Richard H McCorkle wrote: > Hi Samuel, > > I suggest starting by downloading the component level information for > the 53131A and 53132A from tha Agilent site at the following links. > > http://cp.literature.agilent.com/litweb/pdf/5989-6308EN.pdf > http://cp.literature.agilent.com/litweb/pdf/5989-6307EN.pdf > > The 53132A document includes a schematic of the channel C board with > parts list and may assist in getting you started.
I see that they have a factory select resistor that unbalances the input slightly to keep the prescaler from oscillating with no input. This a simple, obvious "solution" to this problem. It is also non-optimum, for three reasons. It desensitizes the prescaler, it uses a factory select part that may not work consistently over temperature, and it still results in a range of input power where the counter displays garbage. In the 5334B C channel, I used a diode detector that turned on the counter at a repeatable input power. Thus you never got garbage on the display due to low input power. The detector used the well known circuit where you bias the diode on with a few 100 microamps of DC and have a compensating diode that is not excited by RF. A difference amp subtracts the compensating diode voltage. Simple, but effective. It is also interesting to note that in 1987 I used the MB506 prescaler. Here they have simply upgraded to the MB510. Not likely to be any better on noisy sources. Rick Karlquist N6RK _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
