On Nov 10, 2009, at 10:20 PM, Scott Miller wrote: >> I have the newest T2 (with MX614). Is the schematic available yet, or >> changes to the manual? Also, when setting up the deviation, the best > > I just posted a preliminary version of the schematic to the files > section of the group. I've got a printed copy at the office with > all of > my changes to the output filter scribbled in, and I've got to look > those up.
Yes, thanks. It is very dim (low contrast), but readable on-screen. It is not readable when I try to print, even after adjusting the contrast in Gimp. I'll wait for your official schematic. > > I'm pretty sure C3 and C17 are 0.047 uF, R23 and R24 are 1k, R3 is 0, > and R35 is somewhere around 30k. I did not check these values before setting up in the car. Next time the T2 is out of the car I will. > > There won't be more than a paragraph or so added to the manual for the > new version, just an explanation of the two added solder jumpers and > other minor changes. > >> I can get is about 1.4kc with the HI jumper on. With the HI jumper >> off, I get no deviation at all. Also, it appears that the Transmit > > I *think* I got all of the output filters changed before anything > shipped, but check yours against my notes above. You should be able > to > get way more output from the new board than the old one, and with a > cleaner sine wave. > >> Audio Control has no "control" over the deviation - I see no change >> from min to max setting. Is that normal? (Hence, need for a >> schematic). > OK, again did not look at the TX out waveform. Will do when I have it out of the car again. > No, you should still get control just like before. Try it from the > command line - run CAL A and use [ and ] to change the audio level. > >> On a positive note, with the MX614, the Low tone is slightly lower in >> deviation than the High tone - unlike the OT+. I am feeding the data > > Actually that's just the new output filter. The MX614 is NOT used on > the output side, to maintain software compatibility and allow 300 baud > and PSK31. I understand your desire to be a do-all device, Scott. But, I think you would be better served in the APRS world to use the MX614 as your TX Audio producer, too. > >> port of an FT-1500. I probably need to wire up the MIC port to get >> more gain, maybe, and pre-emphasis. > > You should be able to get at least 800 mV p-p into a 600 ohm load. I did take a look at the specs for the FT-1500 data port. To get the recommended deviation of 2.75kc, the Tx audio needs to be about 1vp- p. That may explain why the 0.8vp-p from the OT+/2 is not giving me the desired deviation. I did revisit that issue. I can get the deviation to drop off when the control is set very near min. But, it immediately ramps up to "full deviation (1.35 to 1.45kc)" about 1/4 of the control beyond min position. When I get some time, I will wire-up and try the MIC input to the radio. 73 - Dale. KG5LT
