An astronomical object is Ascending when it is moving north in latitude with respect to the celestial sphere or "up" with respect to the usual ground map. Descending means moving south or "down" with respect to the map.

Last edited by rwbonnerjr. Register to edit

Tags: arrl chapter 2 arrl module 2b

The best way to remember this is to think of a map. Normally maps are held with north on top, so going "down" on the map is going from north to south.

Last edited by kk4uwv. Register to edit

Tags: arrl chapter 2 arrl module 2b

The definition of the word period in this case is a round of time marked by the recurrence of some phenomenon or occupied by some recurring process or action.

So, the "orbital period" is a round of time marked by the recurrence of the orbit of an earth satellite -- in other words, it's the time it takes for a satellite to complete one revolution around the Earth.

Last edited by kd7bbc. Register to edit

Tags: arrl chapter 2 arrl module 2b

Historically OSCAR uplink (transmit to) and downlink (receive from) frequencies were designated using single letter codes.

Mode A: 2 m uplink / 10 m downlink

Mode B: 70 cm uplink / 2 m downlink

Mode J: 2 m uplink / 70 cm downlink

New uplink and downlink designations use sets of paired letters following the structure X/Y where X is the uplink band and Y is the downlink band.

Reference: http://en.wikipedia.org/wiki/OSCAR#Mode_designators

Last edited by qubit. Register to edit

Tags: arrl chapter 2 arrl module 2b

Historically OSCAR uplink (transmit to) and downlink (receive from) frequencies were designated using single letter codes.

• Mode A: 2 m uplink / 10 m downlink
• Mode B: 70 cm uplink / 2 m downlink
• Mode J: 2 m uplink / 70 cm downlink

New uplink and downlink designations use sets of paired letters following the structure X/Y where X is the uplink band and Y is the downlink band.

Reference: http://en.wikipedia.org/wiki/OSCAR#Mode_designators

Last edited by rjstone. Register to edit

Tags: arrl chapter 2 arrl module 2b

The paired letters U/V indicate the uplink (receive) and downlink (transmit) bands that the satellite uses, where:

• U - 70 cm (in the UHF range)
• V - 2 m (in the VHF range)

See Wikipedia's page on amateur radio satellite a complete list of mode designators.

The order is uplink/downlink, which from the perspective of the satellite is receive/transmit.

Last edited by glitteribbon. Register to edit

Tags: arrl chapter 2 arrl module 2b

A linear transponder takes one range of frequencies and directly shifts it to another range, without decoding and re-encoding the signals. Therefore, any signal type that fits in the transponder's bandwidth can be used through it.

Last edited by ka0s. Register to edit

Tags: arrl chapter 2 arrl module 2b

Satellite transponders are power-sharing. If one signal received at the satellite is stronger than the others, all other retransmitted signals will get a smaller portion of the available power.

Last edited by marvsherman419. Register to edit

Tags: arrl chapter 2 arrl module 2b

Transponder link designators:

-w3mit

Study Hint: Think "(L)ittle and (S)mall" for 23 and 13 cm. “LS” looks like 23 and "ls" looks like 13.

See the mode designator chart

Last edited by ironcal67. Register to edit

Tags: arrl chapter 2 arrl module 2b

Many amateur radio satellites are spinning either as a form of stabilization or because of reduced ability to control attitude due to their small size and power budget compared to larger commercial satellites. When the satellite's antenna is spinning relative to a fixed ground antenna, fading can occur.

Last edited by ka0s. Register to edit

Tags: arrl chapter 2 arrl module 2b

Faraday rotation is the change in radio wave polarization due to the presence of a magnetic field, while spin modulation is also a polarization change, but due to the rotation of the signal source or of an object that reflects the radio wave, such as a satellite. Both effects can result in rotating radio waves, which can be minimized by a circularly polarized antenna.

Memory trick: “spin” in a ”circular” motion.

Last edited by tgoodrich860. Register to edit

Tags: arrl chapter 2 arrl module 2b

By calculations using the Keplerian elements for the specified satellite.

Keplerian elements are the inputs to a standard mathematical model of spacecraft orbits. Most often the calculations needed would include the Keplerian elements, an accurate time clock and your current location.

AMSAT Info on Keplerian elements

Last edited by kd7bbc. Register to edit

Tags: arrl chapter 2 arrl module 2b

A geosynchronous satellite is actually moving along its orbit just like any other satellite. It is at a height and position such that this orbital rotation matches the earth’s rotation and so it appears to be stationary.

LEO means "Low Earth Orbit" and HEO means "Highly Elliptical Orbit" and both are not relevant to this question. A geomagnetic orbit is not a thing, I think.

Hint: It’s the only question with stationary in it.

Last edited by kd7bbc. Register to edit

Tags: arrl chapter 2 arrl module 2b

http://www.aprs.org/

Automatic Packet Reporting System (APRS) is an amateur radio-based system for real time digital communications of information of immediate value in the local area. In addition, all data is ingested into the APRS Internet System (APRS-IS) and distributed globally for immediate access. Shared information contains global coordinates, altitude, speed, heading, text messages, alerts, announcements, and bulletins. The most visible aspect of APRS is its capability of map display. Anyone may place any object or information on the map, and it is distributed to all maps of all users in the local RF network, or to anyone monitoring the area via the Internet. Any station, radio, or object broadcasting GPS coordinates to the APRS system can be automatically tracked over time.

Last edited by w3mit. Register to edit

Tags: arrl chapter 2 arrl module 2b