April 24, 2017BridgeCom Systems, IncPhone: (816)532-8451 E-Mail: tim@BridgeComSystems.comContact: Tim KingPress Release: NEW BCM-144 & BCM-440 Mobile Radios Now Shipping________________________________________________________________________BridgeCom Systems, Inc is pleased to announce the availability of BCM-144 and BCM-440 Mobile Radio for the amateur radio market. The join...
Reviewed by Pascal Villeneuve, VA2PV
In the past few years, VHF/UHF digital voice communication has been one of the fastest growing segments of Amateur Radio. D-STAR and System Fusion (C4FM) were specifically designed for Amateur Radio, but this is not the case with DMR — Digital Mobile Radio. It is an open standard, developed by the European Telecommunications Standards Institute (ETSI). As such, this technology is available to any company willing to build a digital radio, such as the BridgeCom Systems D-500 (by TEKK) reviewed this month. Introduction to DMR There are three types of DMR — Tier I, Tier II, and Tier III. To learn more about DMR, I strongly suggest that you read “Introduction to Digital Mobile Radio (DMR)” by John S. Burningham, W2XAB, in the October 2015 issue of QST. In this review, we will concentrate on the widespread Tier II DMR network. You will need to understand a bit about this technology to program your DMR radio. As DMR was not developed specifically for Amateur Radio, the terms are different from what we are used to. Tier II DMR uses TDMA (Time Division Multiple Access), which is a frequency-sharing protocol. You can have two conversations on the same frequency without interfering with each other. This is very efficient, as Tier II TDMA uses a 12.5 kHz bandwidth with two time slots. The switching is very fast, thus allowing for two simultaneous contacts on the same frequency, using this time-sharing method.
International Crystal Manufacturing (ICM) of Oklahoma City has announced that it will be going out of business, probably at the end of May. Royden Freeland Jr., W5EMH, son of the company’s founder, posted a letter this week on the ICM website.
“We will be honoring all orders that we have already taken and will be able to fill a limited amount of new orders dependent upon raw materials available,” Freeland said. “We would like to thank you for your past business. The success of ICM over the previous 66 years has been largely due to its amazing customer base.”
International Crystal produces RF control devices — quartz crystals, oscillators, QCM crystals, filters, TCXOs/VCTCXOs, and precision crystals.
November 14, 2015BridgeCom Systems, IncPhone: (816)532-8451 E-Mail: tim@BridgeComSystems.comContact: Tim KingFor Immediate ReleaseIntroducing the NEW BCD Duplexers by BridgeCom Systems________________________________________________________________________BridgeCom Systems, Inc is pleased to announce the availability of the BCD line of duplexers for the amateur and commercial radio markets....
Receiver desense testing by Karl Shoemaker, AK2O
Due to the inability of certain people to communicate properly and understand all the aspects of site testing this page was created to read, compare notes and build on for the benefit of all. Human communication, comprehension and understanding problems is beyond the scope of this document, however the reader should keep these problems in mind when dealing with site issues and interfacing with other companies and government Agencies. Misunderstandings, bogus readings, log entries, technician and management diagnostics and plan of actions for problem solving are commonly mis-directed with considerable time and expense wasted in the wrong direction of efforts. This can lead to the general desensitation (pun intended) and poor attitude of the workforce in most any private company or government in the technical (repair) field around this country. Fortunately, there still is a handful of technicians that care to understand what the problem is and the proper way to solve, or at least, reduce the symptoms to an acceptable figure. If you are reading this it's most like you are in one of the latter. This is a good thing.