RF Capture Hardware

Previous Page Hardware Installation Guide

What are we looking for?

This is a sub-doc about ADC's & SDRs that can be used for the decode projects this list includes standardised and validated methods and workflows and new options.

You can help expand this list via posting on the Discord, Sub-Reddit or Emailing Harry directly.

Format Divide

There are 3 Types of FM RF encoded analogue media.

Single Channel or single path/test point of tapping. Audio & Video alongside timecode is all in one modulated track but separate carriers, such as LaserDisc, Video8, Hi8 and BetaMax NTSC.

Duel Channel, such as VHS, BetaMax PAL, and others ware the Video RF and HiFi RF are 2 separate RF paths or test points after the head amplifier and tracking stage.

Duel Video Channel, such as W-VHS, BetaCam & BetaCam SP with 2 channels for Video RF and 1 channel for HiFi Audio + 2x Channel baseband for Linear Audio.

Note

Older VHS & Betamax have Linear audio only, which requires a standard line-level audio ADC, Umatic, SMPTE-A/B/C and older formats only have Linear audio.

The Technical bit

The input frequency range required for most of the signals from HiFi to CVBS video is 1Mhz to 10Mhz at least, this can go upwards of 30Mhz for MUSE RF.

2msps = 1 Mhz of Bandwidth

So most archival class solutions today will be based around the 28-40msps minimum range sampling wise, of course this is wholly format dependent with HiFi RF requiring less then 10msps.

Other factors such as input LPF (low pass filters) makes common SDRs a very mixed viability for straight to file and onto decoding with ease.

Standardised

This is the list of devices that ware fully tested and are in active use.

CX Card

CX Cards Doc

28.6msps 8-bit / 40msps 8-bit / 54msps 8-bit (upto 57msps on some cards)

FM RF capture via the CX Card method has been further improved with external amplifiers.

Amplifyers

(Current) ADA4857 Dual Channel Amplifier	(Old) AD8367 AGC Amplifier

ADA4857

The dual channel ADA4857 IC based amplifier board is has been designed to work well with the high impedance output from the VCR head amplifiers, ideal for CX Card based Clockgen Mod setups with stock 75ohm termination providing fixed gain amplification with 2 channels for Video RF and HiFi RF.

ADA4857 KoFi / ADA4857 PCBway

AD8367

Note

The AD8367 is no longer recommended as the input termination is internal to the IC, making it hard to modify to suit and match impedance for a VCR and the default 200ohm is often not optimal on all decks, if having issues please use the ADA4857 instead.

Caution

The AD8367 boards are 3-5v range only if voltage is 6-12v+ a buck boost converter or regulator to lower the voltage will be required. Jumper configuration in automatic gain mode "AGC" is both pairs with jumpers as shown in image.

AD8367 Pot-less AliExpress Link / AD8367 with Pot AliExpress Link / 4.5v AA Battery Holder / Wiki Setup Link

Duel Synchronised ADC CX Cards "Clockgen Mod"

Clockgen mod simplified wiki

Software Defined Crystal Rate
Hardware Synchronised Multi-Card Capture
Hardware Synchronised Linear/Baseband Audio Capture

The most advanced mod available today, using an external crystal to generate the clock source we can have drift free capture with 2-4 CX Cards and audio feeds.

This allows duel channel video formats such as Betacam to be captured, or Video FM + HiFi FM + Linear for many other formats like VHS or Betamax.

Possible thanks to cxadc-clock-generator-audio-adc By Rene Wolf

External crystal timing via 2 additional PCB boards, a Jig with an SMA and Mainboard has allowed for under 50USD multi card sync, using 2 or more CX Cards alongside a extra input for synchronised Linear/Reference audio capture also has a extra input for headswiching timing signals.

Raspberry Pi Pico as the interface and control board.
Adafruit Si5351A for generating the shared clock source with 5 potential inputs.
PCM1802 ADC for L/R input Linear/HiFi audio capture.

Audio inputs and head switch input is on a dedicated bracket you can 3D print.

Clock Speed & Audio is controlled by Alsamixer.

Synchronised capture from all devices is done via scripting.

DomesDay Duplicator (DdD)

DomesDay Duplicator Docs

40msps 10-bit

DE0-Nano FPGA / FX3 USB 3.0 Board

TI ADS825 ADC
OPA690 OP-AMP
Selectable 4 Position DIP gain control

RTLSDR

RTLSDR Wiki Page

Used for HiFi-Decode

Pictured Order: TNC Male to SMA Male / TNC Female to SMA Male / BNC Male to SMA Male / BNC Female to SMA Male / Nooelec RTL-SDR v5

Currently Being Standardised

MISRC - Multi Input Simultaneous Raw RF Capture

Formerly called adc_usb3 / SMIRF - Simultaneous Multi Input RF Capture. - DD86 Discord

GitHub / GitHub Wiki

Price estimates PCB: 20-30USD / Parts 100-150USD (Global Direct Fab Pricing)

Features:

Simple Firmware Flashing & CLI Capture app
Real-Time FLAC compression support
CVBS RAW capture support
Tang Nano 20k FPGA (buffer) + MS2130 RAW HDMI Data capture
External Clock Source Output
6 Extra Aux inputs for audio ADC modules etc
Duel ADC / Duel Input
Physically adjustable input filters
2 Channel 12-Bit, 40msps sampling (upto 65msps with IC replacement)
AD8138 Driver, Op-Amp / SN74ls541 Buffer / AD9235 ADC

Revision	Image	Notes
1.0		Base development version.
1.5		Updated BOM and BNC/SMA pads for RF inputs.
2.0		Added 1x PCM1802 and 2x RCA for L/R audio inputs DIPs modifyed.
2.1		Added 2x PCM1802 and 4x RCA for duel L/R audio inputs, DIPS restored to orignal to confrom PCB size.