I agree, and there are modfications shown on web sites for DRM software. In my case, I have home-brew radios so I can easily support wide bandwidths. Since I've got code to transmt and receive OFDM using FPGAs I should modify it for narrower subcarrier spacings and do wideband HF OFDM some day.
73, John KD6OZH ----- Original Message ----- From: expeditionradio To: digitalradio@yahoogroups.com Sent: Thursday, May 03, 2007 22:22 UTC Subject: [digitalradio] Re: Wider Digital Bandwidth Filters - Hardware Mods > John kd6ozh wrote: > For 20 kHz bandwidths you'd need a software-defined radio > like the SDR-1000 or Soft Rock 40 where all the signal > processing is done in the PC. The T2 and R2 radios described > in QST 10 years ago would also be ideal for this use as > the audio filters can easily be widened. Hi John, It isn't necessary to use an SDR. You can modify a standard hardware transceiver with wide bandwidth filters. It is simple. Obtain a new wide bandwidth filter of the proper bandwidth and frequency, such as 25kHz bandwidth or 250kHz bandwidth. Install it in one of the filter options, or remove the original filter and install the new one. Other types of switching can be used as well. For transmit, tap into the balanced modulator directly with a high value series resistor, and run this directly to a shielded cable to an add a jack on the radio for it. This connects to the soundcard speaker output. For receive, add a small high impedance amplifier on a rider board inside the radio, and use a high value series resistor tapped into the product detector. Run this directly to a shielded cable to an add a jack on the radio for it. This connects to the line input of the soundcard. Bonnie KQ6XA
