Delta Loop Antenna 10m-11m + Balun 4:1
As i really enjoy using the 10m band and sometimes the 11m band to talk with friends around Athens, it came as a must of constructing a new antenna. Also i wanted to do this because i have an Albrecht 5890EU ,which operates in these frequencies and i didn't have an extra antenna to operate it.
Due to the lack of space in my QTH(that is why i 'm using the long wire + UnUn antenna), i was trying to find a solution of a vertical polarization antenna ,with high efficiency and as small as possible.
|Albrecht 5890EU 10m Amateur Radio Band(30W FM-SSB)|
After some research i came across the Delta Loop antennas which are tested and working from many amateur radio operators around the globe.
So what do we need:
1) Electrical wire(coper)
2) a 4:1 balun
3) and some space!
W3GAS has a great calculator in his website so this is a good starting point.
Insert your desired frequency and the calculator will tell you the total length of the wire needed as well as the length of each side o the Delta.
This is actually the easy part because you just need to measure the wire needed and cut it. The "tricky" part is the construction of the 4:1 balun that will match the impedance of the delta loop to the 50Ω impedance of your transceiver. Well you can always go and buy one and spend 40-50 Euros, or you just can spend 30 minutes of your life and 12 Euros for the components to build it your self. I've chosen the second option...as always.
What will you need:
1) Copper wire
2) Toroid T200
3) A waterproof electrical box
4) Drilling tool and/or Dremel
5) Two contacts RED-BLACK
6) Two metal hinges
7) Soldering Iron+Solder
8) One female chassis PL connector
...and we are ready to go
First you have to start by winding the copper wire(in pair) around the toroid 18 times and making the connections as shown in the following schematic.
|How to wind the copper wire|
After you finish with this step you can test your balun by connecting a 300Ωhm carbon resistor and have 1:1(or close)SWR from 1.8 to 28 Mhz. You will need an antenna analyzer for this test. Following there are pictures of my construction to help you make yours.
The setup of the antenna is very bad but i do not have space. Never the less it works like a charm!!! With 1.0:1 to 1.3:1 SWR measurement from 27 - 28.5 Mhz.
|I've highlighted the wire|
Finally the finishing touch!
Remember ,in order to achieve vertical polarization you must place the Delta within the X-Y axis, and feed it from one of the bottom corners! If you want horizontal polarization place the Delta in the Z-X axis.
For any questions please contact me at firstname.lastname@example.org
PS: I will make a different post for the performance of the antenna with some videos and SWR , Impedance measurements with the antenna analyzer. Please give me some time! In general the antenna works as it should 15-20db up for the stations that transmit in vertical polarization plus it has less static noise than a standard dipole.
Attention!!! Due to the physics of Delta Loops do not touch the antenna while transmitting, the currents are many times stronger than those in a simple λ/2 dipole antenna.