Hi Ted, That's a good thought, but the problem is that achieving more than a 16 to 25 mile range without a repeater requires more gain (on at least one end - usually the home station end) than you can get from a lindenblad antenna, a big wheel, a ground plane, or even a 5/8 wavelength vertical. The portable end will also generally be at a lower elevation than the home stations. According to Cebik (http://www.cebik.com/ao/ao16a.html), the Lindenblad antenna has about 6 dBi of gain, and the big wheel about 7 dBi. Those antennas will work at the portable end, but on the home station end, more antenna gain (approximately 10 dBi or greater) is needed to ensure spanning a wide disaster area up to 100 miles without a repeater. For exceeding the distant obtainable by repeaters, which are usually positioned as high as possible, and usually higher than the typical home station antenna, even 3 dB of extra gain can make the difference between 100% copy and no copy. The Lindenblad is most useful for satellite work, where it can accomodate circular polarization and a high angle of reception.
For operators already using repeaters with FM-only transceivers, the move to SSB is the major change (i.e., a new transceiver!), and the antenna change to horizontal polarization is relatively minor. In many cases, where 5-element vertically polarized beams are being used to hit repeaters, it only involves fliping the beam 90 degrees. In fact, any such beam can also just be rotated 45 degrees and handle both vertical and horizontal polarizations, but with a 3 dB loss in gain for each polarization. There is a whole new world of fun available on 2m SSB and digital that those who only work VHF via repeaters are missing. Instead of collecting countries, VHF SSB stations collect grid squares, counties, and states, so there is quite a reward to be had for joining the horizontally-polarized VHF world on 2m as well as being ready to assist with emcomm. 2m SSB is not all "weak signal" operating. Using my 13 element 2m beam, I have consistently worked horizontally-polarized mobiles over distances just exceeding 100 miles, when the elevations of both myself and the mobile do not exceed 30 feet ASL. 73, Skip KH6TY ----- Original Message ----- From: Theodore A. Antanaitis To: digitalradio@yahoogroups.com Sent: Friday, February 29, 2008 4:16 PM Subject: Re: [digitalradio] Some thoughts on antenna polarization for emergency use How about the best of both worlds (or at least an approximation thereof). I would suggest for two meter home station applications that a lindenblad antenna is a versatile compromise omni-directional antenna that works equally well with both vertical and horizontal polarizations. The complexity of construction is not that much greater than for a big-wheel or three dipole array. One source for more info: http://www.amsat.org/amsat/articles/w6shp/lindy.html 73 Ted WA7ZZB > ------------------------------------------------------------------------------ No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.21.2/1304 - Release Date: 2/29/2008 8:18 AM
