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          New D-104 Audio Processing ... the K7DYY MK2             
and the SuperSenior   Class D AM Amateur Transmitter

Introducing the K7DYY D-104 Audio Processor MK2

I am introducing a new version of the D-104 audio processor with features used in broadcast type audio processing chains in addition to the compression and limiting of the original version.

The phase rotator circuit has been used for many years in the broadcast industry to provide louder audio without introducing distortion. Here is a link to an article by Gary Blau W3AM, a broadcast consultant engineer describing the technique:


The new D-104 MK2 processor incorporates the phase rotator while retaining the same size as the original D-104 processor. The new MK2, like the original audio processor, still fits in the base of the venerable D-104 microphone stand!


The compression averaging time has been extended to avoid having the noise gate open between words. The noise gate threshold has also been lowered. In addition, a jumper has been added to allow the noise gate function to be disabled completely for operation in a quiet room.


A low pass filter has been added to provide a gently rolloff above 6khz to reduce broadband noise from the D-104 microphone.

K7DYY SuperSenior

Index Laboratories  has introduced a new class "D" AM amateur transmitter and continues to improve it! Following in the footsteps of the Junior and the Senior, the new SuperSenior lives up to it's name. It's SUPER!

Let's first look at class "D" design. In the past, transmitters in this power category required huge amounts of primary power and produced heat due to inefficiency.  Not so with the SuperSenior. It plugs right into a standard 115 VAC power source and sips it. At full power, with no modulation, the SuperSenior draws under 5 amps.

Audio quality is a hallmark of this class of transmitter and the SuperSenior won't dissappoint you either! The audio is crisp and clear, whether you are using the K7DYY audio processor that mounts in the base of your D-104 or some other external audio processing gear.

The SuperSenior operates on the two most popular AM amateur bands, 160 meters and 80 meters, with full band coverage. You will notice that there is no tuning required when changing frequencies or bands! Simply select your desired operating frequency with the panel switch and LCD readout and you are ready to go.

The new SuperSenior operates at the full legal AM amateur power limit of 375 watts of carrier and will reach 1500 watts peak when fully modulated and it will do this all day and night long! It may surprise you but this all fits in the package shown in the picture, 3.5 inches high, 19 inches wide, and 5 inches deep and weighs almost 10 pounds! 

With the Junior you had to supply crystals for your operating frequency. The Senior included 6 of your selected frequencies. The SuperSenior now has a PLL (VFO) that can be set in 1 khz steps across the both bands.

The SuperSenior has most of what any AM amateur operator could wish for and all in one small package. It even has built in transmit/receive switching to provide convenient and reliable changeovers. Also, the SuperSenior has been designed to protect itself in all but the most abusive situations. All of the transmitter modules are built in die cast boxes and the front panel nomenclature is engraved. It's just pure quality!

Before you decide to order yours, please check with me regarding availability. You can click on the email link below.

73 Bruce K7DYY                                                     

Ordering Information

See the "PRODUCTS" page for prices and ordering. Payment may be made via Credit Card, through Paypal, or by check or money order. Prices shown are for assembled and tested units and do not include shipping, except as indicated.

  Email to Bruce  K7DYY


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