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Ntp Server Static GPS Antenna Systems

The Global positioning System (GPS) is often used by computer equipment, such as NTP Server systems, to provide an accurate timing reference for time critical applications. This article provides an overview of GPS for timing applications and describes the equipment used to install a GPS antenna in a static location.

Overview – Using GPS for Accurate Time

The Global Positioning System is a US military system for worldwide navigation. The system consists of 24 orbiting satellites, each satellite has a highly accurate atomic clock on-board synchronised to UTC time. The satellites continuously broadcast time and position information. The time and position information can be obtained worldwide with a GPS receiver and antenna. GPS works continuously in any whether conditions, anywhere in the world. Additionally, there is no set up fee or subscription charges to utilise the GPS systems. Many computer timing systems and NTP Server systems utilise GPS as an accurate external timing reference.

The Accuracy of GPS Timing Systems

GPS receivers provide highly accurate position and timing information. Typically, a GPS receiver can provide positioning information to an accuracy of 15m. NTP Server systems can obtain timing information from GPS to a resolution of a few nanoseconds.

The GPS Signal

The transmitted GPS signal is very weak low-power radio signal, designated L1 and L2. L1 is the civilian GPS frequency transmitted at 1575.42 MHz. The signals travel by line of sight and can pass through clouds, glass and plastics but are blocked by objects such as metal and brickwork. Therefore, the ideal location for a GPS antenna is on rooftop with a full 360-degree view of the sky. However, often installation on the side of a building or in a window can provide adequate results. As a rule of thumb, the better the view of the sky, the greater the likelihood of a good consistent signal lock.

GPS Timing Antenna Types

The GPS antenna acts as an amplifier to boost the GPS signal for transmission along a cable, usually coax, to the GPS receiver. GPS Timing antenna’s provided with NTP server systems utilise a pole-mounting system. The antenna screws to a threaded pole for installation on rooftops. This arrangement provides the GPS antenna with a rigid mount easily able to withstand high winds without damage. Typically the GPS antenna is fairly small in size, measuring less than 90cm in diameter. Low-cost patch type antennas are also available, but these are generally better suited to vehicle applications.

GPS Antenna Cable Types and Cabling Distances

The cable distance that can be utilised by a GPS antenna depends mainly on the amplification of the GPS antenna and the quality of coax used in the installation. A typical GPS timing antenna may have a gain of 35 db. Relatively low-quality coax such as RG58 has an attenuation of 0.64 db/m at 1575 MHz. Therefore, a cable run of 55m can be obtained using RG58 cable. With very high quality coax cable, such as LMR400, an unaided cable run of 200m can be achieved. However, very high quality coax can be expensive. A good price-performance compromise is LMR200 cable, which can be run unaided to 80m.

Extending Cabling Distance with In-Line GPS Amplifiers

In-line GPS amplifiers provide further amplification of the GPS signal to increase the cable distance between the GPS antenna and receiver. GPS amplifiers are fitted in-line with the antenna cable and obtain power from the receiver via the coax cable. No external power-supplies are required. Typically, a GPS amplifier may add a further 20 dB of gain, adding 30m of low-quality RG58 coax, 40m of LMR200 coax or 100m of high quality LMR400 coax. Additionally, multiple in-line amplifiers may be utilised to further increase cable distance.

Sharing a Single Antenna Between Multiple Receivers – GPS Splitters

GPS splitters allow a single GPS antenna to be utilised by two or more NTP server systems. The GPS splitter splits the signal received from the GPS antenna into multiple outputs for synchronizing multiple NTP servers. GPS splitters are generally available with 2, 4 or 8 outputs.

Protecting GPS Systems – GPS Surge Suppressors

Surge suppressors protect expensive NTP server equipment from electro-static discharges, such as lightning, that may be picked up by an externally mounted GPS antenna. Surge suppressors are installed in-line on the coax cable between the antenna and receiver, ideally where the cable enters the building. Surge suppressors require a low-impedance ground, to discharge any received surge. The surge suppressor requires no power-supply or additional cabling.

Ntp Server Static GPS Antenna Systems / David Evans

Dave Evans develops atomic clock time synchronisation systems to ensure accurate time on PC networks. Click here to find out more about GPS NTP Server systems.

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Vpn Loading Balancing

Virtual Private Networks form a major part of many organisations’ network infrastructure. They are often used as a vehicle to serve sensitive information to remote offices and workers. Typically VPN’s are created point-to-point making it difficult to add any resilience or more bandwidth. Introducing our products to this infrastructure makes this possible, whether you are implementing new or expanding existing VPN infrastructure.

Drawbacks of existing technology:
Single Point of Failure
Traditional VPN’s both client and site-to-site are based upon a single Internet link. Should this link fail, organisations invariably have no fall-back plan, and simply have to diagnose, report and wait.

Difficult to Scale
Should an organisation require more bandwidth to accomadate increasing demand, this is often proves difficult and is some cases impossible. This could mean expensive upgrades, change of ISP and most likely their complete Internet infrastructure.

Restricted Upload Speed of DSL connections
SME’s generally use DSL to serve their VPN connections. This can cause considerable bottlenecks and can prevent service being offered to clients should demand outgrow the supply.
Difficult to Prioritise Critical Data
Maintaining a single link increases the chance that bandwidth intensive services can saturate the entire amount of bandwidth and this can lead to loss of data and denial of important transmissions such as E-Mail and Web Services. Introducing a Load Balancing device into the network makes it possible segregate and route traffic based on priority. Furthermore all our Load Balancing products such Quality of Service (QoS) which can be used to limit these intensive applications in order to guarantee the avability to the critical ones.

Traffic Distribution and Failover:
Traffic distribution is done “by packet” and so a single data connection can assume all the available bandwidth. This could be a Voice Over IP call over Teleconferencing.

Should any active links fail, data is simply retransmitted down available links with no impact to the client.

Traffic distribution is done “by connection”, so protocol’s that use multiple connections (such as HTTP) have greater benefit with this method.

On link failure connections related to the failed link will be lost, however most applications will retry the connection, in which case the Load Balancer will route the new connection down an available link

Vpn Loading Balancing / Mark Henry

Mark Henry is the author related to Internet Link Aggregation & Resilience, Bandwidth Management, Link Bonding, Multihoming, Load Balancer, Dual Port Router, Multiple Gateways, Server Load BalancingXrio provide solutions for bandwidth management, load balancing, link bonding, server load balancing, multiple gateways, global traffic management, wan optimization, wan performance, isp, adsl, sdsl, dual port router, high availability router, local director, multihoming router, vpn clustering

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Cisco’s Catalyst 6500 Remains the Network Switch to Beat

San Francisco, California October 10, 2006: Following a lackluster Q3, Cisco Systems emerges as the leader in the 10 Gigabit Ethernet Switch Market for the fourth quarter. Fueled by increased demand and an overall rise in the average selling price, Cisco experienced significant gains in a market of over $300 Million.

With almost 70% of the projected $1.3 Billion 10-Gig market share and a more powerful, yet affordable design, the Catalyst 6500 is poised to cement Cisco as the dominating force in the industry. With the recent release of an eight-port, 10-Gigabit Ethernet module for the 6500, Cisco is quickly pulling away from the rest of the pack.

In addition, upgrades like the Application Control Engine (ACE) module have prompted companies like Pure Video Networks to adopt Cisco switches to manage traffic of their popular video websites. Implementing simultaneous data center services such as server load balancing, integrated network and application switching/security, the ACE module delivers the highest performance in the industry. The ACE Simplifies application infrastructure by combining the functionality of multiple application delivery appliances into a single module, including server load balancing and off-load, Secure Socket Layer (SSL) protocol, security, and application optimization capabilities.

Already the most successful networking switch on the IT market, the 6500 Series reduces existing operational costs and improves a network’s ability to respond to intensive bandwidth demands. In general, customers using the services modules for the Catalyst 6500 reduce their total cost of ownership by taking advantage of simplified infrastructure, improved investment protection, pervasive security, and the high levels of performance, scalability, and innovative technologies.

With over twenty unique service modules in five distinct categories, the Catalyst 6500 ranks among the most scalable, high-performance platform for integrated services. Currently, Cisco offers modules that address security issues, application, networking, network monitoring, wireless/mobility, and IP communications, which can be integrated into existing catalyst switches. Each modules offers upgraded performance and reinforces Cisco’s hold on the market for network switches. With more than $20 Billion is sales sine it’s release in 1999, the 6500 Series switch has become the most popular networking platform ever.

While Cisco has been able to fend off most threats to their position, rival Foundry Networks, and newcomer Force 10 have recently launched new 10Gbe ready products aimed at disrupting the company’s market share. According to literature on Force 10’s Terascale E-Series 1200, the E1200 boasts of more than double the ports of the Catalyst 6500 (1260 vs. 576 Ethernet ports/chassis). While this may be good news for the company, Force 10 has been focused on the data center vertical, and is therefore still untested in the enterprise market. Foundry’s BigIron RX series switch has received favorable press for it’s size/performance ratio and lower prices. With the launch of the new RX series, Foundry has mounted a consistent affront to Cisco’s unchallenged reign.

Even with the competition mounting new efforts, the Cisco name is still a major factor among IT professionals whose networks depend on their equipment. Fortunately for the stalwart Cisco, reputation is still the key to market dominance.

Cisco’s Catalyst 6500 Remains the Network Switch to Beat / Pankaj Mohan

Oliver Rowen is currently Director of Corporate Accounts for Townsend Assets Group (TAG), a leading reseller of pre-owned data networking and refurbished equipment like the Catalyst 6500. With more than 2500 customers in 23 countries, TAG helps customers acquire, manage and remarket their technology. For more information go to www.townsendassets.com

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