Halbert.PA@XEROX.ARPA (09/25/84)
Here are some mods for the Kenwood TS-430S I've heard several times on the Kenwood user's net (2000Z Sunday on 14.317). These are by W6EDD. Both are resistor changes on the RF unit. The RF board is accessible from the bottom of the rig. 1. Better noise blanker action: Change R81 from 10K to 22K. Then tune T15 and T16 to achieve better noise blanking. R81 is at the lower right of the RF board between connectors 16 and 7. Look to the left of Q13. T15 and T16 are nearby. The alignment instructions for the noise blanker say to tune T15 and T16 for minimum voltage on R82 (above Q12) while applying a signal at 14.175 MHz at 20db (~6uv) output, and then use less output, as possible. Then use a noise generator, and tune T15 and T16 for minimum audio noise. I didn't have a signal generator, so I just tuned for minimum voltage on R82, and then minimum noise. I used an electrically noisy shaver, and also, fortunately (I'll never say that again), the Russian woodpecker was on, so I could try to reduce it. T15 and T16 don't tune very sharply (though definitely controls the other) so it's a little hard to find the optimum point. But the adjustment does not seem to be terribly critical. I think there was some improvement, most noticeably on the woodpecker. S9 woodpecker gets reduced to S7, and S5 woodpecker goes away completely. 2. Prevent AGC pumping Change R40 from 470K to 30K. R40 is to the right and down from the center of the board, between connectors 15 and 4. R40 is in the AGC control line to the 1st IF amp. I made this change, and didn't really notice any difference, but some people on the Kenwood net praised it, and I have heard a couple of complaints about slightly odd AGC action on the unmodified rig, so this probably fixes that up. --Dan, N6ICX