Q. Revised
Section 97.303(h), says amateur stations may transmit on five specific center frequencies
in the 60 m band, Control operators of stations transmitting phone, data, and RTTY emissions (emission
designators 2K80J3E, 2K80J2D, and 60H0J2B, respectively) may set the carrier frequency 1.5 kHz below the center frequency.
For CW emission designator 150HA1A, the carrier frequency is set to the center frequency. What is
a carrier frequency?
A. It is an
artifact from when modulation technology was emerging. It can designate the nominal frequency of a carrier
wave; the center frequency of a frequency modulation (FM) signal; the frequency of the un-modulated electrical wave at the
output of an amplitude modulated (AM), frequency modulated or phase modulated (PM) transmitter; or the output of a transmitter
when the modulation is zero.
Our most
common understanding is, however, it is the number appearing on our transceiver’s frequency display. It
is the frequency with which our station’s transmitted signals are compared during the de-modulation process in a receiver.
In retrospect, the term reference frequency would have been a more meaningful choice.
Q. Is a carrier the radio signal that my station transmits?
A. Sometimes it is. It is a constituent, for example,
of a conventional AM transmission. AM is a method for transmitting information by varying the strength
of the transmitted signal in relation to the information being sent. The result is a carrier, along with
sideband signals on frequencies slightly above (upper sideband) and below (lower sideband), being transmitted.
Each sideband is a mirror image of the other and is equal in bandwidth to that of the modulating signal.
Q. What is
single sideband?
A. SSB is a
specialized type of AM transmission. One of the sidebands, along with the carrier, is suppressed during
transmission, leaving only the other – unsuppressed - sideband to be transmitted. The resulting signal
occupies considerably less bandwidth than if it was an unsuppressed full carrier double sideband AM signal.
To demodulate it for human hearing, the absent carrier is recreated within the receiver. The listener
simply adjusts this internal reference frequency until the voice reception sounds normal.
SSB is the predominant voice mode on our HF bands. On our 160, 75 and 40 meter bands, LSB is the
convention. On 20 meters and above, it is USB. For 60 meters, Section 97.307(f)(14)(i) mandates USB.
For the first half-century
of amateur radio, a cacaphony of our telephony reference frequency carrier signals were transmitted by our AM stations; for
the past half-century - gratefully - they have been replicated more calmly within our SSB receivers.
Q. Why is 60 meters limited to USB?
A. The
60 meter band is unique. It is not an amateur service band internationally. We are but
a semi-tolerated secondary user in places where the FCC regulates. Our arrangement package, therefore,
comes burdened with extensive technical and operational conditions - traditionally absent from our rules - ostensibly to decrease
the interference potential to the primary user stations.
Obviously, the primary users’ spectrum management practice is based upon a series
of 2.80 kHz wide channels, each of which is identified by the frequency at its exact center. Our tradition,
on the other hand, has been to identify by their carrier frequency our spontaneously self-selected channels. On-off
keyed CW is the only one of the four authorized modes where the primary user’s center frequency and our carrier frequency
coincide.
Q. What is the meaning of the term emission designator 2K80J3E?
A.
It is a narrow SSB-only voice transmission. Firstly, Section 2.201(g) says that whenever the full designation of a signal is necessary – and
it is in the instance of 60 meter sharing – the symbol shall be preceded by the necessary bandwidth of the emission
as indicated in Section 202(b)(1): The necessary bandwidth shall be expressed by three numerals
and one letter. The letter occupies the position of the decimal point and represents the unit of bandwidth. In
our case, therefore, it is 2.80 kHz.
Secondly, the symbol J indicates a single sideband suppressed carrier
emission in which the main carrier is amplitude-modulated. The symbol 3 indicates a single channel containing
analogue information. The symbol E indicates telephony. Read Section 2.201.
Section 97.307(f)(14)(i) further restricts us to USB.
Q. What are the meanings of the other three emission designators?
A.
CW emission designator 150HA1A means (A) double sideband emission in which the main carrier is amplitude-modulated;
(1) a single channel containing quantized or digital information without the use of a modulating sub-carrier, excluding time-division
multiplex; (A) telegraphy for aural reception. The necessary bandwidth is 150 Hz. Section 97.307(f)(14)(i) further restricts us to Morse telegraphy by means of on-off keying.
Section 97.3(c)(1) even further limits us to the international Morse code.
Data
emission designator 2K80J2D means (J) single sideband suppressed carrier emission in which the main carrier is amplitude-modulated;
(2) a single channel containing quantized or digital information with the use of a modulating sub-carrier, excluding time-division
multiplex; (D) data transmission, telemetry, telecommand. Section 97.307(f)(14)(i) further restricts us to USB (for example, PACTOR-III).
RTTY emission designator 60H0J2B means (J) single sideband suppressed carrier emission in which the main carrier is
amplitude-modulated; (2) a single channel containing quantized or digital information with the use of a modulating sub-carrier,
excluding time-division multiplex; (B) telegraphy for automatic reception. The necessary bandwidth is 60.0
Hz. Section 97.307(f)(14)(i) further restricts us to USB (for example, PSK31).
A sound card is a very useful feature of most of our personal computers.
It can convert our analogue audio into its digital counterpart for high speed processing and also can convert its digital
output into analogue audio compatible with our transceivers.
Three mini-phone jacks usually provide for simple pc-to-transceiver interconnection. The audio output
jack is labeled with an earphone icon. The other two are for input, one of which is labeled with a microphone
icon; the other is for higher voltage levels. Use the latter when you feed the audio from the earphone
jack on your transceiver. Even then, a resistance divider may be required to prevent overload.
Q. Ham RTTY is wider in bandwidth than 60 Hz. We use 170 Hz shift FSK, so the bandwidth
is at least that wide.
A. Section 97.307(f)(14)(i), however, restricts 60 meter RTTY to 60
Hz necessary bandwidth. In effect, that precludes 170 Hz shift FSK RTTY.
Q. What is the meaning of necessary bandwidth?
A.
Section 2.202(b) defines it as - for a given class of emission - the minimum value of the occupied
bandwidth sufficient to ensure the transmission of information at the rate and with the quality required for the system employed,
under specified conditions. Emissions useful for the good functioning of the receiving equipment as, for example, the emission
corresponding to the carrier of reduced carrier systems, shall be included in the necessary bandwidth.
Q. What, then, is occupied bandwidth?
A.
Section 2.202(a) defines it as the frequency bandwidth such that, below its lower and above its upper
frequency limits, the mean powers radiated are each equal to 0.5 percent of the total mean power radiated by a given emission.
In some cases, for example multichannel frequency-division systems, the percentage of 0.5 percent may lead to certain difficulties
in the practical application of the definitions of occupied and necessary bandwidth; in such cases a different percentage
may prove useful.
Q. What is PSK31?
A. Phase Shift Keying 31 Baud is
a RTTY modulation mode providing real-time keyboard-to-keyboard texting developed by G3PLX. It works well
at low power and does not require a large antenna. Several clever pc software programs – some free
– are available for downloading.
With your SSB transceiver connected to the sound card
of your pc, you keystroke your message for transmission. The software then produces an audio tone by switching
the polarity of the signal used to key your pc's sound card; binary information is transmitted by either
imparting a 180-degree polarity shift (binary zero) or no polarity shift (binary one) in each 32ms symbol interval.
For 60 meter transmissions, Section 97.307(f)(14)(i) restricts us to USB.
Q. What is PACTOR-III?
A. It is a data modulation
mode combining the bandwidth efficiency of packet radio with the error-correction and automatic repeat request of AMTOR.
Amateur radio operators were involved in developing these digital modes.
For 60 meter
transmissions, Section 97.307(f)(14)(i) restricts us to USB.
Q. Are we restricted to PACTOR-III? Can’t we use PACTOR-I or -II? PACTOR-III is not generated by insertion of
pc generated audio into a SSB transmitter; it requires an expensive proprietary modem. There are lower-cost alternatives.
Winmor is one such work-alike. It is a soundcard mode which I think may qualify as emission 2K80J2D. Its widest bandwidth
is 1600 Hz. Another is MT63. While it can be used keyboard-to-keyboard, it isn't "direct printing" because
it encodes blocks of characters or data at a time and adds FEC. Its widest bandwidth is 2000 Hz. It is most often used in
its 1000 Hz bandwidth setting.
A. The 60 M band emission requirements codified in Section 97.307(f)(14)(i) says, for the Data line item: emission designator 2K80J2D restricted
to USB (for example, PACTOR-III.) The emission designator is the operative rule; PACTOR-III is but an example.
Whether some other data modulation mode can be transmitted compliantly on 60 meters depends upon whether it is consistent
with emission designator 2K80J2D.
Q. Can CW be generated by my pc?
A. Yes it can,
but on 60 meters the transmitter must be on-off keyed. It must, moreover, be set to the channel center
frequency. Read Section 97.303(h).
Q. A bandwidth of 150 Hz will accommodate 37.5 WPM. Does that mean we can’t
send faster than that on 60 meters?
A.
Possibly, as the occupied bandwidth increases with telegraphy speed. So, if the resulting mean powers
radiated exceed 99% of the authorized 150 Hz necessary bandwidth, it is disallowed.
Q.
Does Data exclude what we call RTTY?
A. Yes.
In Part 97, the term Data is defined as telemetry, telecommand and computer communications
emissions having certain designators. Read Section 97.3(c)(2). The term RTTY is defined as narrow-band direct-printing
telegraphy emissions having certain designators. Read Section 97.3(c)(7).
Q. There is no USB and LSB for PSK. It is not FSK and it is not SSB, even though
we generate it with audio fed into our SSB transmitters. It can be copied with the receiver set to either USB or LSB.
It can be generated with your transmitter set to USB or LSB.
A.
USB is specified, evidentially, as the means to assuring that – with the transmitter set to a channel carrier
frequency authorized in Section 97.303(h) - the transmitted signal will more
or less be centered within the channel. Note in the rule where the specified carrier frequency is always
1.5 kHz lower than the specified center frequency.
Q. The table in Section 97.303(h) seems predicated upon the notion that Data and RTTY can be transmitted
as USB, probably because we sometimes generate them that way by putting an audio signal into a SSB transmitter.
But the result is FSK.
A. The 60 meter rules take some liberties in attempting to bridge the gap between our open architecture
customs and the wonderland of regulatory how-to-ism.
Q. We can’t tune up on 60 meters because A0 transmissions are not allowed.
A.
Actually, Section 97.305(b) authorizes a station to transmit a test emission on any frequency authorized to the control
operator for brief periods for experimental purposes. Section 97.3(c)(9) defines test as emissions containing
no information having the designators with N as the third symbol. Keep over-the-air tune-ups to a minimum and never on a channel where it would disrupt
other stations. Tune the transmitter into a non-radiating dummy antenna. Adjust an antenna
tuner using a very low power SWR analyzer or similar accessory. See BE Informed No. 30 OTA27.
December 22,
2011
Supersedes
all prior editions