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  • gerardoberger 2:38 am on October 24, 1985 Permalink | Reply
    Tags: 21   

    Real-world Two way radios 

    Can not get over how inexpensive the communication security device is now, an amazing deal for a top-end product!

    With all this talk about frequencies and wattage, you might be wondering about the real-world range of walkie-talkies. Commercial-grade radio have enough oomph to give them a range of several miles in ideal conditions. But as with so many product specifications, manufacturers often wildly exaggerate the range of their walkie-talkies, sometimes claiming that they’ll work at more than 20 miles (32 kilometers).

    But in areas where there are buildings, hills, trees or any sort of obstructions at all, expect the working range to drop in a hurry. In very congested areas, even good-quality radios may max out their range in several hundred feet.

    Once you’re within range of another handset, there’s still the matter of conducting a proper walkie-talkie conversation. Because only one person can speak at a time, each walkie-talkie operator needs to know the rules. For example, saying “over” indicates that you are done speaking and that you’re awaiting a reply. Alternately, by saying “over and out,” you’re telling listeners that you’re done with your transmission and that the conversation is over. These so-called voice procedures are necessary to prevent people from talking over each other during transmission.

    As walkie-talkie features become more advanced, some of these linguistic acrobatics are becoming less necessary. For instance, some radios send a beep tone when you release the PTT button, in effect replacing “over” with an automatic tone.

    Radio lexicon can be a strange language for radio novices. But what’s even weirder? The sound of a stranger’s voice on your handset.

    If another person’s radio is within range of yours and it happens to be set to the same channel, there’s a chance that you’ll hear what he or she is saying, and vice versa. To prevent this, your group can select a different channel, or you can invest in walkie-talkies with CTCSS (continuous tone-coded squelch system) or DCS (digital-coded squelch) encoding.

    This encoding isn’t encryption at all — that kind of functionality is found only in military-grade radios. Instead, the encoding is just a type of filtering. In other words, your radio’s speaker will only activate when it receives a transmission from another radio that precedes its message with a specific tone combination. Your group’s radios, of course, must all be using the same privacy code in order to work with each other.

    Even with privacy codes in place, Walkie Talkie conversations are anything but secure. Think of these transmissions as publicly-accessible phone calls. Spewing weird rants or private details over the air violates basic radio etiquette and might garner some really unwanted attention from aggravated users.

     
  • gerardoberger 6:51 am on May 17, 1982 Permalink | Reply
    Tags: 21   

    How To Use Distant Measuring Equipment Within A Flight Planner 

    What’s your favourite feature of the device communication error 5012 hplip? Personally, I like the design job – It is cooler than an Inuit’s underpants!

    What is distance measuring equipment that is used within a flight planner?

    Distance measuring equipment is a transponder based 2 way radio navigation technology that measures slant range distance by timing the propagation delay or VHF or UHF radio signals. Developed in Australia, it was invented by Edward George Bowen while employed as Chief of the Division of Radio physics of the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

    Another engineered version of the system was deployed in the early 1950s operating in the 200 MHz VHF band. The Australian domestic version was referred to by the Federal Department of Civil Aviation as DME (D) and the later international version adopted by ICAO as DME.
    DME is similar to secondary radar, except in reverse. This system was a post war development of the IFF systems of World War II. To maintain compatibility, DME is functionally identical to the distance measuring component of TACAN used within a flight planner.

    Operation
    Aircraft use DME to determine their distance from a land based transponder by sending and receiving pulse pairs. These are two pulses of fixed duration and separation. The ground stations are typically located with VORs. A typical DME ground transponder system for en-route or terminal navigation will have a 1 kW peak pulse output on the assigned UHF channel.

    A low power DME can also be co-located with an ILS glide slope antenna installation where it provides an accurate distance to touchdown function, similar to that otherwise provided by ILS Marker Beacons.
    Distance calculation and accuracy used within a flight planner
    When using a flight planner, a radio pulse takes around 12.36 microseconds to travel 1 nautical mile to and from and it is also referred to as a radar mile. The time difference between interrogation and reply 1 nautical mile minus the 50 microsecond ground transponder delay is measured by the interrogator’s timing circuitry and translated into a distance measurement (slant range) which is stated in nautical miles and then displayed on the cockpit DME display.

    The accuracy of DME ground stations is 185m. Its important to know that DME provides the physical distance from the aircraft to the DME transponder. This distance is often referred to as ‘slant range’ and depends trigonometrically upon both the altitude above the transponder and ground distance from it in a flight planner.

     
  • gerardoberger 4:01 am on November 26, 1970 Permalink | Reply
    Tags: 21   

    Walkie Talkie vendors hope Lake County officials can hear them 

    When we found this post we were so excited, having looked for over one year for this, finding it on this site was an thrilling day for me.

    The latest in public safety communications radios were on display Tuesday to municipal and Lake County officials preparing to buy millions of dollars in new hardware.

    Miner Electronics, of Munster; Tri-Electronics, of Hammond; EF Johnson, of Irving, Texas; Harris Corp., of Lynchburg, Va.; and Motorola Solutions, of Schaumburg, Ill., were among the communications companies taking part in a demonstration at the Slovak Club. On display were the next generation of portable and mobile two Way Radios first responders soon will be sporting.

    The state has mandated the county consolidate the 17 city, town and county police, fire and emergency medical dispatch centers into a single countywide network by the end of this year.

    They must be compatible with Motorola’s interoperable 700 megahertz P25 Trunked Voice radio infrastructure the county recently purchased, making almost all current radios obsolete.

    Jack Allendorf, the county’s deputy E-911 director, said Tuesday the demonstration is to help city and town officials decide which radios their police officers, firefighters and EMS workers will need in the field.

    The new radios are supposed to provide clear voice signals by canceling out surrounding noise at crime, fire and accident scenes. Their signals are supposed to penetrate masonry and metal buildings better than current models.

    Motorola presenters said the portable radio is designed to provide the same clear audio for police officers chasing a suspect on open streets as for firefighters deep inside a burning building.

    The county could need as many as 4,000 new communications units.

     
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