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By WA8AHZBen Mills, N4CV returns to QCWA Ch 91 to update the Chapter of Digital Mobile Radio.
DMR Presentation for QCWA 6-2020.pdf
By HC/STAFFUniquely designed Electromagnetic Radiation Spectrum chart going from Ultra Low Frequency to Gamma Rays.
Link to the author's website: http://unihedron.com/projects/spectrum/moreinfo.php
Additional content here: http://unihedron.com/index.php
By K3MRIRECOMMENDATION 832
WORLD ATLAS OF GROUND CONDUCTIVITIES
The CCIR, considering
a) that for ground-wave field strength prediction, it is essential to know the electrical characteristics of the ground along the path. In cases involving coordination between administrations, it is therefore often necessary to know the ground characteristics existing outside national boundaries;
b) that the most important electrical characteristic of the earth for frequencies below 3 MHz is the conductivity;
c) that there is a need for suitable conductivity charts when planning all types of radiocommunication, including
navigational services, in the VLF, LF and MF bands;
d) that conductivity maps are not yet available from all administrations,
1. that the information contained in Annex 1, which is a World Atlas of Ground Conductivities, be used to obtain the best estimate of conductivity for planning purposes;
2. that in presenting new or revised conductivity maps for updating the Atlas, standard values be used as indicated in Table 1.
By K3MRIThe development of digital modes has opened the doors of EME (Earth-Moon-Earth) communications to small stations, compared with the standards of equipment previously required for CW moonbounce. Even more, it revealed the CW EME capabilities of these small stations, many of them having no antenna elevation system (as in my case). All this can be achieved or, at least helped, thanks to the so-called “Ground Gain”.
Ground Gain has been emphasized by the 144 MHz EME community, but it is also of prime interest for the terrestrial propagation modes. Indeed, we will see below that if the free space antenna gain of a station is an important parameter, the environment surrounding the antenna is as much important, if not even more.
Apart the well known article of Palle, OZ1RH [1a] about the Ground Gain (focusing on tropo-scatter), there has not been a lot of articles on that topic in the amateur literature.
This article, focusing on 144 MHz band, is the result of researches in the literature and own experiments. It has been published in the German magazine “DUBUS” (in English and German languages), issue 3/2011.
By K3MRIOur new K4 doesn’t just harness the latest technology: it blends new tech with a classic user interface to create a transceiver that’s more than the sum of its parts. One that’s sophisticated, yet civilized.
Like you, we’ve witnessed the recent revolution in direct sampling and SDRs. But rather than rush toward change, we’ve been observing — saving the best ideas, testing them, and quietly merging them into a new kind of radio. The resulting modular, hybrid design is innovative and versatile, yet still a pleasure to use.
In particular, operators who’ve used our K3S transceiver and P3 panadapter will find the K4’s controls familiar, and its complement of I/O compatible with their existing station. But they’ll also discover a new level of convenience in the bright, 7” touch display, which combines a large panadapter with three intuitive multi-function controls. Everything you need is at your fingertips, including a unique built-in help system.
Three K4 Flavors
There are three K4 models to choose from: the basic K4; the K4D, which adds diversity receive capability; and the K4HD, which goes a step beyond other direct-sampling SDRs, adding a dual superhet module for the ultimate in blocking and close-in dynamic range.
A basic K4 can be easily upgraded to a K4D at any time by adding the KDIV4 option.
Similarly, a K4D can be upgraded to a K4HD by adding the KHDR4.
The K4 and K4D, like other “pure” direct-sampling radios, do not require crystal roofing filters. Digital signal processing is used to provide advanced demodulation, filtering, and signal display. The K4HD can operate either in direct-sampling or superhet mode. Typically the latter is only needed in the presence of extreme signals.
Modularity that Adapts to Your Needs
Flexibility — now and in the future — was a major design goal for the K4. All of Elecraft’s transceivers embody this philosophy. You can tailor the radio to your current needs, with one of the three models described above as well as other options. But you’ll also be ready to take advantage of new technology that in some cases hasn’t even been invented. Modules are segmented strategically to allow updates at a moderate cost so you won’t have to invest in a new radio every couple of years. Elecraft also listens to its community: the best ideas often translate into new options and software features.
Advanced Remote Control, Host Interfacing, and Display
With the K4, you can operate at the radio itself or from anywhere — whether it’s your living room, back porch, or halfway around the world. One K4 can control another, including streaming panadapter display. you can also use a tablet, netbook, or desktop PC. When operating the radio directly, you can use both the built-in LCD and an external monitor (HDMI), with different content.
Application programmers will benefit from the K4’s rich, yet easy to use command set, including many new commands for setting up panadapter and audio streams.