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TECHNICIAN
BAND EDGES! WATCH OUT!
YOU MAY
FALL OVER THE CLIFF INTO THE HANDS OF THE FCC!
Watch
those Band Edges!
Look at your frequency readout or you may have a
"Close Encounter" of the worst kind.....with Uncle
Sam!
by Don Butler,
N4UJW
As the year 2010 rolls around,
activity on the 10 meter band is gradually increasing with the new solar
cycle and many Tech class operators are stomping at the bits to get some
DX.
You just fired up your rig and the 10 meter band is really
hopping. Mother nature is being very kind to you one day while
you are on 10 meters and you hear a really cool DX station on
28.497Mhz USB mode with a good signal.
In your excitement, you know
that as a Tech class operator you're allowed to operate voice
(SSB) from 28.300Mhz up to 28.500Mhz.....so you say to yourself, that
is within my band privileges. Whoopie! I have got to get him while the
band is hot! I'm going to go for it and add another QSL card to my limited
numbers and confirm him as another DX entry in my log. I feel sure
he should hear me!
You tune his voice precisely to
normal sounding on exactly 28.497Mhz on your frequency readout. He is
showing S 9 plus on your S meter. You check that your radio is ready
to transmit and you give him your call sign in hopes that he will
hear you....you unkey and wait............................
(But you may be waiting for a close encounter with the FCC
rules for being out of band!)
WHAT? You say...... "I am
transmitting on 28.497Mhz! That's not
higher than 28.500Mhz which is my band edge!" How can I be out of
band?
Well my dear ham friend, here
is why you may be "OUT OF BAND".
When in SSB
mode, most transceivers display the frequency of the suppressed carrier.
(Your VFO readout frequency).This can be a bit confusing,
because with good carrier suppression, your
station isn't emitting any energy at all on that
frequency.
All of your transmitter power is going into the
voice passband that extends
roughly from 300 to 3000 Hz on one side or the other of that
(carrier) frequency depending on which side band your on. Your
transmitting on USB on 28.497Mhz, meaning that the voice energy
(power) of your signal is being transmitted "upper side band" which
corresponds to "higher" than your "carrier" frequency of 28.497Mhz that is
displayed on your frequency readout. So, the energy of your voice and
especially the higher pitched portions of your voice may
actually be extending up (higher) in frequency from 28.497Mhz towards
or higher than the band edge. But the problem is that you don't know
how far beyond (higher in frequency) your voice frequencies
are actually being transmitted so you may actually be transmitting a
portion of your signal.....out of band!
If only a very
tiny portion of that power is
higher in frequency than 3000 Hz, which would take your signal higher than
the "edge of the band", then...
guess what...you're
OUT OF BAND and the "Close
Encounter" with the FCC could very well happen! You must have NO
portion of your fundamental frequency signal out of band to be
safe!
All it takes to be out of
band is for the letter "S" or other high pitched syllable of your
voice to go beyond 3000 Hz, and your in trouble and breaking a very
important rule of the FCC...Part 97! (FCC Part §97.307 Emission standards)
The bottom edge of the US phone band for Amateur
Technician class license holders is 28.300Mhz. Without getting
into splitting hairs with a microscope about how wide your SSB
signal might be compared to others, if you're operating on lower sideband
(LSB) with a carrier frequency (your VFO frequency), below 28.297Mhz you're most likely out of
the voice band because some of your transmitter power may be below
28.300Mhz. If the highest pitch audio frequency of your voice is
higher in an audio frequency more than 3000Hz, the math does not
lie...you are out of the voice
band!
At the top edge of the 10 meter
band, 28.500Mhz, as long as you're on
LSB the situation is different; if you're confident that
your opposite sideband (USB), and carrier suppression are up to
snuff, you can snuggle up to the band edge of 28.500Mhz on LSB ONLY, but to be really safe....don't balance your foot on that
cliff edge with your VFO...your transmitter could be faulty without your
knowing it! Over that cliff you go!
Remember, you can be usually safe using LSB mode on the high
end of the band very close to the band edge, but not on the low end of the
voice portion and vise versa for USB mode
operation.
Example:
So where should I set my VFO?
LSB ON HIGH END ONLY
TO BE SAFE. 28.496Mhz (This gives you 4Khz away from the band
edge)
USB ON LOW END ONLY TO BE SAFE. 28.304Mhz (This gives
you 4Khz away from the band edge.)
(These are only suggestions to be
safe)
Always have about 4Khz from each of the band edges
displayed on your VFO regardless of which sideband you are
using.
Most hams
do not have the needed test equipment or measure their carrier
suppression and sideband width when they are on the air! Do you? I
thought so!
So what can you do to help
prevent going "out of band" on the upper end of your 10 meter band
privileges?
Instead of going
all the way to 28.497Mhz, just set your VFO readout frequency to not
higher than 28.496Mhz USB! Don't attempt a contact at higher than that
frequency. Simple as that....As long as your transmitter is within mfg's
specs, you should be safe. See chart below!
Suggested upper and lower frequency
limits for Tech class operators
Note that the green area of the
chart above designates a "safe" zone.
By following this simple suggestion of limiting
your station to an upper and lower frequency LIMIT within the SSB
voice portion of the band, you can be assured that in most cases assuming
your transmitter is working properly, that you won't be in violation of
out of band operation!
Now go after that DX station that is operating
within the "safe zone". Don't be tempted to go "just a bit further" just
to get another contact. Be safe, not sorry!
Good luck with your 10
meter fun and happy DX!
NOTE: The "standard" and
internationally used and accepted mode on 10 meters is USB, NOT LSB. Please refrain from using LSB ON 10
METERS!
When you upgrade to the General
or the Extra license class, similar rules apply to your
band edges.
On 160, 75/80, and 40 meters, use LSB.
60 meters, USB.
All bands from and including 20 meters and higher frequency bands, use
USB.
Remember, watch that VFO frequency or the FCC
will see you fall down over that cliff and be waiting for you at the
bottom!
More good
information on SSB. What is SSB?
73, Don N4UJW Hamuniverse.com |
