Is my SAW-bird broken?

[Miguel Ríos Martín]

Hello.

I suspect my NooElec SAWbird+ H1 amplifier might be faulty or not amplifying enough. I measured it with the NanoVNA SAA-2N V2.2 and got a gain of only S21 = 7.8 dB (powering the module via USB). I've attached the measurement graph.

Does anyone have any idea if it could be faulty? The LED turned off a while ago, but I have the feeling it's been losing gain.

Is there an alternative to this module? This is the second one that's given me problems, and it's currently unavailable on Amazon and the NooElec website.

Miguel.

[Alex P]

Miguel,

Did you add 40 dB of attenuation from the VNA into the SAWbird to prevent overdriving 

 and a DC block on the LNA 'input' SMA to prevent DC backfeeding the VNA ?

This is a typical setup.

Alex Pettit

[Miguel Ríos Martín]

Sorry, I'm new to all this.

Is it necessary to include the DC block and 40 dB attenuator in the circuit for measurement?

I've directly connected CH0 to input and CH1 to output.

I don't quite understand; I thought measuring S21 in a circuit without those components would be sufficient. Could you explain it to me, please?

Miguel

[b alex pettit jr]

The SAWbird has an internal gain of + 40 dB .. 

Try again with the attenuator ...if you drive the amp into saturation you will get 'low gain'

===============================================

Alex Pettit

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[Sweet Thing]

I will bring my HP  noise figure meter with me to Green Bank conference,  or you cannot wait  send to me for measurement up  in WV by the Potomic;   qth on ,,QRZ  at  W8YCM

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[Miguel Ríos Martín]

Thank you very much, but I won't be attending the Green Bank conference and it's too far away for shipping.

[Sweet Thing]

What is your location?

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[Miguel Ríos Martín]

Pamplona, Spain

[Jan Lustrup]

Remember the sawbird outputs +5V on the output connector, so use a Bias T or DC blocker when testing with a VNA as it has a 50 Ohm resistor on tit’s input.

Jan

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[Miguel Ríos Martín]

Just so I'm clear: Should I put the DC block at the Swabird's output? I ask because in the photo, the block and the 40 dB attenuator are placed at the Swabird's input.

[b alex pettit jr]

You are Correct .. although it worked, the Proper Setup  is