HV8DC manual

This is a specially designed board to protect up to 8 DC control wires. The connection between the control box and the equipment outside (on the mast) can be dangerous. During a storm, a potential difference can easily arise or voltage can be induced on the control wires - this voltage needs to be safely routed to a common ground potential to protect the equipment behind the protection.

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Product details


Functional description:

The wire from the external environment comes to the terminal and is fed to the high voltage bridge - a thin wire in the function of a fuse. From there it is connected via a capacitor and GDT (75V) to the GND screw. It then goes to the low pass filter and GDT (75V), where it already shares a common GND with the GND terminal on the connector. The low pass filter consists of capacitors and embedded inductance. Behind the LPF is a DC transil with a clamping voltage of about 40V DC, in the opposite way it works as a diode. In parallel with the transil is an LED indicating the voltage on the pin. The input terminal is connected in series with a reset fuse.

CAUTION, IMPORTANT! This board is unlikely to protect your equipment from being destroyed by a direct lightning strike. Minimising the effects of lightning is a more complex problem and requires a more comprehensive approach.

This board is designed to provide surge suppression and additional protection for indoor equipment. If more energy is discharged, this board may be damaged - shorting out the protection element.

NOTE! For proper operation of the protectors, the grounding screw must be connected to a quality grounding point. The connection must be made with the shortest and thickest wire as possible.

hv8dc protection board by qro.cz hamparts.shop

The board contains 8 independent wires for DC control - e.g. to connect the control box and antenna switch, stack match etc. There is also a GND wire - connecting the control box to the outside of the box and a GND screw (Ground ME) to bring the overvoltage to the common ground potential.

The eight control wires can also be split for multiple devices. For example for two Stack Match - 4 + 4 wires and GND or Stack match and 4-to-1 antenna switch. Here is an example:

hv8dc protection board qro.cz hamparts.shop

NOTE! Be careful of the connections to the terminals. Inputs and outputs are the same numbers. So input 1 is output 1. input 2 is output 2, etc.


  • 8 DC control wires
  • Only positive DC voltage
  • DC up to 30V DC
  • Current PTC fuse 0.6A
  • GDT surge protection 75V
  • Transil 40V DC
  • High Voltage bridge fuse
  • RFI low pass filter
  • GDT to GND pin and GND screw
  • LED diode at each CTRL wire
  • Screw terminals
  • DIN rail holder
  • PCB size 135x72 mm

hv8dc protection board block diagram qro.cz hamparts.shop

Product details

Included in package

HV8DC board assembled and tested
DIN rail holders 2 pieces

PCB dimensions (mm) 135x72 mm
Weight brutto (kg) 0.16 kg


Ing. Jan Šustr
ID 05476356, VAT CZ8407024780
Palachova 1777/7, 591 01 Žďár nad Sázavou, Czech republic, Europe

General instructions:

Please also read general instructions before handling the product.

European Union Declaration of Conformity

Manufacturer Ing. Jan Šustr (QRO.cz):

ID 05476356, VAT CZ8407024780
Palachova 1777/7, 591 01 Žďár nad Sázavou, Czech republic, Europe

declares that the assembled product:


is compatible with the relevant Union harmonisation legislation directives:
EMC Directive 2014/30/EU
ČSN EN 61000-6-3 ed. 2
ČSN EN 61000-6-1 ed. 2 (333432)

On behalf of Ing. Jan Šustr (QRO.cz)
Ing. Jan Šustr, CEO
13th January 2024

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