Dave, The 'Unun' theory is well known and used, but to my knowledge, not usually on long Verticals - In this case an effective length of 75 feet high, the way I have wound the vertical 75ft wire spirally around the 36 ft pole.
The construction of long-wire antennas with a Unun is simple, both electrically and mechanically, with no critical dimensions or adjustments. When using a Unun, a 9:1 will match 450 Ohms to 50 Ohms, a 6:1 will match 300 to 50 Ohms, a 5:1 will match 250 to 50 Ohms and a 4:1 will match 200 to 50 Ohms. The long-wire antenna using a Unun will work well and give satisfactory gain and directivity over a frequency range up to twice the value for which it was cut. In addition, it will accept power and radiate it efficiently on any frequency for which its overall length is not less than 1/2 wavelength. Mine is worse than useless on 80 and 160! My main inspiration came from this little article... http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php <http://www.m0ukd.com/Magnetic_Long_Wire_UnUn/index.php%20> Sorry to travel so far 'Off Topic' on the Group, I started this as a response to posts on long distance or DX Digital contacts during this current propogation 'Low' Topic. However, I feel sure that the subject is close to many amateurs list of favorite topics. Also - It is a 'Time-Served' privilege for those of us over 75 to 'Ramble on' - without any idea what we are talking about! 73's de John (G3OBU) http://www.John4Music.TV <http://www.John4Music.TV> ........................................................................\ ........................................... --- In digitalradio@yahoogroups.com, Dave Ackrill <dave.g0...@...> wrote: > > obrienaj wrote: > > John, > > > > I read with interest your web pages describing your vertical antenna. Please keep us informed on how it does on digital mode DX. I had to look twice at what I thought was a balun at first. > > I realise that we will probably be off topic, but a 9:1 UnUn is often > used in random length wire antennas for frequencies under about 1MHz. > > There are often various arguments for and against the 9:1 UnUn, some > people preferring the 4:1 version and others saying the 4:1 doesn't work > well for them. > > A quick google for '9:1 UnUn' will give quite a number of sites with > designs and arguments about what type of earth connection/wire/antenna > to use it with. > > Dave (G0DJA) >
