This is what it is all about, fun in Ham Radio.  Those of you who have allowed yourselves to become appliance operators are missing the real substances of the hobby.  Know what makes it tick!

 

            The goal of this day’s activity was to plot the dynamic audio frequency characteristics of the echolink transceiver and determine what if anything could be done to improve its performance.

 

            The first thing needed was an audio generator.  Out of storage came an Eico model 377, probably forty years old, and had not been turned on in the last twenty years.  It was plugged into an AC wall socket, standing at some distance in anticipation of the electrolytic exploding; the power switch was turned on.  Pilot light lit, no smoke, a speaker hung on its output sounded great, and a frequency counter verified that its calibration was still accurate.  Next a Kenwood G71A handheld was cabled to the generator and we were ready to become an AT&T Sound Lab.

 

            We found the device under examination (Kenwood 711) was showing a high frequency enhancement and a low frequency roll off.  Frequency amplitudes between 1000 and 3000 Hz were being increased in the order of 6DB while those below 1000 Hz were down 6DB.  The 6DB change point was determined to be at 700 Hz on the low side and 2000 Hz on the high end. This simply means that everyone using the system sounded high pitched, tight shorts with sharks in the water.

 

            The bottom line when all of this was discovered was to install an equalizing circuit.  This consisted of a 10,000 ohm resistor in series, and a .01 cap to ground between the output of the transceiver and the audio input of the computer.  This reduced the high end problem and reversed the low end roll off.  This is a simple circuit, much like you would find in the tone control of a broadcast radio.

 

            The pictures that follow show how much fun you can have, when your better half does not know where you are. 

(GRIN)