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TS2000 audio setup - June 2008

This article describes the audio configuration of the TS2000 at VK1OD in June 2008.

The problem

The dynamic hand mic supplied with the TS2000 is quite susceptible to magnetic flux, and leakage from the nearby AL-811H amplifier results in low level hum in the transmit audio depending on the proximity and orientation of the microphone.

A solution

A number of options were explored for solving this problem, and the one currently pursued is a Alinco EMS-57 electret hand microphone. The EMS-57 is pin compatible with the Kenwood microphone, it has UP and DOWN buttons and a DTMF keypad.

Fig 1:

Fig 1 shows the Alinco EMS-57. The EMS-57 has slightly higher output than the original Kenwood microphone, so the transceiver needs adjustment (see below).

Performance

Observers offering flattering audio reports often attribute the signal quality to the non-standard audio setup. In fact, the non-standard audio setup doesn't sound very different to the original microphone.

The transmitter is normally used with the Speech Processor active.

Fig 2:

A test was conducted by speaking a test message into both microphones and recording the tx audio from the TX MONI output. Fig 2 shows the spectral distribution of the test message firstly on the EMS-57 microphone and then on the original Kenwood hand mic. There is very little difference in the spectral content. 

Audio quality is mainly attributable to appropriate adjustment of audio levels and drive level to the PA to minimise the risk of overdrive.

The process is:

The AL811H ALC is connected to the TS2000, but is adjusted so that it will not develop control voltage until well above 400W PEP, it is a measure for reducing grid damage from accidental gross overdrive rather than normal power control. (The ALC response is way to slow to use it effectively for normal power control.)

Links

 

Changes

Version Date Description
1.01 03/06/2008 Initial.
1.02    
1.03    

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