Electronics > Repair
Aeroflex IFR-2398 / calibration / repair help
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KJDS:

--- Quote from: andy_silicon on July 01, 2014, 06:13:42 pm ---I'm beginning to suspect a bodge on the input to the 1st mixer.
There is space for a single smd ( probably an R ).
However three components have been soldered to the board in an hf boost filter.
( R in parallel with C and this combination in series with an R )
If the C has gone bad , it might explain the reduced gain and overall HF fall off.
( about 30-40dB down at 2.7G compared to 40Mhz )

--- End quote ---

What value is the R?

It would need to be huge to cause a big drop in gain.
andy_silicon:
At the moment I can't easily see ( it's a vertical stack ).
I'd rather be sure before disassembling it - so will check some other things first.

What does concern me a little is that the mixers are supposed to be +7dBm mixers - and I don't see that level at the LO .
More digging.

At the moment I'm only sure it's between the 1st and 3rd mixer   ::)
andy_silicon:
I think there is at least a problem with the 1st amplifier ( after the pre-amp)
It's supposed to have a gain of 16dB , I'm only seeing 10dB
It's a white 4 pin blob marked 101.
Frequency 3.4ghz , 60mA 4V

I can't find the part number as yet.

Also - I can get the unit to pass the level cal by using the factory menu and setting the value for the expected cal signal level.
So - that would at least seem to indicate the reason for the level cal is purely the gain problem.

I think I've also located the undocumented gpib commands for reading and writing the receiver level correction tables.
There is a correction every 10Mhz from 10Mhz to 2750Mhz.

andy_silicon:
Nearest part I can find is an Agilent ATF-10136
Looks the same - but the gain is potentially a couple of dB lower.

Hmmm.
KJDS:

--- Quote from: andy_silicon on July 02, 2014, 06:10:43 pm ---Nearest part I can find is an Agilent ATF-10136
Looks the same - but the gain is potentially a couple of dB lower.

Hmmm.

--- End quote ---

That gain is specified when matched for optimum noise figure. I suspect that it will be higher matched for best return loss.
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