DuBose Walt Civ AETC CONS/LGCA wrote: > Jose, > > This is what I have been saying for a couple of years now.
Se we are not alone. > Research done by "independent research laboratories and universities" > confirm that the best bet to increase throughput and robustness on HF > channel modems is to use parallel tone modems. I just cite the examples I have seen. DVB, DRM, IBOC, WiMax, etc, etc I have another non ionospheric related example: Wavelength Division Multiplex (WDM) on fiber optic links. Optical fibers do not not suffer from doppler, but do suffer dispersion and ISI. > I believe that the Russian modem you speak of is their 96 parallel > tone modem...but it requires more than 3-4 KHz of bandwidth. 93 tones with a pilot on 3.1 kHz. But there is enough bandwidth for it to pass thru a russian 500 kHz, 3.1 kHz wide mechanical filter with some carrier frequency tweaking on the radio...or using a software defined radio. It would be curious to know how that green box is built... 73, Jose __________________________________________ XIII Convención Científica de Ingeniería y Arquitectura 28/noviembre al 1/diciembre de 2006 Cujae, Ciudad de la Habana, Cuba http://www.cujae.edu.cu/eventos/convencion
