Symmetrical High Power 50-144MHz Relay

Symmetrical High Power 50 – 144MHz Relay

Intended to switch two equal antennas to QRO. Possible use is as H / V switch.

Although relay will be perfect to switch antenna to QRO and preamplifier. Intention was for switching equal power on “NC” and “NO” sides. On any place where both sides need to pass high power.It has excellent isolation. Good enough to protect any sensitive device on “other” side.But if you intend to use this relay as switch between QRO and preamplifier i suggest to use more simple design described in: You can buy better relay for 5  to 10 times more money, but intention is not to compete with industrial relays.Just homebrew that will do job. This is about 1 – 2 day task. To make this H/V relay you need:200W soldering iron. 60 – 100W to help soldering big surfaces and 30W soldering iron. Basis is 1mm copper 145 x 41 mm.Distance between connectors 55 mm. Although on pictures are unusual combination (input “N” female outputs “N” male it is possible to use any combination of “N” male / female and 7/16 DIN male / female. As usual we will use cheap Finder or Schrack 12V 16A relays. Finder 41.61 12V relay

or Schrack RT314012

Digi-Key configuration – schematics


How does it work? 


Most important is to set all capacitors and inductors. Without inductors signal passes through wires and reduces possible isolation between “NC” and “NO” sides.On every side signal passes through 2 pcs 16A relays in parallel. Open and short circuits enables very high isolation even with that relays with high capacitances between contacts. Copper parts:


Characteristics are measured with HP8753ES Network Analyzer Full 2 port calibrated.NC side:S21 (Isolation)28 MHz – 94 dB50 MHz – 93 dB144 MHz – 76 dB

NC Isolation

S21 (Insertion loss)28 MHz – 0.011 dB50 MHz – 0.018 dB144 MHz – 0.1 dB S11 (Return loss)28 MHz – 33 dB50 MHz -28 dB144 MHz -19.5 dB


NO Side:S21 (Isolation)28 MHz – 89 dB50 MHz – 87 dB144 MHz – 76 dB


S21 (Insertion loss)28 MHz – 0.006 dB50 MHz – 0.01 dB144 MHz – 0.06 dB S11 (Return loss)28 MHz – 37 dB50 MHz -32 dB144 MHz -22 dB


     Finished relay may be placed in a waterproof plastic case for outdoor use.

 Measured characteristics are amazing good. Super high isolation and very low losses enables this homemade relay to be used in any high power demand. This cheap 50 / 144 MHz relay as seen have very good characteristics adjusted for amateur use on EME and HF – VHF.There are no need for another isolation relay. This presentation is for amateur use only.

73 Goran YU1CF