WRT the 857D DSP. Yes, it is at audio frequencies. (So is a sound card). Still quite helpful both in rejecting signals as close as 50 Hz (depending on mode) and lowering broadband noise. At present my 857D is on an older KAM+ TNC that does not have PSK but I have used the 857D's DSP to help with TNC PSK in a crowded band and there is no reason it should not help with sound-card modes. (My FT-450's audio DSP notch mode helps with MT63 and Olivia in the presence of broadcast carriers.)
FWIW, I think the 857's optional filters are better than the 450's built-in IF DSP if only because you CAN use narrow filters in digital modes. The 450 only lets one go down to 1.8 KHz in digital mode which is not bad for MT-63 1 KHz or Olivia 1 KHz but not enough for the narrower modes. We are really spoiled by 10 Hz tuning steps. Sound cards can interpolate quite well. And even though the NTIA requires stability (IMO more important than frequency readout) of 10 Hz, that's over time and the manufacturers' rated temperature range. -10C to + 60C is NOT where I set the thermostat! Recent Amateur-grade rigs are enough after warm up in reasonably constant-temperature conditions and may not need a TCXO. I like them anyway.. Cortland KA5S > [Original Message] > From: Stelios Bounanos <[email protected]> > To: <[email protected]> > Date: 12/26/2009 6:27:34 PM > Subject: Re: [digitalradio] Need your help picking HF radio. > > >>>>> On Fri, 25 Dec 2009 11:07:39 -0700, Alan Wilson <[email protected]> said: > > > I'd have to go with the Yaesu ft-857D, it does it all with a small > > footprint, reasonable price and very dependable... > > I have one of those and I like it for many reasons, but it's not a very > good rig for digital modes. Some issues that come to mind: > > * DSP is at the audio stage, useless for digital. > > * Narrow IF filters (300 and 500 Hz) are extra. It can be frustrating > to operate on HF without one of these. > > * TCXO is extra (but standard with the FT-897D, IIRC). > > * Minimum tuning step is 10Hz. > > * Much CAT functionality is undocumented by Yaesu, though HB9DRV > and co. must have discovered all of it by now. > > * Reference oscillator is mounted behind the rear vent/heatsink and is > therefore in the draft of air from the cooling fans. Fans always > activate on transmit so you will drift, even for short transmissions > and with the TCXO installed, which is most annoying on VHF/UHF. > Can't blame Yaesu much about this though, it's a small rig. > > IMHO not worth considering for digital modes unless you _must_ have HF, > 2m and 70cm in a compact radio. But then something like the IC-7000 is > much better for that. And if you only want HF you have many more > options. > > > -- > > 73, Stelios, M0GLD. > > > ------------------------------------ =is subject to: > http://docs.yahoo.com/info/terms/
