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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.
“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:
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
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.
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
S11 (Return loss)
50 MHz -36 dB and 144 MHz -27 dB
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 – “N” RX side. S21 (Isolation)
50 MHz – 86 dB and 144 MHz – 79 dB
7/16 DIN – “N” RX side Engaged – S21 (Insertion Loss)
50 MHz – 0.01 dB and 144 MHz – 0.016 dB
S11 (Return loss), RX side Engaged
50 MHz -38 dB and 144 MHz -28 dB
Relay may be placed in a waterproof plastic case for outdoor use. You can look at our “DS” Plastic box for outdoor use.
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: firstname.lastname@example.org
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 http://www.irts.ie/cgi/showresults.cgi?vhf15.html
to see how we are getting on.
73 John EI2FG”
This presentation is for amateur use only.
73 Goran YU1CF