6 MetersThe Mystery Band

by Marc C. Tarplee, Ph.D.

N4UFP

6 Meters: Rhetoric vs. Reality

• No one is on 6 meters– (I’ve made over 1900 QSO’s on 6 m since 1992)

• There is no DX on 6 meters– (I’ve worked 46 states and 38 countries on 3 continents)

• 6 meters is the TVI band– (I have never had a TVI complaint from my neighbors)

What makes 6 m interesting?

• A wide variety of operating modes is available• No band offers a wider range of propagation

phenomena than 6 m• Station equipment requirements are modest• Antenna experimentation is much easier on 6 m

than the HF bands

6 Meter Band Plan• 50.0-50.1 CW, beacons (beacon sub band = 50.060-50.080 MHz)

• 50.1-50.3 SSB, CW (SSB calling frequency = 50.125 MHz)

• 50.10-50.125 DX window

• 50.3-50.6 All modes

• 50.6-50.8 Nonvoice communications (digital calling frequency = 50.62 MHz)

• 50.8-51.0 Radio remote control (20-kHz channels)

• 51.0-51.1 Pacific DX window

• 51.12-51.48 Repeater inputs (19 channels, digital repeater inputs are 51.12-51.18 MHz)

• 51.62-51.98 Repeater outputs (19 channels, digital repeater outputs are 51.62-51.68 MHz)

• 52.0-52.48 Repeater inputs (except as noted; 23 channels)

• 52.02, 52.04 FM simplex

• 52.2 TEST PAIR (input)

• 52.5-52.98 Repeater output (except as noted; 23 channels)

• 52.525 Primary FM simplex

• 52.54 Secondary FM simplex

• 52.7 TEST PAIR (output)

• 53.0-53.48 Repeater inputs (except as noted; 19 channels)

• 53.0 Remote base FM simplex

• 53.02 Simplex

• 53.1, 53.2, 53.3, 53.4 Radio remote control

• 53.5-53.98 Repeater outputs (except as noted; 19 channels)

• 53.5, 53.6, 53.7, 53.8 Radio remote control

• 53.52, 53.9 Simplex

6 Meter Propagation

• Every type of propagation is possible on 6 m:– Line of Sight

– Tropospheric Propagation

– Sporadic E

– Meteor Scatter

– Auroral Scattering

– Transequatorial F

– Ionospheric F2

Line of Sight (LOS) and Tropospheric Propagation

• Line of Sight– LOS coverage is determined primarily by the height of the transmitting and

receiving antennas– For typical amateur 6 m stations LOS coverage is about 20 miles– LOS propagation is unaffected by solar conditions, time of day or the seasons

• Tropospheric Propagation– Variations in the humidity of the troposphere cause RF to be scattered over the

horizon. This is known as tropospheric scatter– Temperature inversions (warm dry air located above cool moist air) refract RF

in the VHF range back towards the earth. Temperature inversions occur daily in the middle latitudes at sunrise and sunset. Communications are possible over a ranges up to 600 miles

– Over the oceans, stable temperature inversions can create a duct, through which VHF can travel without significant loss up to 2500 miles

Tropospheric Scatter

Tropospheric Ducting

Sporadic E (ES)• Clouds of high density ionization form without warning in the ionosphere’s E layer

• ES is not dependent on solar activity. It may occur any time, but is most frequent between May and August, with a smaller peak of activity in December

• Single hop ES has a range of ~1400 mi

• Double hop ES has a range of ~ 2500 mi

• Cause of Sporadic E is not known: high altitude wind shear may be responsible.

Sporadic E (ES)The ionized clouds that cause sporadic E propagation can move. This animated sequence shows grid squares contacted in ½ hour intervals during an ES opening beginning at 0500 Z, 10 June 2001

Meteor Scatter• As meteors are vaporized in the upper atmosphere, they leave behind ionized

trails at heights of 60 – 70 miles that are sufficiently dense to reflect VHF

• A long trail lasts only 15 seconds so contact must be made quickly on SSB

• SSB QSO’s via meteor scatter are usually possible only during a meteor storm

• Short trails that occur continuously may be used for high speed CW QSO’s (> 100 wpm)

• Best time for meteor scatter is after midnight or during a meteor storm

Aurora (Au)• During periods of intense

auroral activity, charged particles in the auroral zone can scatter 50 MHz RF

• The RF interacts strongly with the aurora, resulting in significant distortion of the signal. Only narrow band modes such as CW are used during Au openings

• To work Au, the transmitter and receiver point their antennas at the auroral zone,

not each other.

Transequatorial F (TE)

• The ionosphere’s F layer is most intense in the region of the geomagnetic equator.

• Stations within about 2500 miles of the geomagnetic equator can launch 50 MHz RF into these regions. The RF is refracted and travels across the equator and into the other hemisphere without scattering from the ground

• Stations using TE must be at approximately equal distances from the geomagnetic equator

F2 propagation

• Communications over long distances (> 2000 miles) are possible on 6 m via the F2 layer of the ionosphere during periods of high solar activity (solar flux above 220)

• Openings generally occur in spring and fall during daylight hours (similar to 10 m)

Propagation Example2001 June VHF QSO Party 6 m QSO’s

Traditional 6m Operating Modes• CW

– Used primarily below 50.100 MHz

– Used during auroral openings – narrowband modes like CW are less susceptible to distortion

• HSCW– CW sent at high speeds (200 wpm or more)

– Used with meteor scatter propagation

– Most operation takes place near 50.300 MHz

• SSB– Most common 6m mode - USB is the standard

– Calling frequency is 50.125 MHz

– 50.100 – 50.125 MHz is the DX window

Digital 6m Operating Modes• FSK441

– Uses triplets of 4 tones to transmit data • 882, 1323, 1764, 2205 Hz• Each character is sent as a 3 tone sequence• 43 Character alphabet (letters, numbers . , / ? # $ <sp>)• Single tone characters used for shorthand messages:

– 882 Hz - R26 1764 Hz - RRR– 1323 Hz – R27 2205 Hz - 73

• Data rate = 147 characters per second (3 tones/char)• Used for meteor scatter communications• Most activity takes place near 50.270 MHz• Messages sent in 30 sec intervals – westernmost station

transmits during first 30 seconds of each minute.

Digital 6m Operating Modes• JT65B

– Narrowband PSK• 64-ary PSK (6 bits per baud)

• ~2.7 Baud signaling speed

• ~5.4 Hz operating bandwidth

• Requires a stable receiver, good timing• Messages sent in 60 sec intervals – westernmost station

transmits during even-numbered minutes.• Provides clear copy at SNR < 0 dB• Used for moonbounce and troposcatter operation• Most activity takes place near 50.270 MHz

6 Meter Station Requirements• Transceiver or Transverter

– RF output of at least 10 W PEP (>100W for FSK441, JT65, ~1000W for EME) with multi-mode capability (CW/SSB/FM)

• ICOM 706, 746, 756• Yaesu FT-100, 817, 847, 920• Kenwood TS-570• Alinco DX-70TH

• Antenna– Gain of at least 5 dBd (> 15dBd for EME)– Should be rotatable (az-el rotation is very important for EME)– Should be at least 20 ft above ground– Use low loss coax (RG8 up to 75 ft, Belden 9913 for longer runs)

• Useful accessories– RF pre-amp (RF switched)– Grid Square Map– PC (for FSK441, JT65)

6 Meter Antennas

• 6 m antennas are relatively small, light and easily rotatable.• Best choices for a new operator:

– 2 element quad– 3 element Yagi– Extended Double Zepp– 6/10 dual band dipole

• For weak signal work (CW/SSB) the antenna should be horizontally polarized

• For repeater operation, vertical polarization is the norm• For EME an array of 4 long yagis is typical• Meteor scatter operation requires an antenna with good gain and

broad beamwidth – 5 to 9 element yagis work well.

6 Meter Quad and Yagi Antennas• 2 element Quad (square loops of #14 ins. wire Z ~ 60 ohms Gain ~ 4 dBd)

– Element Loop Length (in) Position (in)– Reflector 245.0 0– Driver 235.5 29

• 3 element Yagi (Aluminum tubing Z ~ 42 ohms gain ~ 5 dBd)– Element Half Length (in) (0.75 dia 0.625 dia) Position (in)– Reflector 24 35.875 0 – Driver 24 31.875 50– Director 24 26.375 87

• 5 element Yagi (Aluminum tubing Feed Z ~ 35 ohms Gain ~ 8 dBd)– Element Half Length (in) (0.75 dia 0.625 dia) Position (in)– Reflector 24 35.875 0– Driver 24 33.875 49– Director 1 24 30.000 72– Director 2 24 29.500 121– Director 3 24 28.000 169

Other 6 Meter Antennas

• Dipole – Length = 114 inches (#14 wire) Z ~ 70 ohms Gain ~ 0 dBd

• Extended Double Zepp– Length = 282 inches (#14 wire) Z ~ 45 ohms Gain ~ 4 dbd

– Antenna is fed at the center through a 39.25 inch length of 450 ohm ladder line (VF = 0.9)

• 6/10 dual band dipole– Length = 198 inches (#14 wire) Z ~ 64 ohms Gain ~ 1 dBd

– Antenna is fed at the center through 32 feet 4 inches of 450 ohm ladder line (VF = 0.9)

– Antenna also can be used on 10 meters (Z ~ 72 ohms)

6 Meter Activities

• Contests– ARRL January VHF Sweepstakes (3rd weekend in January)– ARRL June VHF QSO Party (2nd weekend in June)– SMIRK QSO Party (3rd weekend in June– CQ WW VHF Contest (2nd weekend in July)– Six Club 6 m Sprint (3rd weekend in July)– ARRL September QSO Party (2nd weekend in September)

• Operating Awards– VUCC – contacts with 100 Grid Squares, not difficult– WAS – tough, but not impossible– DXCC – very tough from North America, but it has been done

• Grid Square Hunting– There are over 500 grid squares in the continental US– No one has worked them all yet (except perhaps for W5FF)

What is a Grid Square?

• Almost all VHF operating awards and contests involve grid squares

• Grid Squares are 2º longitude x 1º latitude sections of the earth’s surface (there are 32,400 in total)

• Each grid square has a 4 character designator containing 2 letters and 2 numbers. – The two letters designate the field. There are 324 fields lettered AA

through RR

– Each field is divided into 100 squares numbered 00 through 99

• The continental US includes grid squares in fields CM,CN, DL, DM, DN, EL,EM,EN, FM and FN

• Most of Rock Hill is in grid square EM94.

World Grid Fields

Grid Square Map of the USA