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 of High Power 50-144MHz Relay is for switching equal power on “NC (Normally connected)” and “NO (Normally open)” 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 this text. 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 excellent job.

How to make High Power 50-144MHz Relay:

This is about 1 – 2 day task. To make this H/V relay you need: 200 W soldering iron. 60 – 100W to help soldering big surfaces and 30 W soldering iron. Basis is 1 mm copper 145 x 41 mm. Distance between connectors is 55 mm. Although on pictures is unusual combination of connectors it is possible to use any combination of “N” male/female and 7/16 DIN male/female connectors. For instance, we will use cheap Finder or Schrack 12V 16A relays.

You can find Finder 41.61 12V relay here or Schrack RT314012 here. Similarly, you can find Digi-Key relay here.

Mechanical configuration – schematics from Symmetrical High Power 50-144MHz Relay:

Symmetrical High Power 50-144MHz Relay - H/V Switch

How does Symmetrical High Power 50-144MHz Relay – H/V Switch it work?

Relays are not energized. Ham Radio Project by Goran YU1CF
Relays are energized. Ham Radio Project by Goran YU1CF
Montage of Symmetrical High Power 50 - 144MHz Relay

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

Cooper parts for Cheep High Power 6 meter and 2 meter Relay
High Power HV relay back side
High Power HV relay front side

Measured Characteristics using HP8753ES Network Analyzer:

Before the measurement, we performed a full 2-port calibration to make the measurements accurate.

1. S21 (Isolation) measurements and graph – NC (Normally connected) isolation.

Frequency Isolation
14 MHz 100 dB
28 MHz 95 dB
50 MHz 90 dB
144 MHz 75 dB
146 MHz 75 dB
NC Isolation

2. S21 (Insertion loss) and S11 (Return loss)

Frequency S21 S11
14 MHz 0.01 dB – 39 dB
28 MHz 0.01 dB – 33 dB
50 MHz 0.02 dB – 28 dB
144 MHz 0.1 dB – 19.5 dB
146 MHz 0.1 dB – 19.5 dB
NC-Return-Loss

3. S21 (Isolation) measurements and graph – NO (Normally open) isolation.

Frequency Isolation
14 MHz 100 dB
28 MHz 90 dB
50 MHz 87 dB
144 MHz 75 dB
146 MHz 75 dB
NO-Isolation

S21 (Insertion loss) and S11 (Return loss)

Frequency S21 S11
14 MHz 0.01 dB – 40 dB
28 MHz 0.01 dB – 37 dB
50 MHz 0.01 dB – 32 dB
144 MHz 0.06 dB – 22 dB
146 MHz 0.06 dB – 22 dB
NO-S11

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

You can find link to outdoor plastic box here.

Symmetrical High Power 50-144MHz Relay in Outdoor plastic box

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 has 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.

If you are not sure if you can make it you can order from us via e-mail: info@antennas-amplifiers.com

73 Goran YU1CF