sabato 23 settembre 2017

Simple 6 elements Yagi for 144 MHz

This is a simple 6 elements Yagi for 144 MHz, build in a few hours, with the design of DK7ZB who has a wonderful site with many VHF and UHF antennas.

This is the link:  DK7ZB SITE
In this site you can find the dimensions for the dipoles (reflectors, active, directors). You can find single antennas and stacks. I was looking for an antenna for restrected space.

The boom is 2 m;  impedence is 50 Ohm; gain is 9,3 dBd.
Easy to build; fast good result with no tuning and re-tuning.

Detail of the aluminium used:

- 1 square tube 16 mm X 16 mm, length 200 cm
- for the dipoles: 6 aluminium bars 15 mm x 2 mm, lenght 1 m
- the reflector has been extended to reach the right dimension (1026 mm)

73 de IZ3AYQ

domenica 20 agosto 2017

Mountain radio network - real time situation, 20 august 2017 at 9.50 GMT

Real time situation, 20 august 2017 - Station listening in 446093.75 MHz FM for security in Mountains; many stations are portable, in excursion. Some stations are in fixed positions, maybe Alpine refuge or home or any other position.
Amateurs also listen on 145250 FM, as secondary frequency.

73 Fabio IZ3AYQ

venerdì 30 giugno 2017

Simple dual band antenna for 145 - 431 MHz - Pattern study

Pattern study using the software "EZNEC"  V6 free by W7EL

Ideal situation (dipole in free space):

At  145 MHz; this is the classic diagram of an half wave dipole:

At 431 MHz; this is a diagram of a 3/2 lambda dipole in free space:

But if you put the dipole in vertical polarization, 3 meters from the ground you che see this:

For the half wave dipole at 145 MHz:

For the same dipole at 431 MHz:

In both case maximun gain in low in the horizon and, yes this antenna is not for DX, but it is a simple, cheap and usable antenna.

73 de IZ3AYQ

sabato 29 aprile 2017

4 m vertical antenna for 40 meters band

4 m vertical antenna for 40 meters band: a new antenna to test, easy to setup in portable mode. Made from an old CB antenna, "reused".

73 de IZ3AYQ