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Grid dip oscillators were first developed in the 1920s and were built with vacuum tubes.The devices displayed the amplitude of the tube's grid current, hence GDO.. Modern dip meters are solid-state devices, and are sometimes called gate dip oscillators or emitter dip oscillators in reference to the analogous part of the transistor whose current is measured instead of a vacuum tube grid. [1]
[1] [2] [3] Similar devices can be made for detection of mobile phones. [4] As an alternative, a dip meter can be used. There are two categories of wavemeters: transmission wavemeters , which have an input and an output port and are inserted into the signal path, or absorption wavemeters , which are loosely coupled to the radio frequency source ...
MFJ Enterprises was an American manufacturer specializing in a wide range of products for the amateur radio market. The company focuses on station accessories, including antenna tuners and antenna switching equipment. MFJ was founded in 1972 by Martin F. Jue. As of 2014, the company was recognized as the largest producer of amateur radio ...
In addition, the FCC continues to require that all digital transmissions be centred on the channel-centre frequencies, which the Report and Order defines as being 1.5 kHz above the suppressed carrier frequency of a transceiver operated in the upper side-band (USB) mode. As amateur radio equipment displays the carrier frequency, it is important ...
The 15-meter band (also called the 21-MHz band or 15 meters) is an amateur radio frequency band spanning the shortwave spectrum from 21 to 21.45 MHz. The band is suitable for amateur long-distance communications , and such use is permitted in nearly all countries.
Repeater use sparked a huge interest in the 2-meter and 70-centimeter (420–450 MHz) bands; however, this interest never fully found its way into the 1.25-meter band. Many amateurs attribute this to the abundance of commercial radio equipment designed for 136–174 MHz and 450–512 MHz that amateurs could easily modify for use on the 2-meter ...
Martin F. Jue is an American business personality, inventor and founder/owner of several companies, including MFJ Enterprises, Hy-Gain, Cushcraft, [2] Ameritron, Vectronics and others, all of which manufacture products for the amateur radio industry. He holds numerous patents on specialized technology, especially in the area of T network field ...
[1] [2] Some of the output of the amplifying device is applied back to its input to add to the input signal, increasing the amplification. [3] One example is the Schmitt trigger (which is also known as a regenerative comparator ), but the most common use of the term is in RF amplifiers, and especially regenerative receivers , to greatly ...