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Posted: 24 Jul 2020, 17:54 

FWIW, i have accomplished a "proof of concept" by successfully decoding "something" using an RF capture i made with a LimeSDR (USB version).
https://ready.cs.washington.edu/~tandersn/ruckusframe.jpg

This process required nothing too complicated. Following internet instructions for installing LimeSDR on ubuntu, then ld-decode on ubuntu, and using "pothos flow" (a visual SDR block flow tool) to capture an rf file. Happycube added the compatibility for the file type (float32, thanks). I only have "broad strokes" knowledge of all the concepts, so it could only improve from here. This setup can be obtained with zero soldering. EDIT: [I did have to remove one component from the limesdr board to improve HF performance, this can be done with a screwdriver]. I bought everything, hooked it up, and fiddled with the GUI settings of Pothos Flow for the SDR until i saw something in the ~7Mhz range. https://ready.cs.washington.edu/~tandersn/pothosflow.jpg

While i realize for an actual archive capture, you would want to use the domesday duplicator board, for doing comparisons and tests, or to get your feet wet, this setup might provide a means to do that. the "domesday duplicator" is better and will provide the most fidelity, but this is an "off the shelf" solution that is available to anyone hesitant to put together the board.

I believe that the LimeSDR *may* be overkill at this point, because there are now cheap off the shelf frequency multipliers (shifter?) available (https://airspy.com/spyverter-r2/). Using such a device, you could use a cheaper SDR, and then just divide the signal in pothos flow.

DISCLAIMER: I can not confirm yet that this is a "full working solution". The "Ruckus" disc is in horrible shape, nothing in the setup has been optimized. I think that the capture the picture above is taken from, doesn't have a strong enough signal in the EFM, and possibly the analog audio.

Anyone reading this that has SDR knowledge, let me know. I literally just fiddled around with things until i got something ld-decode would accept. When i raised the gain past ~43 for the SDR, the signal actually disappeared!

Tony

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Posted: 26 Jul 2020, 19:11 

The V2600 is really a CLD-S201 with a serial port. If you get a good deal on it and it's fixable, it's still nice :)

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Posted: 30 Jul 2020, 17:15 

Had this happen to my dreamcast psu. If you're handy with a soldering iron then it shouldnt be too difficult to repair. I would suggest scraping back the trace to copper and solder a thick piece of copper across the break. I usually strip a coax and use the copper. Epoxy the board before you solder for added strength.

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Posted: 25 Aug 2020, 22:58 

Titan91,

I was waiting for someone more knowledgeable to respond, and they can correct me if i am wrong.

While the spec says the highest frequency is 9.31Mhz (or whatever it is), happycube once told me you needed about ~12.5Mhz of bandwidth, minimum, for the captures. I don't know why that is the case, but that is what i recall (iirc).

Nyquist-Shannon states the minimum, but that is the minimum with the most quantization noise/error. You can't go with the 10 bit 14.4MSPS mode, because it isn't high enough. period. So that leaves you the 2 8 bit modes. The higher msps will get you less quantization noise/error, so i'd go for that.

Just make sure your disk is fast enough to save it.

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Posted: 10 Oct 2020, 02:54 

I've been playing around with modifying the cx288n boards to improve performance. I have achieved some pretty significant results i think. Second opinion wanted. this is currently suboptimal, because the low pass filter i am using is too low, and is cutting off the higher frequencies i want (but it is what i had on hand). The terminator is 75ohm instead of 50ohm, because again, it was what i had on hand. I believe i have found, and i have ordered, a better low pass filter here: https://www.minicircuits.com/pdfs/BLP-10.7+.pdf <-- that is the inline BNC one, but they also make one you would have to solder onto the board or make a casing for, that is less than half the cost of the BNC one.

This started by realizing there was a CVBS frequency low pass filter built into the boards, this would adversely affect the capture of signals over 6mhz. I removed them on 2 of my boards, and noticed a big improvement, but also a big difference still between the boards. Upon investigating and tracing the signal path, i discovered that board (A) has very little circuitry from the starting point to the CX chip. Board (B) had a "switch" IC that allowed the card to route different inputs to different locations around the board, one being the CX chip. I then started thinking about bypassing that chip, then i had the idea, to just bypass everything. There is now only a 100nf DC blocking cap between where i soldered my lead and the CX chip. I removed the components on the other side, so the signal wouldn't go anywhere else. The card is modified with a BNC connector.

https://ready.cs.washington.edu/~tandersn/nobackup/card.png

I used a BNC cable/t connector/terminator/low pass filter.

https://ready.cs.washington.edu/~tandersn/nobackup/lpf.png

I achieved 42db s/n ratio with this capture
https://ready.cs.washington.edu/~tandersn/nobackup/bb10mhz10fsc.png

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Posted: 20 Oct 2020, 23:58 

For anyone that is contemplating mod'ing the cxadc card as i have done, this is the LPF i used with the Video Essentials and Beauty and the Beast samples: https://www.minicircuits.com/pdfs/SXLP-13+.pdf I have not done "thorough" testing with this, this is just what i used. I have also this purchased: https://www.minicircuits.com/pdfs/SXLP-10.7+.pdf which will probably work better for PAL LDs. I'm not doing tape captures, so not sure what LPF would work for that, but maybe this one: https://www.minicircuits.com/pdfs/SXLP-5+.pdf

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Posted: 10 Nov 2020, 01:11 

There's more than one way to skin a cat! on trying to obtain 40msps from my cx card, i decided to go another route: replace the timing crystal.
root@:/laserdisc# ./mydd 40mspscrystal2.r8
^C1768+0 records in
1767+0 records out
926416896 bytes (926 MB, 884 MiB) copied, 23.1788 s,** 40.0 MB/s**

root@:/laserdisc# ld-decode 40mspscrystal2.r8 out/40mspscrystal2
file frame 1 CAV frame 15345
file frame 2 CAV frame 15346
file frame 3 CAV frame 15347
file frame 4 CAV frame 15348
file frame 5 CAV frame 15349
file frame 6 CAV frame 15350
^CTerminated, saving JSON and exiting
10fsc now= 50msps:
root@:/laserdisc# ./mydd 50msps10fsctest.r8
^C3133+0 records in
3132+0 records out
1642070016 bytes (1.6 GB, 1.5 GiB) copied, 32.8782 s, 49.9 MB/s

root@:/laserdisc# ld-decode 50msps10fsctest.r8 out/50msps -f 50
file frame 0 CAV frame 23684
file frame 1 CAV frame 23685
file frame 2 CAV frame 23686
file frame 3 CAV frame 23687
file frame 4 CAV frame 23688
file frame 5 CAV frame 23689
file frame 6 CAV frame 23690
file frame 7 CAV frame 23691
file frame 8 CAV frame 23692
file frame 9 CAV frame 23693
file frame 10 CAV frame 23694
file frame 11 CAV frame 23695
file frame 12 CAV frame 23696
^CTerminated, saving JSON and exiting

this is the crystal i used: https://www.mouser.com/datasheet/2/115/FL400WFQA1-1129572.pdf

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Posted: 15 Nov 2020, 01:18 

I think you may still have the onboard LPF in the mix.

Good find on the interference though!

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Posted: 24 Nov 2020, 20:10 

I am still "fine tuning" my setup, but things are steadily improving. Currently, the setup is (all coax is rg174):

1. 4300D (uncalibrated, but supposedly "new in box" when i bought it, and appeared as such)
2. tapping RF off of pickup rather than internal RF test point (avoids 90s era amplification circuitry)
3. inline 50ohm (51 actually) resistor
4. pre made OPA657 amplifier board with manual gain adjustment: LINK mounted in a project box, SMA connectors removed, coax attached to board, and to BNC connectors. Powered with 6 "AA" batteries in 2 3x holders: LINK
5. an inline 20ohm resistor (should probably be higher ohm, the amp amplifies a lot, and is easy to overload the ADC)
6. 13+mhz low pass filter from mini circuits: link coax connected to BNC connectors so it is removable.
7. BNC "T" connector and 50ohm termination ( i like to have the option to remove it, but could be integrated into modified card)
7. Capture card, PCIe CXADC card: LINK which is modified, removing onboard LPF, onboard 75ohm termination, BNC port added where one of the RCA jacks was, wire connecting to the DC blocking cap on the circuit board for the S-Video input. 28.636mhz crystal replaced with 40mhz: LINK for 40msps capture without driver modification.



Things i am still investigating:
1. using alternate (10.7+) LPF
2. improved connection to PCIe board (get closer to chip pin to reduce exposed trace, which can pick up interference)
3. my short captures are better than long ones at same settings, indicating maybe a heat sink is needed?
4. update the driver to do 40msps without changing crystal (progress made, but S/N is poor).

For those that "only have a laptop" would be interesting to know if something like this works: mini pcie to pcie


Chapter 33 of ggv1069:
https://media.discordapp.net/attachments/666555924185350154/780850978411905074/unknown.png

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Posted: 31 Jul 2021, 18:07 

I've been working on a "No Solder Setup" using the CX card. I've got fairly decent results with the following:

USD $10 HD CCTV BALUN
https://www.amazon.com/gp/product/B07TBWJB53
USD $11 SMA to BNC (need 2x sma male to bnc female)
https://www.amazon.com/Coaxial-Adapter-Female-Connector-Pieces/dp/B07T8LMHHQ
USD $8 BNC cable
https://www.amazon.com/BNC-Male-RG316-Cable-Inches/dp/B07MB89Z7R
(shortest you can live with)
USD $5 BNC 50ohm terminator
https://www.amazon.com/CESS-Coaxial-Connector-Adapter-Terminator/dp/B01ASF5D6M/
USD $6 BNC T Connector
https://www.amazon.com/Splitter-Connector-Double-T-Shape-Adaptor/dp/B06XHFGVXM
USD $7 3x AA battery holder with switch
https://www.amazon.com/Onwon-Pieces-Battery-Holder-Storage/dp/B07M8HTQ3F

USD $23 OPA657
https://www.ebay.com/itm/272936368386
USD $8 5db attenuator
https://www.ebay.com/itm/184973161399

USD $25 PCIe BNC CX card
https://www.aliexpress.com/item/4001286595482.html

USD $36 mini circuits BLP-10.7+ low pass filter
https://www.minicircuits.com/WebStore/dashboard.html?model=BLP-10.7%2B

Total without tax and shipping: $139

if you can solder you can save $20 making your own low pass filter (which is shown in the picture below):
USD $14 mini circuits sclf-10.7+
https://www.minicircuits.com/WebStore/dashboard.html?model=SCLF-10.7%2B

DISCLAIMERS:
A) There seems to be as much as a 2db SNR difference between CX cards, even of the same make and model. I've gotten the best results with cards ending in '3' or '1'.
B) My laserdisc player has not been calibrated yet, so SNR could improve if it is not optimally set now.
C) The level adjuster on the OPA657 is not the best value it could be for this use case (5k ohm). As such, the effective range you want to use is roughly 0 - 15%. If you go higher, the amplitude actually starts to go back down again.
D) To use this setup, you set the gain on the 657 knob while playing the strongest part of the disc (go to end of disc, play it, use leveladj and the opa657 knob to get leveladj at about 1 or 2), then go and start the capture.
E) I use a python script that adjusts the CX card gain in real-time while capturing CAV discs (which probably could be improved).

This is the setup, however in this picture, i am using a SCLF-10.7+ that i made instead of BLP-10.7+ and BNC cable.
https://ready.cs.washington.edu/~tandersn/nobackup/1280xno_solder.jpg.jpg
https://ready.cs.washington.edu/~tandersn/nobackup/1280xno_solder_2.jpg

The battery packs must be wired like this for the amp (not shown in picture above) to have -4.5/0/+4.5:
https://ready.cs.washington.edu/~tandersn/nobackup/batterieswired.png

This is the GGV1069 full disc readout from this setup (this is using the BLP-10.7+ and short BNC cable NOT the SCLF-10.7+):
https://ready.cs.washington.edu/~tandersn/nobackup/BlueCX3_NoCapNoTerm_8fsc_Balun_opa657_5db_blp107+_ex50t_ggv1069.PNG
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