EdmondLascaris: Created page with "= Icom IC-705 transmit on 15 metre band (21-21.45 MHz) = The Icom IC-705 is a versatile portable transceiver that covers a wide range of amateur radio bands. Specifically, it is designed to cover HF (High-Frequency) bands, VHF (Very High Frequency) bands, and UHF (Ultra High Frequency) bands. The 15-meter band, which spans from 21.0 MHz to 21.45 MHz, is within the HF range, so the Icom IC-705 can transmit and receive signals on the 15-meter band. This makes the IC-705..."

2023-10-20T13:05:25Z

Created page with "= Icom IC-705 transmit on 15 metre band (21-21.45 MHz) = The Icom IC-705 is a versatile portable transceiver that covers a wide range of amateur radio bands. Specifically, it is designed to cover HF (High-Frequency) bands, VHF (Very High Frequency) bands, and UHF (Ultra High Frequency) bands. The 15-meter band, which spans from 21.0 MHz to 21.45 MHz, is within the HF range, so the Icom IC-705 can transmit and receive signals on the 15-meter band. This makes the IC-705..."

New page

= Icom IC-705 transmit on 15 metre band (21-21.45 MHz) =

The Icom IC-705 is a versatile portable transceiver that covers a wide range of amateur radio bands. Specifically, it is designed to cover HF (High-Frequency) bands, VHF (Very High Frequency) bands, and UHF (Ultra High Frequency) bands. The 15-meter band, which spans from 21.0 MHz to 21.45 MHz, is within the HF range, so the Icom IC-705 can transmit and receive signals on the 15-meter band.

This makes the IC-705 suitable for various amateur radio operations, including contacts on the 15-meter band, provided that you have the necessary privileges and licenses to operate in that frequency range. Always ensure that you are operating within the legal frequency allocations for your region and have the appropriate amateur radio license or authorisation to use this equipment.

= 15m Centre-Fed Dipole Antenna =

A 15-meter center-fed dipole antenna is a popular choice for amateur radio operators who want to operate on the 15-meter band. Here are some of its key characteristics:

* '''Length''': A center-fed dipole antenna for the 15-meter band has a total length of approximately half the wavelength for this band. Since the wavelength on the 15-meter band is around 20 meters, the dipole would be about 10 meters long.

* '''Center Feed''': As the name suggests, it's center-fed, which means the antenna is fed with a coaxial cable at the center point. This arrangement is relatively simple and efficient.

* '''Balanced Antenna''': The center-fed dipole is a balanced antenna, which means that it is designed to work with balanced transmission lines like ladder line or open-wire feeders. However, it's often used with a balun to match the balanced antenna to an unbalanced coaxial feedline.

* '''Directionality''': A dipole antenna is typically omnidirectional, meaning it radiates and receives signals equally well in all directions perpendicular to the wire. However, the radiation pattern can be influenced by the height above the ground.

* '''Height Above Ground''': The performance of a center-fed dipole can be influenced by its height above the ground. Optimal heights vary, but a typical recommendation is to install it at least a quarter-wavelength above the ground (about 5 meters for the 15-meter band).

* '''Bandwidth''': Center-fed dipoles typically have a relatively wide bandwidth, making them effective for a specific amateur radio band (in this case, the 15-meter band) and often for closely neighboring bands.

* '''Installation''': The dipole is relatively easy to install, and many hams use it as a straightforward and effective antenna. It can be configured horizontally, sloping, or even as an inverted-V, depending on the available space and height limitations.

* '''Resonance''': For optimal performance, the dipole should be cut to the resonant frequency of the 15-meter band. This means it will work most efficiently around the 21.0 to 21.45 MHz range.

* '''SWR Adjustment''': A good dipole antenna should be designed and installed to keep the SWR (Standing Wave Ratio) within an acceptable range to ensure efficient power transfer and minimal reflected power.

* '''Gain''': While dipoles are not high-gain antennas, they provide a good compromise between gain and omnidirectional coverage. The gain increases as the dipole is raised higher above the ground.

Remember that the performance of any antenna is also influenced by local factors such as surroundings, obstructions, and other antenna systems nearby. To get the best performance from your 15-meter dipole, consider the specific installation location and configuration in your setup.

== Upper and Lower HF Bands ==
High-Frequency (HF) bands are defined by their frequency ranges, and they are used for long-distance radio communication, especially via skywave propagation. The HF bands are typically allocated for amateur radio, shortwave broadcasting, maritime and aeronautical communication, and military applications. The term "upper" and "lower" HF bands can be somewhat relative, but here's a general division:

'''Low HF Bands''':

The low HF bands include the frequency ranges from the lower HF bands up to approximately 20 meters (14 MHz). These bands are often used for medium to long-distance communications. They offer good reliability, especially during the day, with the exception of the 160-meter band.
Examples of low HF bands:
* 160 meters (1.8 - 2.0 MHz)
* 80 meters (3.5 - 4.0 MHz)
* 60 meters (5.3305 - 5.405 MHz) - in some regions
* 40 meters (7.0 - 7.3 MHz)
* 30 meters (10.100 - 10.150 MHz)
* 20 meters (14.0 - 14.350 MHz)

'''Upper HF Bands''':

The upper HF bands typically refer to the frequency ranges from 17 meters (18 MHz) and higher. These bands are often associated with improved propagation characteristics, especially for long-distance communication during the day.
Examples of upper HF bands:
* 17 meters (18.068 - 18.168 MHz)
* 15 meters (21.0 - 21.450 MHz)
* 12 meters (24.89 - 24.99 MHz)
* 10 meters (28.0 - 29.7 MHz)

Please note that the allocation of specific frequency ranges to these bands may vary slightly by region, as determined by international regulations. Additionally, the state of the ionosphere, solar activity, and local conditions can influence the performance of HF bands. Consequently, operators may need to adapt their choice of frequency bands based on these factors for effective long-distance communication.

= Layers of the Ionosphere and HF Frequencies =

The ionosphere is a region of the Earth's upper atmosphere that contains charged particles, primarily electrons and ions. It plays a crucial role in the propagation of radio waves, especially for high-frequency (HF) communications. The ionosphere is composed of several layers, each with distinct properties that can affect the propagation of radio signals, particularly on the upper HF bands. Here's an overview of the primary layers and their effects on upper HF frequencies:

'''D Layer:'''
* '''Altitude''': Approximately 30-50 kilometers above the Earth's surface.
* '''Effect on HF''': The D layer primarily absorbs radio waves, especially on the higher HF bands (e.g., 10 meters and above). This absorption becomes more pronounced at lower angles of incidence. As a result, signals on the upper HF bands experience significant attenuation during the daytime. The D layer tends to disappear at night, which allows signals to propagate more effectively on these bands.

'''E Layer (Es Layer - Sporadic E)''':
* '''Altitude''': Typically located around 90-120 kilometers above the Earth's surface.
* '''Effect on HF''': The E layer is often associated with sporadic ionization patches, which can enhance radio signal propagation on the upper HF bands, particularly from 10 meters (28 MHz) to 6 meters (50 MHz). During sporadic E events, signals can experience short-skip propagation, enabling communication over longer distances.

'''F Layer (F1 and F2)''':
* '''Altitude''': The F layer is divided into F1 and F2 layers, with the F2 layer being the most significant for HF communications. F2 can extend from approximately 200 to 500 kilometers above the Earth's surface.
* '''Effect on HF''': The F2 layer has the most significant impact on the upper HF frequencies, typically from 14 MHz and higher. The F2 layer is responsible for long-distance HF propagation, including global communications on the 20-meter (14 MHz) and 15-meter (21 MHz) bands. The presence of the F2 layer allows signals to be refracted and returned to the Earth's surface, enabling long-distance "skip" propagation.

The state of the ionosphere is dynamic and can vary with time of day, season, and solar activity. Solar radiation and geomagnetic conditions influence ionospheric properties. This variation can affect the maximum usable frequency (MUF) and the optimal bands for HF communication. Hams and radio operators often monitor ionospheric conditions and use propagation prediction tools to determine the most suitable frequency bands for communication at a given time and location.

Understanding ionospheric layers and their effects is essential for successful long-distance HF communications, especially on the upper HF bands. It allows operators to make informed decisions about band selection, antenna configuration, and power output to maximize signal reach and reliability.

== HF Bands Permitted by Amateur Foundation Licence ==
* 80m (3.5-3.7 MHz)
* 40m (7.0 - 7.3 MHz)
* 15m (21.0 - 21.45 MHz) - best for F1 and F2 long distance skip propagation during the day (Upper HF Frequency).

Communicating with Queensland School using HF - Revision history