April Fools Shows
Dave has not left and HPR has not sold out
Last Month's Shows
Comments this month
These are comments which have been made during the past month, either to shows released during the month or to past shows.
There are 24 comments in total.
There are 3 comments on 3 previous shows:
- hpr2708 (2018-12-19) "Ghostscript" by klaatu.
- Comment 2: Klaatu on 2019-03-07: "You're welcome"
- hpr2749 (2019-02-14) "Lostnbronx and Klaatu commentary from episode 2743" by klaatu.
- Comment 1: Klaatu on 2019-03-07: "We are stupid"
- hpr2759 (2019-02-28) "Cleaning the Potentiometers on a Peavey Bandit 65" by Jon Kulp.
- Comment 2: Jon Kulp on 2019-03-02: "Never too much about 80s gear"
There are 21 comments on 12 of this month's shows:
- hpr2761 (2019-03-04) "HPR Community News for February 2019" by HPR Volunteers.
- Comment 1: Mike Ray on 2019-03-04: "Media embedded show notes"
- hpr2762 (2019-03-05) "What You Really Are" by lostnbronx.
- Comment 1: tuturto on 2019-03-05: "oh, wow"
- hpr2763 (2019-03-06) "Deepgeek explains SPF records" by klaatu.
- Comment 1: b-yeezi on 2019-03-09: "Thanks for the help"
- Comment 2: pauleb on 2019-03-11: "Great explanation!"
- hpr2764 (2019-03-07) "Personal password algorithms" by klaatu.
- Comment 1: Steve on 2019-03-12: "LessPass"
- hpr2766 (2019-03-11) "Disk enumeration on Linux" by klaatu.
- Comment 1: Joel D on 2019-03-12: "The Letters C and F"
- Comment 2: Klaatu on 2019-03-13: "Thanks for the info Joel"
- Comment 3: Ahuka on 2019-03-14: "Old drive letters"
- hpr2768 (2019-03-13) "Writing Web Game in Haskell - Planetary statuses" by tuturto.
- Comment 1: Klaatu on 2019-03-15: "Agog and aghast"
- Comment 2: tuturto on 2019-03-15: "this made my week"
- hpr2773 (2019-03-20) "Lead/Acid Battery Maintenance and Calcium Charge Voltage" by Floyd C Poynter.
- hpr2774 (2019-03-21) "CJDNS and Yggdrasil" by aldenp.
- Comment 1: tuturto on 2019-03-21: "fascinating"
- Comment 2: Brian-in-Ohio on 2019-03-21: "more shows"
- Comment 3: norrist on 2019-03-21: "gentoo"
- Comment 4: Gavtres on 2019-03-25: "IPv6 end to end encryption"
- hpr2776 (2019-03-25) "Sub-Plots In Storytelling" by lostnbronx.
- Comment 1: operat0r on 2019-03-25: "fun stuff"
- hpr2777 (2019-03-26) "The quest for the perfect laptop." by knightwise.
- Comment 1: Beeza on 2019-03-29: "Computer Requirements Specification"
- hpr2778 (2019-03-27) "Functor and applicative in Haskell" by tuturto.
- Comment 1: Beeza on 2019-03-28: "Intuitiveness Of Haskell"
- Comment 2: tuturto on 2019-03-29: "thanks and great idea"
- hpr2779 (2019-03-28) "HTTP, IPFS, and torrents" by aldenp.
- Comment 1: Hipstre on 2019-03-31: "Enjoyed it, sounded great"
Mailing List discussions
Policy decisions surrounding HPR are taken by the community as a whole. This discussion takes place on the Mail List which is open to all HPR listeners and contributors. The discussions are open and available on the HPR server under Mailman.
The threaded discussions this month can be found here:http://hackerpublicradio.org/pipermail/hpr_hackerpublicradio.org/2019-March/thread.html
Any other business
Did we mention the The Mint Cast ?
There was a misunderstanding about Yannick’s show 2740 when it was discussed on the February Community News. The show was about
Pop_OS!, a subject Yannick had also spoken about previously on an edition of the TuxJam podcast.
The misunderstanding was that we thought this might have gone against guidelines on syndication, where in fact it did not. It was merely a case of the same subject being spoken about by the same person on two different podcasts.
Change to the host page
The page for each host:
which used to contain a list of all shows contributed by that host, with the show notes, has been made more compact. It now displays only the title, release date, duration, series (if applicable), tags and the show summary. Clicking on the title takes you to the show itself.
The list of all hosts in alphabetic order can be seen at http://hackerpublicradio.org/correspondents.php (navigate with the top menu bar: Home→About→Hosts). From there clicking on the host number takes you to the page for that host. There’s also a link to the host page from the page for each show.
Community News Calendar
An iCal calendar has been prepared which holds the next 12 recording dates for the Community News. This calendar can be downloaded and opened by suitable clients such as the Thunderbird mail client or Google Calendar. The file is linked from http://hackerpublicradio.org/about.php and may be downloaded from http://www.hackerpublicradio.org/HPR_Community_News_schedule.ics.
Tags and Summaries
Over the period tags and/or summaries have been added to 32 shows which were without them.
If you would like to contribute to the tag/summary project visit the summary page at http://hackerpublicradio.org/report_missing_tags.php and follow the instructions there.
Ken did not fall of the roof in a storm
This show is dedicated to Procrastination, the avoidance of doing a task which needs to be accomplished.
I've been trying to record this particular show for ages but I can never seem to finish it. I find the topic just too interesting. When I start then I get distracted by some other aspect. Every time I try to record it Murphy gets in the way, with lost recordings and broken cards etc. This is the email that prompted this show.
-------- Forwarded Message -------- Subject: TWAT - Satellite communications Date: Tue, 13 Dec 2005 12:00:54 +0100 Hi Droops, I heard your call for content and I'd like to send you some shows. I don't have a lot of spare time with work and a young family so I can't do a regular show but I can send you a series on a topic. I was thinking of doing a series on Satellite Communications. ... Ken
So after eleven years, I set the deadline of episode 2000 to force myself to finish this show.
What are orbits ?
In physics, an orbit is the gravitationally curved path of an object about a point in space, for example the orbit of a planet about a star or a natural satellite around a planet. Orbits of planets are typically elliptical, and the central mass being orbited is at a focal point of the ellipse.
Newton's cannonball was a thought experiment Isaac Newton used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion. It appeared in his book A Treatise of the System of the World.
- No orbit
- Suborbital trajectories, trajectory intersects the atmosphere so that it does not complete one orbital revolution.
- Orbital trajectories (or simply "orbits")
- Open (or escape) trajectories
It is worth noting that orbital rockets are launched vertically at first to lift the rocket above the atmosphere (which causes frictional drag), and then slowly pitch over and finish firing the rocket engine parallel to the atmosphere to achieve orbit speed.
Once in orbit, their speed keeps them in orbit above the atmosphere. If e.g., an elliptical orbit dips into dense air, the object will lose speed and re-enter (i.e. fall). Occasionally a space craft will intentionally intercept the atmosphere, in an act commonly referred to as an aerobraking maneuver.
Types of orbits
There are many ways to classify orbits
The choice of which orbit to use is based on the intended purpose of the satellite.
- Centric classifications: Based on what they orbit
- Altitude classifications: Based on how high they are
- Inclination classifications: Based on the angle of rotation with respect to the Equator.
- Eccentricity classifications: Based on their path
- Synchronicity classifications: Based on how often they rotate
Low Earth orbit (LEO)
0 to 2,000 km (0–1,240 miles).
- 0 km / mi - Sea Level.
- 37.6 km / 23.4 mi - Self Propelled Jet Aircraft Flight Ceiling (Record Set in 1977).
- 215 km / 133.6 mi - Sputnik-1 The first artificial satellite of earth.
- 340 km / 211.3 mi - International Space Station.
- 390 km / 242.3 mi - Former Russian Space Station MIR.
- 595 km / 369.7 mi - Hubble Space Telescope.
- 600 - 800 km / 372.8 - 497.1 mi - Sun-synchronous Satellites.
These satellites orbit the Earth in near exact polar orbits north to south. They cross the equator multiple times per day and each time they are at the same anglewith respect to the sun. Satellites on these types of orbits are particularly useful for capturing images of the Earth’s surface or images of the sun
Medium Earth orbit (MEO)
Geocentric orbits ranging in altitude from 2,000 km (1,240 miles) to just below geosynchronous orbit at 35,786 kilometers (22,236 mi).
GPS (Global Positioning System) Satellites reside here. These Satellites are on a Semi-synchronous Orbit (SSO) meaning that they orbit the earth in exactly 12 hours (twice per day)
Geosynchronous orbit (GSO) and Geostationary orbit (GEO)
Orbits around Earth matching Earth's sidereal rotation period. 42,164 km (26,199 mi). Sidereal time is a "time scale that is based on the Earth's rate of rotation measured relative to the fixed stars" rather than the Sun. https://en.wikipedia.org/wiki/Sidereal_time
Geosynchronous satellites orbit the Earth at the same rate that the Earth rotates. Thus they remain stationary over a single line of longitude. A geostationary satellite will remain in a fixed location as observed from the surface of the earth, allowing a satellite dish to be alligned to it.
High Earth orbit
Geocentric orbits above the altitude of geosynchronous orbit 35,786 km (22,240 miles).
They are often used for earth-mapping, earth observation, capturing the earth as time passes from one point, reconnaissance satellites, as well as for some weather satellites. The Iridium satellite constellation also uses a polar orbit to provide telecommunications services. The disadvantage to this orbit is that no one spot on the Earth's surface can be sensed continuously from a satellite in a polar orbit.
Orbita was a system that consisted of 3 highly elliptical Molniya satellites, Moscow-based ground uplink facilities and about 20 downlink stations, located in cities and towns of remote regions of Siberia and Far East. Each station had a 12-meter receiving parabolic antenna and transmitters for re-broadcasting TV signal to local householders.
Atmospheric electromagnetic opacity
Sputnik 1 was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on October 4, 1957. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennae to broadcast radio pulses. It was visible all around the Earth and its radio pulses were detectable. This surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the larger Cold War. The launch ushered in new political, military, technological, and scientific developments.
ProtoStar II Mission Overview
ASTRA 2G SATELLITE MISSION
ASTRA 2G is the third spacecraft of a three satellite investment programme (ASTRA 2E, 2F and 2G) that SES contracted with Airbus Defence and Space in order to provide replacement as well as incremental satellite capacity in the orbital arc of 28.2/28.5 degrees East.
ASTRA 2G carries 62 Ku-band transponders as well as 4 Ka-band transponders. The different beams provide coverage over the UK and Ireland, Europe and West Africa.
Components of a Communications Satelites
- Rocket motors
- Fuel tanks
- Solar panels
- Antennas and transceivers/transponders
The word "transponder" is derived from the words "transmitter" and "responder."
A communications satellite's transponder is the series of interconnected units that form a communications channel between the receiving and the transmitting antennas. It is mainly used in satellite communication to transfer the received signals.
A transponder is typically composed of
- An input band limiting device (a band pass filter)
- An input low-noise amplifier (LNA), designed to amplify the (normally very weak, because of the large distances involved) signals received from the earth station
- A frequency translator (normally composed of an oscillator and a frequency mixer) used to convert the frequency of the received signal to the frequency required for the transmitted signal
- An output band pass filter
- A power amplifier (this can be a traveling-wave tube or a solid state amplifier)
Boeing commercial communications satellites geosynchronous orbit
Finding Astra 28.2E
This is one of the many sites that will give you a birds eye view of where you need to point your dish.
Terms needed when pointing a dish
The Dish, on Kens Roof.
Reading the elevation from the dish assembley.
Freesat is broadcast from the same satellites (Astra 28.2E and Eurobird 1) as Sky Digital.
This is a list of all of the free-to-air channels that are currently available via satellite from SES Astra satellites (Astra 2E/2F/2G) located at 28.2 °E.
Here is a link to a page on how to get mythtv working with FreeSat.
Your passwords are as secure as they ever were
On September the 10th, 2012 an anonymous malicious hacker released 10,000 pin codes onto the site paste bin dot com. How the attacker gained access to the codes is not known, but it is thought that it may be linked to a breach that occurred at the end of March 2012 to the Credit card processor Global Payments. That attack exposed 1.5 million consumers financial data. These codes have been confirmed by security experts to be legitimate and in wide spread use even today. Despite this exposure been "common knowledge" among the security community, major banks and credit card companies have yet to issue any statement on the breach.
Tired of waiting for action by big business, we bring you a list of the codes so you can check for yourself if your data is compromised.
Yes we would listen to them reading a phone book. A link for the younger listeners that may have never seen a https://en.wikipedia.org/wiki/Telephone_directory.
In today's show we continue our look at The OSI model for network communications, with examples of Layer 3 been given with particular focus on Geography diverse Host addressing.
From Wikipedia: https://en.wikipedia.org/wiki/OSI_layer_3
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.
The network layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host via one or more networks, while maintaining the quality of service functions.
Functions of the network layer include:
- Connection model: connectionless communication
- For example, IP is connectionless, in that a datagram can travel from a sender to a recipient without the recipient having to send an acknowledgement. Connection-oriented protocols exist at other, higher layers of the OSI model.
- Host addressing
- Every host in the network must have a unique address that determines where it is. This address is normally assigned from a hierarchical system. For example, you can be "Fred Murphy" to people in your house, "Fred Murphy, 1 Main Street" to Dubliners, or "Fred Murphy, 1 Main Street, Dublin" to people in Ireland, or "Fred Murphy, 1 Main Street, Dublin, Ireland" to people anywhere in the world. On the Internet, addresses are known as Internet Protocol (IP) addresses.
- Message forwarding
- Since many networks are partitioned into subnetworks and connect to other networks for wide-area communications, networks use specialized hosts, called gateways or routers, to forward packets between networks. This is also of interest to mobile applications, where a user may move from one location to another, and it must be arranged that his messages follow him. Version 4 of the Internet Protocol (IPv4) was not designed with this feature in mind, although mobility extensions exist. IPv6 has a better designed solution.
Within the service layering semantics of the OSI network architecture, the network layer responds to service requests from the transport layer and issues service requests to the data link layer.
How better to explain it than by sending it out in Morse Code http://hackerpublicradio.org/eps.php?id=1343.
In this the first in a series exploring The Open Systems Interconnection (OSI) model (ISO/IEC 7498-1)
From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/OSI_model
The Open Systems Interconnection (OSI) model (ISO/IEC 7498-1) is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar communication functions are grouped into logical layers. A layer serves the layer above it and is served by the layer below it.
For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while it calls the next lower layer to send and receive packets that make up the contents of that path. Two instances at one layer are connected by a horizontal connection on that layer.
In today's show Ken starts off with a practical example of Layer One, the The Physical Layer, https://en.wikipedia.org/wiki/Physical_layer. Although we are limited to audio for the purposes of the show, the same techniques could and are used across the light spectrum.