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EIP 545B Frenquency counter
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douardda:
Thanks a lot for all these informations...

0x0810 was on the list of possible "culprits", but I was not near a definitive conclusion yet. Quite a time saver!


--- Quote from: HighPrecision on January 14, 2018, 10:41:03 am ---Special WB68 is a BAND 3 Low end frequency extension to 0.6GHz (600MHz) with reduced specs for sensitivity and power meter dynamic range.

Frequency offset and resolution setting have not to do with this special option, in the EEPROM there are saved the instrument power-on defaults.

--- End quote ---


I noticed I could go quiter lower the 1GHz on band 3, haven't thought it might be thanks to the WB68 special version.


--- Quote from: HighPrecision on January 14, 2018, 10:41:03 am ---As I said the power meter calibration is NOT part of the standard calibration procedure, there is no related TEST xx for this.

The EEPROM on CPU board is allocated from 0x0800 to 0x0FFF

Power meter calibration table start at 0x0810

YIG DAC calibration table start at 0x0C00, but I have no idea if the special option WB68 start at this location (shifted data ?).

--- End quote ---


I had these ones from the service manual, yes. And it does not look like the location has moved somewhere else.


--- Quote from: HighPrecision on January 14, 2018, 10:41:03 am ---You can use TEST 10 to modify the EEPROM locations, or via GPIB with TA10 command, obviously the write-protect switch should be disabled.

I suggest to save the entire EEPROM before any attempt to change data.

--- End quote ---

I already have dumped the whole memory: EPROM + EEPROM (which I will make available on my blog as soon as I have time to write part 2), which is what I've disassembled (the hard part being to locate the constant/data areas... for now, I still have many places where the disassembled code is just garbage due to a CONST area not properly handled).

But no way I enter the calibration values using TEST10! :-)


Another question, maybe I missed this in the service manual, but is there a procedure to check wheter the YIG calibration is correct?

I was thinking about how I can check this (to address my sensibility problem), and I'm not sure what's the best way of doing this verification.

Don't think I can force the YIG to stay centerered at a given freq, without scanning (then inject a know signal and measure the power ouput from A203. Can I? Setting the low/high freq limits to the same value maybe?

David
 
edpalmer42:

--- Quote from: douardda on January 14, 2018, 10:41:41 pm ---Another question, maybe I missed this in the service manual, but is there a procedure to check wheter the YIG calibration is correct?

I was thinking about how I can check this (to address my sensibility problem), and I'm not sure what's the best way of doing this verification.

Don't think I can force the YIG to stay centerered at a given freq, without scanning (then inject a know signal and measure the power ouput from A203. Can I? Setting the low/high freq limits to the same value maybe?

David

--- End quote ---

I had to go digging to find it.  It's been 5 years since I did this.  It's in Section 7 of the manual and it's called "Converter Calibration".  My unit started out with a sensitivity of ~ -19 dBm @ 1 GHz.  It was so far out of adjustment that the adjustment procedure didn't work.  I did more digging and I've got a couple of pages of notes that I can transcribe if necessary.  I ended up with a sensitivity that matched the spec of -30 dBm up to at least 11.5 GHz.  That's the highest frequency I could generate.

Ed
HighPrecision:

--- Quote from: douardda on January 14, 2018, 10:41:41 pm ---Another question, maybe I missed this in the service manual, but is there a procedure to check wheter the YIG calibration is correct?

--- End quote ---
A quick method only to verify if the YIGF is correctly centered, is to inject a small bipolar current into feedback node of U3 OP-Amp on A108 board, in example: a potentiometer between +12V and -12V, the wiper connected with a reasonable high value resistor in series to the (-) input of Op-Amp.
douardda:

--- Quote from: HighPrecision on January 15, 2018, 04:08:06 pm ---A quick method only to verify if the YIGF is correctly centered, is to inject a small bipolar current into feedback node of U3 OP-Amp on A108 board, in example: a potentiometer between +12V and -12V, the wiper connected with a reasonable high value resistor in series to the (-) input of Op-Amp.

--- End quote ---

Thanks a lot. Pretty obvious once one does look at the schematics of the YIG driver... I'll give a try ASAP.

David
HighPrecision:

--- Quote from: douardda on January 16, 2018, 11:35:00 pm ---Thanks a lot. Pretty obvious once one does look at the schematics of the YIG driver... I'll give a try ASAP.

--- End quote ---
This test is intended to be done in 'search mode' of the counter (no signal detected) for lowest power level to start count, counter firmware execute a fine tune of the YIG filter at first signal acquisition.

Another weak point maybe the YIG current sense resistor (the big one on A108) is out of tolerance.
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