2022-P-063 | RX Galvanic Isolator + Protector + Limiter (1 MHz - 400 MHz)

Function

Optimized for HF Band (2 Mhz -> 60 Mhz) Limits input RF ! You can keep your TX antennas in close proximity! Common mode noise rejection when used directly at the receiver input. Protects receiver input from ESD or input power damage !

Science

We designed this especially to protect a sensitive receiver front-end against high levels of RF and ESD discharges. This multi-stage design includes a gas discharge tube for maximum ESD protection, high pass filter and rectifier diode as a first stage RF clipper and ESD protection. A MMIC limiter is used limit the RF input (max 32 dBm) to a maximum of 8 dBm at the output. The 1:1 transformer is used to reject common mode and RF strays and provides a galvanic isolation between the receiver and the antenna input.

Placement advice

As close as possible (direct on the connector) on the receiver input.

Datasheets

• Frequency Range: 1 MHz through 400 MHz
• Insertion Loss: < 1dB above 3MHz, 1.23dB on 1.9 MHz (160M band)
• VSWR: < 1.6 above 3 MHz (2.28 on 160M band) (see measurements)
• Common mode rejection: +-10dB rejection on HF ! High rejection > 25dB on the 40M, 80M and 160M band
• Less than 8 dBm on the output. (most modern receivers (FlexRadio, Airspy, Icom) can handle these and even more!!!)

Measurements

• Reterun Loss VSWR HF 
• Insertion Loss HF 
• Common mode Rejection HF 
• Return Loss VSWR VHF 
• Insertion Loss VHF 

Bill of materials

• 1x RF.Guru PCB
• 1x Female SMA connector Antenna
• 1x Male SMA connector (screw connector) RX
• 1x RF shield frame
• 1x RF shield cover
• 1x Mini Circuits ADT1-1+
• 1x Mini Circuits RLM-521-2WL+
• 1x Enclosure
• 2x Screw

Assembly

An assembly video will be available in the future.

The first thing to solder is the transformer (ADT1-1+), the dot on the pcb matches the dot on the transformer. The easiest way to solder the transformer is to first put some tin on one of solder pads on the pcb. Whilst pressing down onto the transformer use the soldering iron to melt the tin again and align the transformer, solder al other legs to the PCB. The same goes for the RLM-521-2WL+. The solder the SMA connectors, we advice to start with the center pin (signal) to get it alligned.