is that for 0dB attenuator setting? the level should change with attenuator setting.
still it doenst necessarily mean you dont have the second LO but it could be one reason for very low IF output
is there a connector for 50MHz going into the RF module as I described in E4402B? i suspect there must be a similar structure in there
if that is the case then you can disconnect it and check if the 50MHz exists on that coaxial and also you can inject 50MHz from outside
(on E4402B it was -15dBm I recall)?
there is probably a connector that brings 800MHz REF into the RF module (to generate the LO) as well
you should check that too. on E4402B it is 600MHz because the freq plan is completely different...
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On Sat, Mar 30, 2019 at 04:56 PM, Michael Williams wrote:
You raise a valid point.? On that point, I decided to double check the magnitude of the 21.4MHz IF signal coming out of A8J3.? It is present, but is around -67 dBm ¨C far lower than it should be.? ?Earlier, I had simply checked for the presence of a signal at that point using my oscilloscope, and did not do an actual level measurement.
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Apologies for providing incorrect info ¨C this stuff is hard enough without the wrong info!
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Cheers,
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Mike
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if you have the second IF out put at correct amplitude the of course your second LO is fine
so the only culprits is either the divider chip (800 / 16) or the solid state switch that injects the 50MH to the RF path
and disconnects the input
i am not familiar with E4401B and I am sure it is different than the rest of the ESA series
but you might find this helpful if you have the block diagram. Based on my experience with E4402B
there is a connector (MMCX or SMB I dont remember) that feeds the 50MHz into the RF module (before the switch)
first of all do you have the 50MHz in that coaxial wire? (assuming it exists!)
second, you can disconnect it and inject a clean 50MHz -15dBm (from external RF generator) to that point
and then run the calibration and see what happens. I have done that on E4402B...
On Sat, Mar 30, 2019 at 02:13 PM, Michael Williams wrote:
Hi Jon,
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Yes, I see an IF signal coming out of A8J3 when I follow the RF verification procedure when using an *external* 50 MHZ source.? The signal does very with attenuation, as describe in the service guide.?
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-- Mike
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Can you see a 21.7Mhz IF signal on the cable plugged into A3J2?? I was looking over pages 55 - 75 of the ESA Service guide for a E4401B and there is a verification process to check on RF deck function.? I only suggest this because your original message stated your seeing signals but wasn't sure if they were as expected in Amplitude and correct frequency.??
On Saturday, March 30, 2019, 12:58:42 PM CDT, Tom B <tbryan@...> wrote:
Did you make sure the cal signal was turned on?? You can turn it off on the E4401B.
On 3/30/2019 1:39 PM, Michael Williams wrote:
Hi Mark,
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Thanks for the reply and the thoughts.
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From the info in my CLIP, the 50 MHZ CAL signal is generated by dividing the 800 MHZ 2nd LO by 16.? The 2nd LO gets its power from the TEST MUX (U56).? This mux is dead ¨C no enable signal, no activity on any of the control lines.? That¡¯s where I¡¯m stuck, I can¡¯t figure out if it¡¯s a hardware or software issue that is causing the 2nd LO to not get turned on.? The CLIP is not very clear on what tells the fractional divider (U55) to enable it.
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The 10MHz reference clock is the timing source for the 800 MHZ 2nd LO, and is present, both internally and at the 10MHZ output connector in the back.
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Thanks again,
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Mike
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