Receivers may have this bandwidth, but there are no generally available transmitters from the big manufacturers that I know of that allow this bandwidth.
While the op-amps may be linear to greater than 20 kHz, they must also be have a flat response curve. The ouputs may also be pretty linear as far as power output. The schematics I looked at showed only simple feedback circuitry that would have a very sloped response. More complicated feedback would be needed to insure flat response. Look at stereo receivers to see what is required for this. Look I'm not saying you can't roll your own. All I'm trying to point out is that there aren't any "off-the-shelf" HF transceivers you can just hook up to a sound card and that will support a 20 kHz transmit bandwidth, other than perhaps an SDR. Consequently, "experimenting" with this wide of a bandwidth is not going to be wide spread nor will it be a commonly accepted mode on HF for quite some time. Jim WA0LYK --- In digitalradio@yahoogroups.com, "John B. Stephensen" <[EMAIL PROTECTED]> wrote: > > In the 1980's and 1990's there were rigs that allowed switching the IF filters indepedently of turning on the BFO and had 5-6 kHz bandwidth AF amplifiers for decent shortwave broadcast reception. I haven't bought a commercially made rig since the new millenium but I've seen this feature mentioned in at least one data sheet. A 10-12 kHz bandwidth for SSB would have been unlikely in an amateur rig in the past but should become more common as DRM software requires a 12 kHz output for a soundcard. > > The current designs by KK7B (mini- and micro- T2 and R2) use NE5532 op amps, which are certainly linear to 20 kHz, and 2N3904 preamps. The 2N3904 has an Ft of 300 MHz and it was linear to at least 50 kHz in home-brew equipment that I have made with almost identical circuitry. These kits would require modification, but they are inexpensive. > > I'd say that the SDR-1000 is fairly well known now. > > 73, > > John > KD6OZH >
