Mercurial > whatever / changeset

--- a/content/eip545b.rst	Wed Dec 20 23:33:53 2017 +0100
+++ b/content/eip545b.rst	Sat Jan 20 15:40:38 2018 +0100
@@ -5,6 +5,8 @@
 :author: David Douard
 :Category: Electronics
 :Tags: test equipment, RF, EIP, 545B, counter
+:series: EIP545B Frequency Counter
+:series_index: 1
 
 
 I recently purchased a broken EIP 545B microwave frequency counter on ebay. It

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/eip545b_2.rst	Sat Jan 20 15:40:38 2018 +0100
@@ -0,0 +1,71 @@
+========================================
+ EIP 545B RF Frequency Counter - Part 2
+========================================
+
+:author: David Douard
+:Category: Electronics
+:Tags: test equipment, RF, EIP, 545B, counter
+:series: EIP545B Frequency Counter
+:series_index: 2
+
+I've started a discussion_ on the `eevblog forum`_ to gather a bit help for my
+project. And I did well since a few fellows did help me a lot on some aspects.
+
+I have now been able to run the power meter at full resolution (even if it's
+very out of calibration), and have been able to locate where these annoying
+default settings are set (tip: unfortunately not in the EEPROM, but in the
+firmware).
+
+I've also digged a bit more for the sensibility problem on band 3. I still
+haven't foudn yet the true culprit, but now I have a few tracks to follow.
+
+I've been in the process of disassembling a part of the firware to look for
+these default settings as well as how to activate the power meter. This latter
+was in fact already activated (but with 3dB resolution, since A107 had no
+U12/CR3 populated).
+
+.. _discussion: https://www.eevblog.com/forum/testgear/eip-545b-frenquency-counter
+.. _`eevblog forum`: https://www.eevblog.com/forum/
+
+
+Power Meter
+===========
+
+While I was waiting for the parts I was missing to modify the A107 as an option
+02 enabled one, I was playing with the counter, and I discovered that the PM
+was in fact already activated.
+
+Obviously, there was no need for the local EPROM (U20) on A107 (with its 2
+companions, U19 and U21) for the EIP454B. I already noticed the address range
+where this EPROM is located on the EIP545A (0x4000) is already filled with
+code/data in the main firmware on the CPU board (A105).
+
+So I added an AD7524 (U12, 8-bit DAC), removed R39 and installed an FH1100
+equivalent (QSCH1245 ie. an HP5082-2835) diode as CR3.
+
+After that, I could read (uncalibrated) power with the expected 0.1dBm
+resolution:
+
+
+.. image:: {filename}images/eip545b/pm_full.jpg
+   :alt: Power Meter at full resolution
+
+*On avance !*
+
+Now I still need to figure how to calibrate the damn stuff... A
+calibration procedure is quickly described in the service manual, but the
+procedure it imply writing the calibration table in the local EPROM on A107.
+Since this is not populated for the EIP545B, it must lay somewhere else.
+
+That's where the magic of the wonderful eevblog comunity shine: HighPrecision_,
+who happens to have serviced these kind of test gears for years, `gave me the
+correct address`_ for the PM calibration table: 0x0810, in the EEPROM.
+
+Much quicker than finding this in the firmware!
+
+Now I need a decent power meter to be able to calibrate it, but one step at a
+time...
+
+
+.. _HighPrecision: https://www.eevblog.com/forum/profile/?u=116109
+.. _`gave me the correct address`: https://www.eevblog.com/forum/testgear/eip-545b-frenquency-counter/msg1400163/#msg1400163

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