Here is a plan for homebrewing a 2 Meter Square Dipole plan. The advantage of this antenna is that it is unidirectional, and it takes less space than the regular 2 meter dipole. The calculation included on the diagram below is for building the antenna using copper tubing, you should use MMANA-GAL or other antenna simulation software to come up with new dimension for other materials (aluminium, wire, etc).
Click on the diagram to enlarge it. Hopefully this will help you in brewing new antennas! Original plan taken from KOFF website
Hi there people! I think most of this blog readers are familiar with half-wave antenna such as the 2 meter dipole I’ve built as a side project (with height about 1 meter by itself).
But do you know the height of the tallest and biggest half-wave antenna ever built in the world? is it 30 meters? 50 meters? 100 meters? Nope.. the answer is 646.38 m or 2,120.67 feet high when measured from its base on the ground.
Unlike other ordinary radio tower which is build to ensure you can put the antenna at the highest point, the Warsaw radio mast acts as a half-wave antenna itself!
It height 646.38 meter is the exact length of the frequency it was transmitting which is 225kHz, most probably using this formula
half-wavelength = 300/freq * 0.5 * velocity factor
= 300/0.225 * 0.5 * 0.97
= 646 meter.
As comparison, my homebrew half-wave antenna is only 0.996 meter in length, and is drastically dwarf by the Warsaw radio mast radiator.
Completed in 1974, the Warsaw radio mast transmit public broadcast radio station using 2 megawatts on 225kHz frequency. It was also the tallest structure in the world (recorded on Guinness Book of Records) until it finally collapse on 1991 due to maintenance crew failure.
Despite its collapse and inoperability for more than a decade. The Warsaw radio mast still remained the tallest/biggest (and the only longwave LF ) half-wave antenna ever build in the world,
Impressive isn’t it? Take a look at the antenna site in Wikimapia.
Read more about Warsaw Radio Mast in Wikipedia.
Short on a good and reliable antenna for your amateur radio operation ?
Here’s how to make a simple 2 meter amateur radio antenna from ordinary tv antenna (Rabbit Ears Antenna).
For your information these antenna can be bought from local tv store at around RM4 a piece (less than USD2).
The best thing about these antenna that it has terminating point (screw) which you can screw in your coax cable to each dipole leg, as shown in the (rather blurry) photo.
After that, extend the telescoping element to the desired length to match your transmitting frequency.
Usually amateur radio operator working on 2 meter VHF would use antenna with vertical polarisation. In this case, you need to spread the dipole to vertical position like pictured above, connect it to your transceiver and be amaze by its transmitting (or receiving) power.
Main Advantage of This Antenna
- Embarassingly easy to construct
- Can be adjusted to any frequency, because of its adjustable telescopic element
As you can see, the rabbit ear tv antenna can also make a good antenna during emergency situation. Its adjustable telescopic elements made it easy to reconfigure the antenna to transmit on different frequencies.
ps : You can use this dipole calculator, if you unsure about the dipole length.