ShackBoard v2

The v2 ShackBoard is an active circuit for interfacing one of several types of antenna&preamp combinations to a station receiver. It uses an ADA4930 ultralow noise low distortion driver to receive signals on either or both of two CAT5 transmission line pairs from an antenna unit and delivers them to receiving equipment while substantially maintaining the available signal-to-noise ratio over a very wide range of frequencies from VLF through VHF. It does this while also providing more rejection of unwanted common mode signals than can be obtained with passive circuits. It does this while not introducing significant intermodulation or harmonic distortion even in the presence of high signal levels. This unit can also provides power and control for operating the remote preamplifiers.

Features

  • Provides power and interface for all preamps; PreampA, PreampB & SAPreamp.
  • Very high CMRR
  • low distortion to transfer  SNR present at a preamp to a ham shack receiver
  • Receives one or two pairs of CAT5 RF from an associated preamplifier
  • Approximately 0 dB conversion gain
  • switches on the PCB to allows verifying low CMRR operation of capable preamps
  • may also be used for initial testing of Preamps, Junction Box and cables.
  • Front Connections:
  • SMA: 2 pairs, one pair for each of A and B CAT5 lines
  • Rear Connections:
  • 2.1mm barrel connector for power
  • RJ45 for CAT5 to preamp(s)
  • External supply voltage 10-16 VDC, total current depends upon Preamp selection
  • Double-sided, 4-layer, silk-screen PCBs

    • Two configuration modes are provided, a Utility mode and a Performance mode.

    Utility Mode

    • widest frequency coverage, 300 Hz to 300 MHz usable bandwidth
    • Dual outputs for each A and B CAT5 pair
    • -3 dB conversion gain for each output
    • typically -140 dBm (20nV/rt-Hz) noise floor

    Performance Mode when used with External Combiner

    • lowest noise, typically -154 dBm (4nV/rt-Hz) noise floor
    • Single output for each A and B CAT5 pair
    • 0 dB conversion gain for each output
    • frequency coverage depends upon combiner, 10 kHz to 300 MHz typical


    Testing

    Since assembled PCBs must be ordered with minimum quantity = 2 , this makes a good arrangement for testing. Using each of two PCBs as a simple 50 Ohm <==> 100 balanced line adapter lets transmission through a length cable be measured. Applying power to either of the interconnected boards also allows checking power function of each board.
    DC tests can be performed with a multimeter for power supplies. For RF testing a broadband measurement using a scalar or network analyzer is a very good method. This may be done with a TinySA or nanoVNA. Loss through the system during a two-Shack board test should be near 0 dB. Typically CAT5 cable loss should be about 3 dB/30m at 30 MHz. This PCB may also be used for initial testing of Preamps, Junction Box and cables. 
    There are also switches on the PCB to allow verifying proper preamp performance.

    Since assembled PCBs must be ordered with minimum quantity = 2 , this makes a good arrangement for testing. Using each of two PCBs as a simple 50 Ohm <==> 100 balanced line adapter lets transmission through a length cable be measured. Applying power to either of the interconnected boards also allows checking power function of each board.
    DC tests can be performed with a multimeter for power supplies. For RF testing a broadband measurement using a scalar or network analyzer is a very good method. This may be done with a TinySA or nanoVNA. Loss through the system during a two-Shack board test should be near 0 dB. Typically CAT5 cable loss should be about 3 dB/30m at 30 MHz.

    Use

    In addition to its main function of supplying power to Preamps and receiving differential RF over CAT5 cable and delivering the results to a receiver, this board also has a switch to disconnect the 12V supply from the input circuits of a probe preamplifier while leaving output stages operative. This allows identifying common mode and other unwanted noise ingress apart from the intended balanced antenna. A better method is to simply short the dipole elements but this is not always possible or convenient so simply disabling the input high impedance OpAmps is useful to verify a system.




    Material List

    What you will need to build this hardware

    Item Description

    Provider

    Source Code

    Notes

    Approximate Material Cost

    (excludes setup fees and shipping)

    Assembled ShackBoardv2 PCB

    Download ShackBoardv2 Kit Files

    ==> JLCPCB

    Download ShackBoardv2 Source Files

    ==> KiCad

    		  
    		 US$

    38x88x100mm Clam Shell Enclosure

    eBay
    		Other sources possible. Enclosure needs to accept 84mm wide PCB. US$12

    38x88mm ShackBoardv2 Front Panel

    Download ShackBoardv2 Front Panel Kit Files

    ==> JLCPCB

    Download ShackBoardv2 Front Panel Source Files

    		 Select 'Aluminum" when ordering. These are panels only no components.
    		 US$1

    38x88mm ShackBoardv2 Rear Panel

    Download ShackBoardv2 Rear Panel Kit Files

    ==> JLCPCB

    Download ShackBoardv2 Rear Panel Source Files

    		 Select 'Aluminum" when ordering. These are panels only no components. US$1

    Donations gratefully received

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