency as they become longer.
The bronze wire is extremely strong and will last a life time, I'm sure it's weight rating is way over 1000 lbs.
For this antenna you will need two pieces of wire 26Ft long. 25.5 is the finished length aprox. I have extra to get around the insulators and to wrap and solder.
I chose to use ceramic egg style insulators for several reasons. Most of you would look at these and say WOW that is overkill! First off I chose them because they were all I had in the junk box and I didn't want to invest more money at the time.
I also wanted to have insulators that had weight to them so I could put one end of the antenna elements over a tree limb if there was an emergency or I was in a hurry if needed. This way if it was bad weather I could let it hang and not need to tie it off as I normally would do.
Since the insulator electrically separates the RF energy on the antenna element/wire from the non conductive support it needs to keep the two from touching. Often when transmitting on certain frequencies there will be a very high voltage at the outer ends of the antenna. This voltage can start a fire or melt a plastic insulator if not installed correctly or the wrong insulator is chosen for the job.
It is not impossible to have several thousand volts at the end of an antenna. NEVER touch an antenna while it is in use unless you know what you are doing!!!
I chose a 4way 1/2" pvc junction as my center insulator. I did this mainly to facilitate supporting or hanging the antenna from the middle (which should always be higher than the ends.)
With this insulator I am able to insert 1/2 pvc pipe to support from under or over the antenna to hang from, how ever I choose. Use your imagination on this and you can dream up a number of ways to support this antenna.
I will use a piece of 550 Para cord run through the open ends to hand the insulator allowing the Ladder line to drape downward to the ground. It is advisable to hang this antenna as high up as possible. Getting its at least 20 feet up on a tree branch or some other non conductive support would be suitable.
The Ladder/Window line is aprox 450 Ohm impedance. You will be using 16.5 ft of this line. I suggest cutting it 6-8 inches longer so that you have room to make attachments with solder at both ends. With the use of an HF tuner between the transmitter and the antenna any finished length between 15.3 and 16 Ft should give you a good SWR match on all bands.
Lastly (NOT SHOWN) you will need a piece of 50 Ohm Coaxial line. RG-8, RG-8x, RG-58U will all work depending on the wattage you plan to run with and the length of the cable, and loss you want to incur. An RF fitting to match the antenna output of your tuner will be needed these are usually PL259 , N type, or BNC connectors.
Some articles about the G5RV say you can use any length of coax you choose. This is a disputed fact so you may have to play with the length to get a good match.
Step 2: The Tools I Used
As you saw in prior pictures I used a small butane pen touch to solder with. You could use a 100watt iron but this pen torch was easier. Honestly the soldering iron will need a lot of time to heat up this amount of metal and get a good joint. You can purchase the torch for a few bucks at Harbor Freight you will also need a can of butane that you refill lighters with. also a couple bucks at places like walgreens, wal*mart and the like.
Since I have a back ground in metal work, soldering etc I chose the torch. JUST BE CAREFUL the torch is much hotter and will melt things you dont want melted. NEVER leave your lighter or butane bottle near your soldering site where the torch could graze them and make them explode!!! SAFETY FIRST !!!!!!!
I am using the thin 60/40 solder from RadioShack. This solder you can feed to the joint fast and have better control. With all solder connections FLUX is the key. You want to keep the copper from oxidizing before the solder flows. If the copper is dirty/oxidized the molecular bond will not solidify and you will have a "COLD JOINT". COLD JOINTS are a real headache in radio land.
Resistance, arching, lack of strength are all things you don't want on a fun outing or in emergency communications.
You may have noticed I am using electronic wire clippers. these are handy for trimming the ends of wire sticking out from solder joints. Cutting ladder line insulation out to allow passage over the 4 way PVC center piece.
I use an old style hand crank drill for all my holes. (drill not pictured)
The blue clamp in the picture did a nice job holding the ladder line to the table/soldering block so that the torch work was safer and easier.
****** I also keep a small wet sponge near by for cooling joints and in case something drips or spills.******
Step 3: Putting Things Together Pt 1
I think these three pictures speak louder than words.
You want to drill holes in each ends and both side of those ends that fit the gauge or wire you are using.
I as you can see trimmed extra insulation out of one window space in the ladder line. This allows the conductors to go over the center insulator like a pull over vest. This creates a nice support for the feed line and also takes stress off of the solder joints.
The zip ties do a nice job of keeping things in place without the use of glue, tape, or cement.
NOTE **** Since I am not permanently installing this antenna, I will not be taping or sealing joints at either end of the elements.**** <<< I want to see that the joints are in good shape when I take down and put up the antenna on each use.
As you can see from a close view you can see there will be several ways to hang this antenna from the middle.
Step 4: Putting Things Together Pt 2
Soldering the feed line ends to the dipole elements can be a chore if you are new at it.
As I said before clean well fluxed metal is what make the job easy and the end result strong.
For those of you new to soldering. MAKE SURE you purchase solder paste/flux separate from the flux that is in the middle of some solders. I happen to use Oatley's brand but any resin flux should do. DO NOT USE ACID CORE SOLDER WITH ELECTRONIC SOLDERING. To be honest I don't know if it is still made but if you have it don't use it for this type of project!!!
Fluxing the joints before heating will insure the metals to be soldered remain, or become clean.
a small soft water color paint brush, tooth pick or scrap of wire will work nicely to apply solder. don't be afraid of the flux, it's cheap and cleans off with warm soap and water after you get done. Make sure the area to be soldered is pretty well covered in a light amount of flux.
I have posted 2 images here of the joints. The first picture shows the wires wrapped around one another with the flux applied. In the second picture You will notice how the solder flowed and created rounded connections between the metal types. This is called capillary attraction. When you see this happen you know the solder and the joint was hot enough to make a good solid molecular bond. This will assure that maximum antenna voltage and current can pass through with out being hindered by resistance of some sort.
The idea of a good antenna is to get as much RF ( Radio Frequency) energy from the transmitter up the feed line, down the element and radiated into the air. The last thing we want is a road block or a lane closed :) I think you get the idea!
When you are done soldering use your clippers to trim the solder joints. Often there is a wire end or ends that need to be trimmed a bit. Doing this keeps you from getting a cut on your hand or finger. It is a nice bit of house keeping before you wash the joint with your wet sponge.
The sponge will take a lot of the flux residue off of the joint. If you want the joint real clean proceed to the sink with a drop or two of dish soap in your fingers and clean it that way, then rinse and dry.
Step 5: Putting Things Together Pt 3
You are almost finished!
You will need to solder your coax to the other end of the ladder line. The image on the link above shows the coax directly soldered to the ladder line. I chose to use a UHF SO239 connector out of the scrap box. You can also buy these from Radio Shack or on ebay at times.
If I had had the money and wanted to take the time I would have enclosed this connection in a plastic project box. (Again Radio Shack). It would have made it look nicer and been perhaps safer in the long run.
By using the SO 239 female I can use any coax PL 259 coax I choose. It can be short, long, low loss like RG 9913 or RG 58u mobile type coax which is quite lossy for long runs ,yet very flexible. ( Coax loss at HF frequencies is fairly low dB wise.) If I was doing this at VHF-UHF I would not even use the connectors because each has a loss component.
If I had a location other than my 3rd floor apartment I would permanently install this antenna. At that point if the feed line run was long I would likely use Low loss Hard Line to keep the loss to a minimum.
You now have a visual of how I did my version of the G5RV multi band dipole.
I would encourage you to dream a bit about which version , be it DOUBLE size for all 6 bands, FULL size for 5 bands, or Half Size "JR" for the 4 bands that you want or need to build.
Keep in mind this antenna can be built very light with smaller stranded wire or TV Twin Lead so it can be rolled up and put in a back pack for that hiking trip using a small CW transmitter for QRP << very low power.
I would enjoy hearing from you if you build or come up with other ideas for this antenna. Questions are also welcome along with comments.
As I use this antenna I will try to take some station picture so you can see it up and in action.
Thanks for reading this instructable!
kc8hps ***** More about me and my interests can be found at kc8hps.com