The UHF amateur radio allocation extends from 430 to 440 MHz internationally, however, some countries, such as the United States, allocate hams 420 to 450 MHz. Technicians and higher class licensees have privileges across the entire 70 cm band, 420 to 450 MHz. The 70 cm band is BIG…providing 30 MHz of spectrum compared to only 4 MHz on 2 Meters.
The 70-centimeter or 440 MHz band is a portion of the UHF radio spectrum internationally allocated to amateur radio and amateur satellite use. This band is commonly referred to as the "70 centimeter" band because the wavelength at 440 MHz is approximately 70 centimeters. In the United States, the band extends from 420.0 to 450.0 MHz with geographical and power restrictions that may apply to all bands above 420 MHz.
Primary and Secondary Allocations
The band is shared with other radio services in the United States with government radar systems such as PAVE PAWS. Amateur operators are permitted to use up to 1500 Watts PEP maximum on VHF and higher bands. The FCC rules do not specify any mode restrictions on this band.
International vs US Band Plans
In the United States and Trinidad and Tobago, the band ranges from 420 to 450 MHz with some geographical limitations. In Canada and Australia, the band is 430–450 MHz. In the UK and Ireland amateurs are allocated 430–440 MHz.
By international treaty between the US and Canada, operation in the portion of the band from 420 to 430 MHz is prohibited north of Line A, which runs just south of the Canada–US border from Washington state to Maine, and east of Line C, which runs from northeast to southeast Alaska.
UHF Band Segments and Allocations
420-430 MHz Segment Breakdown
There is a restriction on operating below 430 MHz if you are close to the US border with Canada. This is the so-called Line A Restriction. Most hams will not be operating below 430 MHz unless they are using Amateur Television.
According to the ARRL band plan, the 420-430 MHz segment is primarily designated for Amateur Television (ATV) operations, including ATV repeater or simplex, control links, and experimental activities. This segment provides excellent bandwidth for fast-scan television transmissions.
430-440 MHz Frequency Uses
The 430-440 MHz segment contains several specialized sub-bands that support various weak signal and experimental applications. On the low end of the band, we see segments for some of the more exotic modes, starting with ATV, then Earth-Moon-Earth (EME) operation.
Key allocations in this segment include:
- 430.00-432.00 MHz: ATV simplex operations
- 432.00-432.07 MHz: EME (Earth-Moon-Earth) communications
- 432.07-432.08 MHz: Propagation beacons
- 432.08-432.10 MHz: Weak signal CW operations
- 432.100 MHz: SSB calling frequency
- 432.10-432.125 MHz: Mixed mode and weak signal operations
- 432.125-432.175 MHz: OSCAR satellite inputs
- 432.175-433.00 MHz: Mixed mode and weak signal operations
- 433.00-435.00 MHz: Auxiliary/repeater links
- 435.00-438.00 MHz: Satellite only operations
440-450 MHz Repeater Coordination
There are portions of the band designated for repeater inputs and outputs. The standard repeater offset used on this band is 5 MHz. On the UHF band (440–450 MHz), the standard offset is 5.000 MHz.
Some areas of the country use + 5 MHz offset while others use – 5 MHz. Within any region, the offset will be usually be the same on all repeaters. This means that in some parts of the country, you'll dial in the repeater output frequency in the range of 442 to 445 MHz and select a +5 MHz offset. In other areas, you'll dial in a repeater output frequency in the range of 447 to 450 MHz and select a -5 MHz offset.
Repeater outputs will always be between 440 and 445 MHz and always a plus offset (your radio transmits 445 to 449.975). The UHF offset is 5 MHz. However, regional variations exist, with repeaters on or above 445MHz typically using a - 5MHz offset and those below 445MHz using a + 5MHz offset for the standard offsets.
Weak Signal and Experimental Segments
The UHF band provides excellent opportunities for weak signal communications and experimental work. Narrow-band modes with a maximum bandwidth of 2.7 kHz are always located at the low frequency end of any VHF or UHF allocation. This is where you will find Morse (CW), telephony (SSB) and machine generated mode (MGM) activity such as JT65C and FSK441. In addition to the separate CW sub-band this is the area of the 432MHz band where operators make long-distance (DX) contacts.
FCC Regulations for UHF Operations
Power Limitations and Restrictions
Amateur stations must use the minimum transmitter power necessary to carry out the desired communications. No station may transmit with a transmitter power exceeding 1.5 kW PEP. For UHF operations specifically, technician licensees may use up to 1500 Watts PEP on the VHF and higher bands.
Geographical and power restrictions may apply to all bands above 420 MHz. For information about your area, see FCC 97.303 Frequency sharing requirements.
Bandwidth Requirements
Current FCC regulations specify different bandwidth limitations for various portions of the UHF band. In the 70 centimeter (420–450 MHz) bands, the specified digital codes may be used with a bandwidth not exceeding 100 kilohertz. The NPRM did not seek comment on eliminating the baud rate limit in the VHF or UHF bands allocated for amateur radio service.
Coordination Procedures
While the ARRL band plan sets the guidelines for band use across the US, VHF and UHF band plans are really defined on a statewide or regional basis. This means it is best to find the specific band plan for your region. The answer regarding coordination is going to vary based on local area coordinating council policy.
Local frequency coordination bodies manage repeater assignments and interference prevention. These areas sometimes use their own unique offsets, referred to as an 'odd split'. You could check your local coordinator's site to find out whether they're using a plus or minus offset.
Part 97 Compliance Requirements
It is good amateur practice to follow the band plan established by the Amateur Radio community. The band plan is developed so that spectrum allocated for our use is used most effectively. While band plans are not legally binding, they represent best practices for efficient spectrum utilization and interference prevention.
UHF Repeater Coordination and Planning
Repeater Frequency Pairs
FM operation is "channelized", meaning that specific 70 cm FM frequencies are identified by the band plan. The use of channels is especially important for repeaters, since they don't easily move around in frequency and are coordinated to minimize interference. The idea is to have all stations use frequencies that are spaced just far enough apart to accommodate the signal without interfering with the adjacent channels.
Most new radios default to 25 kHz channel steps, which is correct for Northern California UHF repeaters. However, Southern California UHF repeaters use 20 kHz channel spacing. If you're trying to land on a frequency like 448.060 MHz, you'll need to switch to 5 kHz or 20 kHz steps.
Input and Output Offsets
In most parts of the US, the standard offset is 5 MHz on the 70cm band, and can be either in the positive (+) or negative (-) direction. Your repeater directory will list the offset and direction.
In Colorado, the transmit offset on 440 MHz repeaters is – 5 MHz (that is, the repeater input frequency is 5 MHz below the output frequency.) However, it's +5 MHz below 446, above that it's - 5 MHz. 446.000MHz is the Call channel and is not paired.
Coordination Body Requirements
VHF/UHF band plans are managed regionally, so if you are not in Colorado check with your local repeater coordinating body. These organizations maintain databases of coordinated repeaters and manage interference resolution.
CTCSS tones may be assigned, and their use will be required, on 440, 902, 1240 MHz and above. A change was made in Policy 14.G requiring the mandatory assignment and use of CTCSS tones for repeaters operating on 440, 902, 1240 MHz, and above.
Interference Prevention Strategies
Proper coordination prevents interference between repeater systems and other users. The spacing between channels needs to account for the fact that a typical FM signal occupies a bandwidth that is about 16 kHz wide. This is why standard channel spacing is 25 kHz rather than the 5 kHz tuning steps common on most radios.
CTCSS stands for Continuous Tone Coded Squelch System. It is a sub-audible tone transmitted along with your voice signal that tells the repeater you are an authorized user. Without the correct tone, the repeater will not open up for you.
UHF Propagation Characteristics
Line-of-Sight Communication
70-centimeter propagation characteristics lie midway between 2-meter and 33-centimeter bands. Above 200 MHz, as frequency increases, building penetration is reduced. Smaller obstacles may also block or reflect the signal. However, higher frequencies also present a lower noise floor, making it easier to overcome both natural and artificial interference, especially prevalent in urban environments.
There is a misconception that VHF and up are line of sight only. This is incorrect. Only a modest setup is required to do 150+ miles any time day or night especially on the 144 MHz, 222MHz, and 432MHz bands.
Atmospheric Effects on UHF
Very often, in North Texas, the band will open up with enhanced propagation which allow even greater distances. Several times per year, it is possible to communicate from North Texas to Louisiana, Mississippi, Alabama, Georgia, and Florida. Once in a while, a massive opening occurs where contacts were made up toward all of New England.
Higher frequencies don't benefit from ionospheric effects, and generally don't propagate beyond direct line-of-sight. But in rare circumstances, atmospheric refraction can cause high-frequency radio signals to propagate much farther than normal.
Terrain and Building Impacts
A problem found with all UHF and higher frequencies is the prevalence of multipath signals. The reflective properties of the 70-centimeter band allow signals to be reflected by dense and solid material such as cement or rock. This creates a slight time delay between the primary and reflected signals, causing cancellations as direct and reflected signals are combined in the receiving antenna. This can cause receiving stations to experience rapid fluctuations in signal strength, or "picket fencing", when they are in motion.
Seasonal Propagation Variations
The amateur six metre (50 MHz) band sometimes provides intercontinental communication, while enhanced conditions on the higher bands (particularly during the summer) allows distances of thousands of kilometres to be covered. While 70 centimeters doesn't experience the same dramatic seasonal variations as lower frequencies, enhanced propagation conditions do occur more frequently during summer months.
Equipment and Antenna Considerations
UHF Transceiver Selection
Basic FM mobile or handheld transceivers usually tune the entire 70 cm band from 420 MHz to 450 MHz in 5 kHz steps. 70 centimeters is a popular ham band due to the ready availability of equipment in both new
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