HELLO
Recently im trying to send signal from a ultrasonic tranciver to a ultrasonic reciver
The problem consist that first i tried this on the protoboard and the thing work properly.
But then i solder everyithing up and the device is not working anymore.
As i can see the problem is on the reciver because the bipolar transistors are amplifing the DC component so the signal witch is some mV is not detected.
The schematich of the reciver is in the attachment
And another think the signal is a 40 kHZ generated from the arduino and amplified to 9 V
Should i put somethink to modulate the signal or else ?
Any help will be great thank you 
The problem consist that first i tried this on the protoboard and the thing work properly.
But then i solder everyithing up and the device is not working anymore.
If the same circuit worked on a proto board, but doesn't work now that you've soldered everything up, then the problem won't be in the circuit design, it will be in your assembly of it.
Or on the proto board did you use a different circuit?
(Capacitive coupling is a good idea, but logic tells me that if it worked previously, it should work now.)
Thank for the response,
I should also mention that if i put the signal directli wired on the input of the reciver the signal is coming out clear with no problem.
Yeah i tried to figur it out where i did the error but it seems that everithing is OK and that is buging me
No, on the proto board it was the same circuit.
The only difference is that, the reciver on the protoboard was supplied with a voltage regulator from 9V to 5V and now is supplied directly from the Arduino 5V outpu.
In your testing, did you use the same source for your transmitter signal? ie The Arduino at 40kHz.
