Wed, 13 Mar 2024 11:03:13 +0100
Update URLs for pcb & firmware to sourcehut
74 | 1 | ======================================== |
2 | EIP 545B RF Frequency Counter - Part 2 | |
3 | ======================================== | |
4 | ||
5 | :author: David Douard | |
6 | :Category: Electronics | |
7 | :Tags: test equipment, RF, EIP, 545B, counter | |
8 | :series: EIP545B Frequency Counter | |
9 | :series_index: 2 | |
10 | ||
11 | I've started a discussion_ on the `eevblog forum`_ to gather a bit help for my | |
12 | project. And I did well since a few fellows did help me a lot on some aspects. | |
13 | ||
14 | I have now been able to run the power meter at full resolution (even if it's | |
15 | very out of calibration), and have been able to locate where these annoying | |
16 | default settings are set (tip: unfortunately not in the EEPROM, but in the | |
17 | firmware). | |
18 | ||
82 | 19 | I've also digged a bit more for the sensitivity problem on band 3. I still |
74 | 20 | haven't foudn yet the true culprit, but now I have a few tracks to follow. |
21 | ||
22 | I've been in the process of disassembling a part of the firware to look for | |
23 | these default settings as well as how to activate the power meter. This latter | |
24 | was in fact already activated (but with 3dB resolution, since A107 had no | |
25 | U12/CR3 populated). | |
26 | ||
27 | .. _discussion: https://www.eevblog.com/forum/testgear/eip-545b-frenquency-counter | |
28 | .. _`eevblog forum`: https://www.eevblog.com/forum/ | |
29 | ||
30 | ||
31 | Power Meter | |
32 | =========== | |
33 | ||
34 | While I was waiting for the parts I was missing to modify the A107 as an option | |
35 | 02 enabled one, I was playing with the counter, and I discovered that the PM | |
36 | was in fact already activated. | |
37 | ||
38 | Obviously, there was no need for the local EPROM (U20) on A107 (with its 2 | |
39 | companions, U19 and U21) for the EIP454B. I already noticed the address range | |
40 | where this EPROM is located on the EIP545A (0x4000) is already filled with | |
41 | code/data in the main firmware on the CPU board (A105). | |
42 | ||
43 | So I added an AD7524 (U12, 8-bit DAC), removed R39 and installed an FH1100 | |
44 | equivalent (QSCH1245 ie. an HP5082-2835) diode as CR3. | |
45 | ||
46 | After that, I could read (uncalibrated) power with the expected 0.1dBm | |
47 | resolution: | |
48 | ||
49 | ||
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Fix several inter-document links
David Douard <david.douard@sdf3.org>
parents:
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changeset
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50 | .. image:: {static}/images/eip545b/pm_full.jpg |
74 | 51 | :alt: Power Meter at full resolution |
52 | ||
53 | *On avance !* | |
54 | ||
55 | Now I still need to figure how to calibrate the damn stuff... A | |
56 | calibration procedure is quickly described in the service manual, but the | |
57 | procedure it imply writing the calibration table in the local EPROM on A107. | |
58 | Since this is not populated for the EIP545B, it must lay somewhere else. | |
59 | ||
60 | That's where the magic of the wonderful eevblog comunity shine: HighPrecision_, | |
61 | who happens to have serviced these kind of test gears for years, `gave me the | |
62 | correct address`_ for the PM calibration table: 0x0810, in the EEPROM. | |
63 | ||
64 | Much quicker than finding this in the firmware! | |
65 | ||
66 | Now I need a decent power meter to be able to calibrate it, but one step at a | |
67 | time... | |
68 | ||
69 | ||
70 | .. _HighPrecision: https://www.eevblog.com/forum/profile/?u=116109 | |
71 | .. _`gave me the correct address`: https://www.eevblog.com/forum/testgear/eip-545b-frenquency-counter/msg1400163/#msg1400163 |