O.K. I took a Junction box or some kinda electrical box that you can remove the caps by bending it to break. Anyways, I mounted on a Gumball mount into one of the holes, used the wire clamp and inserted one of the groundplane rods from my Starduster and clamped it into the junction box, then screwed on my homemade fightingsticks from my starduster groundplane rods. It is in a "L" like configuration. I was wondering if this will make it directional or omni????
Both elements are the same lenghts. I used my SWR meter and it read 1.5:1 SWR.
All I wanted to know if it will be directional if I have only one element on one side of the antenna?
Most of the interference/RF interference with this setup have disappeared as when I had the partial stardust up. But, just waiting for some condition to test it out if it really works well.
Thanx, James. Ill try to get some pix by tomorrow.
Hey
15minigrass, Nice job of home-brewing an antenna! Feels
FANTASTIC to talk on your own creation, doesn't it!?!
OK, I'll try to shed a tiny sparkle of info that I know 'bout dat 'ting.
You should maybe bend your radial down 30* more. - Why?
OK, two 1/4waves at 90*(degrees) like you have it, makes it about a 37ohm impedance antenna, not 50 ohms like your radio wants for a 1:1 swr, that's why you have 1.5:1.
Since 25 goes into 50 twice, if it was a 25ohm impedance you would have a 2:1 swr, and since 37ohms is ~1/2 way from 25ohms to 50ohms you are half way to 2:1 swr.
At 180* (one straight up & one straight down) you would have about 75 ohms which is also 1.5:1 because it's 1/2 way to 100ohms from 50ohms. 100 ohms would be a 2:1 since 50ohms is 1/2 of 100ohms and 50 goes into 100 twice.
BUT - at 120* it should be right about 50ohms where you would get that beloved 1:1 swr!
- So, you can bend down the radial on the side to about a 30* down angle and watch the swr fall close to 1:1!
...or you can try a shunt to ground.
To build a shunt just take two 9" pieces of copper or brass welding rod and connect one to the top 1/4 wave and the other to the radial or ground on the box near the top 1/4wave element.
- Try to keep the two rods parallel to each other and about 1.5" apart.
You might find it needs to be more like 1" or maybe even 2" apart, but it should end up around 7"-8" long and ~1.5" apart.
Then:
Cut a little piece of copper wire about 2.5" long and bend around about 1/2" on each end so it becomes 1.5" long with a little loop on each end, to connect over each of the rods making a long U-turn.
It's a shorting bar - to short the rods together in such a way that you can slide it from the outer ends of the two rods closer and closer to the 1/4 wave element & ground until your swr goes flat.
You should be able to cut off the overlapping ends once you find the 1:1 tuning point and solder it there.
Your basically tuning out the reactance by making a little 5" to 9" U-turn out of the two rods and the copper slider, which basically shorts the top radiator to ground.
It looks like it would be a dead short to your wattage but it isn't, because RF isn't going to act like DC.
Your wattage will prefer the 50ohm antenna to the weird impedance U-turn to ground so your wattage will get radiated but your antenna reactance will flatten out - which is a good thing.
Plus, you should find this sends more of the static to ground instead of down the coax to your radio!
+++++++++++++++++
Another observation, in the direction the radial points you should get a lower take-off angle for your signal and that would help you to talk longer distances locally.
In the other directions you should have a higher angle which might help you to DX if the DX is closer than further, like maybe Calif or other even closer DX contacts.
High angle is good for 'Sporadic E' like maybe 500-1000 miles, where low angle will get you longer DX like into the East Coast of the USA, or Europe.
Personally, I'd prefer a bent down radial (to about 120* down from the top element) for what is a little more gain than the 90* 1/4 wave ground plane you've got there, and an overall lower take-off radiation angle.
- At 120* it becomes a 'Center-fed 1/2 wave Dipole'.
And you can still experiment with a ground shunt if you want to try to make a quieter 120* DIPOLE antenna.
I hope you're now
less confused after you read this than I am after writing it...
73!
