N6EX Repeater Exciter

TK-931 Photo
The exciter used for the N6EX 900 MHz repeater is a modified version of a Kenwood TK-931 trunked mobile transceiver. This radio was first produced in 1990, but is still in Kenwood's product line (as of 2006). The specified transmit range for the radio is 896 - 902 MHz and 935 - 941 MHz; however, no modifications are required to transmit in the 927 to 928 amateur repeater transmit band.

The original configuration of the N6EX repeater employed a TK-931HD radio as the complete transmitter. This high-power version of the radio provided 30 watts of transmit power to the duplexer. The radio power amplifier was slightly modified to handle repeater duty. The capacitors in the power amplifier were replaced with ATC porcelain (B-size) components, the chassis and lid were ventilated to improve cooling, and a fan was mounted directly to the heat sink of the radio.

In March 2006, the repeater was upgraded to include a 90 watt power amplifier. Since the PA required only 1.5 watts input to produce the 90 watt output, the exciter configuration needed to be changed. As part of the upgrade, the TK-931HD was replaced with a modified version of the lower power TK-931. The TK-931, now serving as an exciter to the 90 watt PA, was modified to efficiently provide 1.5 watts drive for the PA.

The repeater exciter functionality and performance is virtually identical to that of the stock Kenwood TK-931, with the exception of reduced output power, slight shift in operating frequency and interface changes necessary for integration into the repeater system.

The majority of the information on the exciter is presented on the Exciter Modification Page. Performance characteristics of the modified exciter are presented on the Exciter Performance Page.

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