G5RV Jr. (Half Size) Ham Radio Antenna

Picture of 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.
y 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.
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Step 1: The components of the antenna

Picture of 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.

kb3zhx1 year ago
Thanks Bryan,

I cut the full size G5RV to match your dimensions listed here.. and Wow! It fits nicely as a flat-top dipole in my yard (hanging up about 30 ft high - attached on one end to a tree and the other to the house.) I have to do some fine tuning, but it works wonderfully on all bands with a tuner - except for 10 meters where it is perfectly resonant in the cw portion of the band. Worked qrp to Argentina and Chile during a 10m band opening!

Q: What is the exact length of your 450 ohm ladder line? Mine ended up being 16' 8" Maybe a fine tuning of this length would help it to resonate better on more bands??

Since the wire size of this MFJ-built antenna is kind of over-kill for back-packing, I'll definitely be making a lighter version of this for field use.. Keep up the good work!

73 Brian KB3ZHX
kb3zhx1 year ago
Thanks for the great info... I bought a G5RV (full size) antenna from HRO recently for temporary field operations. Now that I haven't used it in such a long time in the field, I want to cut it down to a G5RV Jr. so I can fit it on my property for a permanent install.

Anyone try this before? Seems the dimensions here will work and I'll just be cutting all wires approximately in half to convert the full size G5RV to the Junior model since it is fed with the same 450 ohm ladder line.
kc8hps (author)  kb3zhx1 year ago
Hi Brian, Bryan here kc8hps,

Thanks for the comment. Yes I think the half size is easier to transport. I could have used a narrower gauge of wire but sticking with the phosphor bronze It was the only size I had in the old wire bin :)
I tend to recycle/re-purpose things as much as possible.

I think in your case where you have the 817 for your mobile (read your qrz page) I would make a half size version you could put in a ziploc back and take with you on a day long hiking trip?
73's k8chps Bryan
FN641 year ago
Great "ible".. Would like to see more "ham shack knowledge" on here..
I have used acid core many times on antennas.. what you need to keep it away from are circuit boards, components, chips etc. I've never seen a problem on dipoles, j-poles or the quarter waves made on an SO-239.

My current 80M dipole is made from galv. 12.5 gauge electric fence wire.
It's balun fed & kinda in an inverted vee config... I say kinda because the apex is off the feed point by 6-8 feet.. apex runs thru a chunk of PVC pipe lashed to a tree. The tree can sway and the PVC allows the wire to slide at will. 3 years & holding strong..

kc8hps (author)  FN641 year ago
As I have time I plan to develop a collection of Ham antenna ibles.
I try to take pictures of every step so that I can put the ible together as I am able.

As you were saying about trees swaying. YES it is good to have flexibility, One of the hardest places to do that with HF is when you are mobile. If you have any brain stirs on that one please post something.

I will be posting a version of an HF counter poise coil that I have made for mobile use. (still untested) If it tunes well I will put it up here.

For those who read this, I am also a bit of a prepper/survivalist in a communications and energy sense.
I have been putting together something I am calling my "RF BOX" it contains all manner of useful things. portable wire antenna's, both HF and VHF/UHF etc.

I may do an ible on this item as well. 73 Bryan kc8hps
RangerJ1 year ago
Glad to see a Ham Radio Instructable. It seems like a natural combination.
Johenix1 year ago
Yes they still do make acid core and acid flux. I used it a few years ago when I replaced my own water heater.
You can use it (and probably should use it) when you make a "COPPER CACTUS" J-pole for 6 meters or above. KC0KBG

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