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Message ID: 675     Entry time: Mon Sep 12 01:21:39 2011
Author: Frank 
Type: HowTo 
Category: VCO 
Subject: temporary VCO solution 

thought a little bit about how to create the difference of 127MHz. Here are two ways how we can do this right now:

We only use one AOM (as before). We can't use the second one as we would have to use it way beyond it's operating range (which we already tried Friday) or in second order where we don't get enough light if double passed.
So using only one we have the following options:

  1. we use the Isomet 19" 80MHz OM driver which can be tuned down to 63.5Mhz using an external voltage. The frequency tuning knob can't go that low.
    We know that the phase noise is very high and the output signal is not even close to a sine wave. So this is OK for alignment but i would not use that for an actual measurement without detailed noise characterization.
  2. we get one of the Marconi's from the 40m and use our 2W RF amplifier which we already used Friday. The phase noise is is very very low and we don't need a lot of tuning range, so it's even better.
    This guarantees that we don't sit on the phase noise of the VCO even if we only have a low UGF for the second loop.
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