Cheap High Power 50 / 144 MHz QRO Relay

Cheap QRO Relay 50 / 144 MHz with high isolation

Intended to switch antenna to QRO or preamplifier without need for another isolation relay.

This cheap QRO relay is good enough to protect any sensitive preamplifier. Relay is good for VHF contests and for EME. 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 day task.

How to make it cheap QRO relay 50 / 144 MHz

To make this QRO relay You need: 200W soldering iron to solder 7/16 DIN connectors. 60 – 100W soldering iron to help soldering big surfaces. 30W soldering iron. Basis is 1mm copper 135 x 40 mm. Distance between connectors 40 mm. 

Cheap QRO Relay 50 / 144 MHz with high isolation

 “NC (Normally Connected)” is TX side (7/16 – 7/16 DIN connector). “NO (Normally Open)” is RX side (7/16 – N connector). Relay is energized at receiving. It allows to have same power for preamplifier and relay. Bill of materials: 2 pieces of 0.5 mm copper. Approximate dimensions: 

 These copper sheet are used to shorten central pins and NC pins of relays. Inside view: 

Cheap High Power QRO Relay 50 / 144 MHz

About 35mm UT-141 Teflon cable (RG-402, RG-316). Find it here: RG-402 Coaxial Cable

About 35mm UT-325, EZ-325 or other solid Teflon 8mm cable. Or RG-401 (UT-325 will be better). Find it here: RG-401 Coaxial Cable

2 pieces of Finder 41.61 12V relay: Finder 16 A 12 V Relay or Schrack RT314012: Schrack 16 A 12 V Relay

1 piece Isolation relay Omron G6Z-1PE-A from here or from here.

How does it work?

On transmit side signal passes through 2 pcs 16A relays in parallel to 7/16 DIN connector
On receive side signal passes through isolation relay Omron G6Z-1PEA to Teflon “N” female connector.

Relay Schematic
QRO Relay Side look - YU1CF
Top look (No outside box)
Side look (No outside box)
Side look 2 (No outside box)

How are characteristics measured?

1. HP8753ES Network Analyzer was calibrated Full 2 port.

2. Through calibration was done with N – N barrel.

3. All losses are “barrel losses” + presented data  7/16 DIN – 7/16 DIN TX side.

S21 (Insertion loss)

50 MHz – 0.005 dB and 144 MHz – 0.006 dB

S21 Insertion Loss

S11 (Return loss)

50 MHz -36 dB and 144 MHz -27 dB

S11 Return Loss

7/16 DIN – 7/16 DIN Relay Engaged – S21 Measurements

50 MHz   -17 dB and 144 MHz  -9.5 dB. The only Drawback because of high capacity between contacts.

7/16 DIN - 7/16 DIN Relay Engaged - S21 Measurements

7/16 DIN – “N” RX side. S21 (Isolation)

50 MHz – 86 dB and 144 MHz – 79 dB

7/16 DIN - "N" RX side. S21 (Isolation)

7/16 DIN – “N” RX side Engaged – S21 (Insertion Loss)
50 MHz – 0.01 dB and 144 MHz – 0.016 dB

7/16 DIN - "N" RX side Engaged - S21 (Insertion Loss)

S11 (Return loss), RX side Engaged

50 MHz -38 dB and 144 MHz -28 dB

S11 (Return loss), RX side Engaged

Relay may be placed in a waterproof plastic case for outdoor use. You can look at our “DS” Plastic box for outdoor use.

Cheap High Power 144 MHz 50 MHz 2m 6m Relay - Outdoor

This cheap 50 / 144 MHz relay as seen have very good characteristics adjusted for amateur use on EME and VHF contest. There are no need for another isolation relay. You can connect preamplifier directly.

Like this one: PGA-103+ Wideband Low Noise Amplifier

Or with Band-pass filter: 144 Mhz Band-pass Filter. 

We can make one for you.

32 Ampere contacts are way beyond commercial coaxial relays, and will provide good margin for today’s high power demand. If you are unsure how to make relay do not hesitate to contact me. If you do not have enough time to make relay,  you can contact company “Dual” to make one for you via e-mail:

It is possible to make any combination of “N” male – female and 7/16 DIN male – female of your choice. Just ask for offer.

What others say about Relay. “Goran, we used your high power relays with great success on our recent VHF Field Day with EI9E. See
to see how we are getting on. 
73 John EI2FG”

This presentation is for amateur use only.

73 Goran YU1CF