I've decided to get into WSJT, and have been gradually putting together my
station. (I probably won't be on the air for the Sprint, though.) As setup
progresses, I've run into some interesting questions that I'd like to get
some opinions from the group.
* Icom IC-251 2M all mode
* MFJ-1275 Sound Card Interface
* IBM Thinkpad 600x (P3 500MHz)
* Arrow Antenna 4 element 2M beam (will go on temporary tower
at 25 ft later this week, rooftop mount coming later)
* Maha MH-A104 100 watt Linear Amp w/preamp (not yet integrated - that's
this weekend's project)
As of last night, I got my radio operating under the control of the PC, and
I started taking noise measurements off my 2M vertical antenna (the beam's
not up yet), with no preamp. I fed the headphone output to the internal
sound interface (Crystal audio), and for comparison, a pro-grade sound
interface PCMCIA card that I use for my home recording studio.
Representative WSJT 4.6.1 captures from each card can be seen at
which lead to a question for the
Note the severe shape of the bandpass -- there's a peak at 500 Hz and then
a pretty steady decline until the curve bottoms out around 2600 Hz.
(Obviously this is due to tone shaping to improve voice intelligibility.)
Question: will this have an impact on my ability to decode received data?
I'm especially concerned about how near the high frequency cutoff is to the
D tone marker. Anybody have any suggestions on how to deal with this?
I also note the difference in recording quality between the internal sound
card and the pro sound card, along with the extended high-end audio
Next question: I'm in a suburban area, with 1 and 2 story houses pretty
much in every direction, not very far away (a couple hundred feet). For
various reasons, a full-scale tower is probably out of the question, though
a rooftop mount is doable. I'm concerned about potential RF exposure issues
for people and houses in front of my beam. Any input on this? Also, what
impact will a house have on my signal if my beam is pointed at it? Would
tilting the beam up about 20 degrees make things any better?
I'm sure I'll have other questions as I go. I'd appreciate any input. With
luck, I'll be up from EM79 pretty soon.
...phil / w8sca
"For a list of all the ways technology has failed
to improve the quality of life, press 3."