I was doing some research concerning an issue i read on the Repeater Builders List. Seems a ham installed a repeater on 147.760/160 into a building and was receiving a weak signal on the input frequency that was keeping the squelch open. This repeater worked fine when installed in a residence, but it whacked out anytime it was installed in the target location.

Various theories were advanced, and I passed along my observations that some harmonics of the standard baud rates fall exactly on the input frequency. Granted they are like the 10,000th harmonic, but still.

To facilitate my argument, I wrote a script to calculate the various harmonics of the baud rates and print them if they fall on or near the frequency of interest.

In the process of doing this I went ahead and generated a version that swept the 2M repeater subband and noted those harmonics that fell on repeater frequencies.

It seems that 1200 baud is the repeater killer, just look at the harmonics:

Baud Rate: 1200
Upper: 123333
Lower: 121667
I: 121675, F: 146.010 *
I: 121700, F: 146.040 *
I: 121725, F: 146.070 *
I: 121750, F: 146.100 *
I: 121775, F: 146.130 *
I: 121800, F: 146.160 *
I: 121825, F: 146.190 *
I: 121850, F: 146.220 *
I: 121875, F: 146.250 *
I: 121900, F: 146.280 *
I: 121925, F: 146.310 *
I: 121950, F: 146.340 *
I: 121975, F: 146.370 *
I: 122000, F: 146.400 *
I: 122025, F: 146.430 *
I: 122050, F: 146.460 *
I: 122075, F: 146.490 *
I: 122100, F: 146.520 *
I: 122125, F: 146.550 *
I: 122150, F: 146.580 *
I: 122175, F: 146.610 *
I: 122200, F: 146.640 *
I: 122225, F: 146.670 *
I: 122250, F: 146.700 *
I: 122275, F: 146.730 *
I: 122300, F: 146.760 *
I: 122325, F: 146.790 *
I: 122350, F: 146.820 *
I: 122375, F: 146.850 *
I: 122400, F: 146.880 *
I: 122425, F: 146.910 *
I: 122450, F: 146.940 *
I: 122475, F: 146.970 *
I: 122500, F: 147.000 *
I: 122525, F: 147.030 *
I: 122550, F: 147.060 *
I: 122575, F: 147.090 *
I: 122600, F: 147.120 *
I: 122625, F: 147.150 *
I: 122650, F: 147.180 *
I: 122675, F: 147.210 *
I: 122700, F: 147.240 *
I: 122725, F: 147.270 *
I: 122750, F: 147.300 *
I: 122775, F: 147.330 *
I: 122800, F: 147.360 *
I: 122825, F: 147.390 *
I: 122850, F: 147.420 *
I: 122875, F: 147.450 *
I: 122900, F: 147.480 *
I: 122925, F: 147.510 *
I: 122950, F: 147.540 *
I: 122975, F: 147.570 *
I: 123000, F: 147.600 *
I: 123025, F: 147.630 *
I: 123050, F: 147.660 *
I: 123075, F: 147.690 *
I: 123100, F: 147.720 *
I: 123125, F: 147.750 *
I: 123150, F: 147.780 *
I: 123175, F: 147.810 *
I: 123200, F: 147.840 *
I: 123225, F: 147.870 *
I: 123250, F: 147.900 *
I: 123275, F: 147.930 *
I: 123300, F: 147.960 *
I: 123325, F: 147.990 *

Note that every 30 KHz pair is shown as having a harmonic falling on it. hmmm... maybe I've discovered the source of every unattributable mysterious noise source that interferes with a 2M repeater!

Well not really, but it's not hard to visualize thousands of PC's with serial ports, all radiating harmonics. Worth thinking about!

..~Steve>