![]() ![]() Although an optimum filter for repeater receive operation would be centered around 902 MHz, the easiest filters to obtain are centered at 915 MHz. To handle the frequency change, both filters must be replaced. The original filters were centered at 938 MHz to cover the intended 935 to 941 receive range. The filters, on the other hand, have a + 12.5 MHz bandwidth. The LNA transistor is specified over a fairly wide frequency range, so there is no problem operating in the 902 band. The front-end of the TK-931 consists of a three-pole dielectric filter followed by a low-noise amplifier transistor (2SC4093) followed by an additional 4-pole dielectric filter. ![]() Connection of Audio/COR board to the radio.Areas of modification (highlighted in yellow) include: This photo shows the inside of the modified TK-931. Gene provided much of the initial modification information. Many thanks to Gene Colson (W7UVH) for help in getting the Kenwood radios going. Check-out and alignment of the receiver after modification is recommended. It also assumes that the receiver portion of the radio was properly operating in its original frequency range prior to modification. This is accomplished using the Kenwood KPG-5D programming software and KPG-4 programming cable, or equivalent. Not shown here is the effort required to program the radio for the desired operating frequency. This page identifies all the hardware modifications necessary to adapt a Kenwood TK-931 transceiver for 902 MHz repeater receive operation. ![]()
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