At 1/15/2009 07:51, you wrote: > > I did see a reduction in desense when I replaced the multiplier type > > exciters with the PLL exciters. > > > > 73 - Jim W5ZIT > >Yup... > >The biggest advantage of the GE VHF PLL is the reduction in side-band >noise over the standard phase-modulated multiplier type. On a typical >600 kHz two meter split, 22 dB of side-band noise reduction is afforded >with the use of a PLL exciter. How? Any fundamental oscillator has >inherent noise. When this oscillator is multiplied in frequency, so is >any noise or frequency shift. While the crystal oscillator is >elementary low in noise, in a GE VHF exciter the crystal gets multiplied >12 times, and so does the amount of fundamental noise.
For the techy types, the amount of noise increase due to multiplication is 20*log(N) dB, where N is the multiplication factor. So for x 12, the phase noise would be 21.6 dB higher than that of the xtal oscillator. For x 36 (UHF exciter), it's 31.1 dB. I don't suppose G.E. ever made a PLL exciter for the MVP? Bob NO6B
