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E8244 signal generator external ALC problems

Question asked by Achrononmaster on Jun 6, 2008
Latest reply on Feb 13, 2009 by dgun
Hi, I'm not sure where to post this question.  Hopefully someone out there will want to help?

I'm looking for a siggen with extremely clean CW power output.  No modulation, just continuous stable power at a fixed frequency.  The range of use required is from 10MHz to 18GHz and max power level of at least 160mW (I only use 10mW, but need to get past a -6dB splitter). 

I'm testing various siggens with and without external ALC.  Currently I have an E8244A on loan, The internal ALC performs reasonably well, but I want to test external ALC as well for completeness.   I have a thermistor mount and 432B power meter with which I'm using the 432B RECORDER output to feedback  to the ext ALC socket.  The trouble is that the E8244 user guide only gives guidance on ext-ALC using a directional coupler and "negative detector"---which I do not have.  What directions I can see indicate that I should use a "Coupling Factor" of 0dB when power levelling with a splitter and power meter.  But I'm not sure what other settings to use.  Everytime I try to switch on RF I either get no power out or an overload.  So I'm doing something wrong, but I'm not sure exactly what needs remedying.  If I want say 1mW at the levelling point (the splitter arm essentially) then what ALC seettings do I need to use other than "External Levelling" and Auto ALC BW and "ALC ON"?

BTW: I've successfully used an 83640 siggen with external ALC.  This instrument has clear instructions on using power meter RECORDER output for ext-ALC, there's a "Levelling Point Power Meter" menu and one can set the Soupling Factor to 0dB and ALSO the "Pwr Mtr Scale" to "10".  The latter option does not seem to exist for the E8244.  There must be something similar I suspect, since it seems that the siggen is simply not interpreting the RECORDER output signal correctly.