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Microphones, headsets and accessories for amateur radio and professionals

The Elecraft K2 transceiver requires specific modifications for optimal soundcard digital mode operation, particularly for PSK31. The original article, circa 2001, details initial challenges with manual PTT and speech compression settings. A key modification involves adding headphone audio and a compression disable signal to the K2's microphone jack, utilizing pins 4 and 5. The **COMP0** signal, active low, is shorted to ground via a non-inverting open collector switch circuit, comprising two resistors and two transistors, mounted on the SSB board near U3. This circuit provides effective control of an analog signal line with good noise immunity. The switchbox itself repurposes a computer COM port switch, using only two of its original connectors and four of the nine poles. It integrates a microphone preamplifier, a PTT circuit built with 'flying leads' construction, and RCA jacks for soundcard connections. A trimpot adjusts the audio drive to the K2. The central DB9 connector links to the K2's mic connector via a shielded RS232 serial cable, ensuring proper grounding and signal routing. An external footswitch PTT jack is also included. Further enhancements include a **noise-canceling microphone** preamp based on a QST December 2000 article, adapted for Heil mic elements. This preamp, built with pseudo-Manhattan style construction, provides a gain of approximately 2 by changing emitter resistors (R9 and R16) from 680 ohms to 330 ohms. A 10-ohm series resistor and 47 µF capacitor on the +5V supply mitigate noise spikes.

On line shop in Greece for amateur radio products, electronics, DAB Radio and GPS. Dealer for popular amateur radio brands, heil sound, kenwood, MFJ and more

Audio setup at N2RIT built around the Yaesu FT-950 abd the Heil Sound PR-781 an ultraflex PRO EX3200

Review of the Heil PR-781 with a Yaesu FT-950 includes youtube movies and a nice product review

Amateur radio daler for Cushcraft Heil Sound, Hustler Kenwood Yaesu SGC amateur radio products in South Africa

Amateur Radio Store, dealer for DXZkit products, Heil Sound, Arrow, Miracle based in Northern Colorado