[ARC5] BC-221-WWV-sound card

[Bill Cromwell]

Hi Roy,

I think I have answered most of the questions here. Some of my comments 
are made with new people in mind...new people who arrive here using an 
archive search some time in the future. I may have assumed too much on 
the part of readers. By putting this in a post that may become a thread 
that can help other people along the line. Don't be offended if some of 
the comments explain things you already know nor if there are still any 
questions (from any of the list). I can easily mis-state something or 
miss the mark of being clear.

That iSpectrum software seems similar to Spectran. The two programs I 
use - Spectran and SpecLab - pipe the audio to the sound system 
speakers. That is really helpful when we first start (and useful on the 
air, too) and we have to identify WWV's carrier among the pips on the 
display.

I run audio directly from my receiver earphone jack to the line-in jack 
(or mic jack) on the sound card. I have to keep the receiver volume well 
down to avoid overloading the sound card. "Interfaces" usually have an 
isolation transformer and some sort of "level" control in the interface. 
I have been running without one but I will need one soon to be serious 
about transmitting with fldigi. fldigi is a good, all around, digital 
mode package for hams.

When we 'zero beat' signals by ear with a receiver and WWV (or a net 
control station) we can't hear all the way down to zero Hz. The receiver 
passband usually won't allow that even if our hearing response will (it 
won't). Even use of an Oscope doesn't help if the receiver is not 
passing those lowest tones. We can be a few cps (cycles per second for 
the Hertzian people) off. We can make estimates about where the 
decreasing beat not disappears on one side and reappears on the other 
and split the difference. That will narrow the error but no way to 
*know* how far off. Matching tones by ear isn't any better but an Oscope 
might be more helpful (and maybe not). A spectrum analyzer is more useful.

When you get iSpectrum up and running make a connector cable and pipe 
your receive audio into it. Play with it. Unlike the waterfall display 
the pips in the spectrum display are not vertical lines. They more 
resemble the ^ character and the height of the pip is proportional to 
the signal strength (at the sound card input). If no part of the system 
is overloaded the height of the pip is proportional to the strength of 
the signal at the receiver antenna (discounting RX agc).

When you have WWV on the screen (BFO on - either sideband) and the 
carrier is zero beat with your BFO so that you hear only the tones and 
the voice announcements the carrier will be all the way to the left side 
of the display. Arranged along the width of the display will be the 
ticks and the 440 Hz and/or 1200 Hz tones. The area at the left of the 
display where the carrier is - at zero - is useless. tune your radio to 
bring the carrier away from zero to some handy place on the screen. 
Everything will shift left or right as you tune the receiver. Tune the 
RX so the carrier moves moves to the right into the useful part of the 
display. 1 kc is a good area. You will be able to see AND hear the 
carrier as it moves up in frequency (at the soundcard input). So you 
have the WWV carrier positively identified on your screen.

Turn on your xtal calibrator (if you have one). It may or may not be 
dead on the WWV carrier. To be useful it should be pretty darn close. If 
your cal xtal is 1 mc (1 MHz for those who use them) then you are seeing 
any error of the xtal frequency multiplied by 10 (10 mc WWV) or 15 (15 
mc WWV). Small errors will show up as a dancing, wriggling moire pattern 
on one or the other slope of the WWV carrier pip. If you have the covers 
off and the mallet and chisel handy you could adjust your receiver's 
marker closer. Maybe the mallet and chisel are overkill and a small 
screwdriver more appropriate <evil grin>.

Turn off the marker, whether or not you have adjusted it. Use your 
signal generator (hopefully every ham has one) and put signals into your 
receiver with it near WWV. Move the new carrier closer and further from 
WWV and observe how the new signal moves up one slope, peaks at the top 
with no moire pattern and then down the other slope and finally away 
from WWV's carrier. You can also retune your RX to one of the ham bands 
and use the spot function on one of your transmitters to observe how 
iSpectrum or Spectran an help you get your TX netted with other signals. 
Many 'modern' hams don't have a TX that can do this.

Finally, warm up your LM or 221 and couple the marker into your receiver 
with WWV tuned as above. Tweak the marker xtal in the LM as needed to 
get it's signal at the peak of the WWV carrier pip with no dancing, 
moire, wriggling, nor squirming. You can observe for a while to watch 
for drift from the LM xtal marker or put the tools away for another day.

The above procedure should work for *ANY* spectrum analyzer. With an rf 
spectrum analyzer you could observe the carrier from WWV without a 'BFO' 
(maybe). The BFO is replaced by the swept oscillator in the RF spectrum 
analyzer. With the audio spectrum analyzer so easily available with our 
computer sound cards we have the same thing. Audio spectrum 
analyzer/sound card = *free*. RF spectrum analyzer = kilo$.

73,

Bill  KU8H