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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.


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



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