Combining RX pins

I have 2 arduinos performing completely different tasks that I want to operate at the same time. I want both of them to receive the same signal from the same USB wire, and I only want one of them to send data back to USB.

I figured to do this, all I'd need to do was bridge the RX pins on both arduinos, but that doesn't seem to do anything. I'd prefer not to do softwareserial when I'm looking to use a signal that already exists. Besides, serial transmissions do affect the speed of the program so I'd rather not slow it down by using the software serial library.

Did you remember to provide a common Ground between the two Arduinos?

I figured to do this, all I'd need to do was bridge the RX pins on both arduinos, but that doesn't seem to do anything.

Did you connect the grounds?

but that doesn't seem to do anything

The other thing to consider is the1K seriese resistor in line with the RX data. You might have to remove this on the second arduino to disconnect it from the USB chip.

Yes, I did connect the grounds. I even connected the VIN on the 2nd arduino to the 5v on the first one.

I tired using a transistor to amplify the signal so the resistor wouldn't be a problem, which didn't help. Besides, how would I go about removing that resistor without permanantly damaging the board?

I even connected the VIN on the 2nd arduino to the 5v on the first one.

That was a mistake, Vin needs to be about 7.5V in order for the regulator to work. You should connect the 5V of the powered arduino to the 5V of the unpowered one.

I tired using a transistor to amplify the signal so the resistor wouldn't be a problem, which didn't help

Just one transistor will invert the signal you need two.

Well, I didn't keep the VIN as it was anyway because I'd prefer not to distribute power like that. But why 7.5v? USB supplies 5v, and IIRC the USB power source is connected to VIN.

Anyways, how would I go about doing 2 transistors? Should I do it like this:

5v-----Ca RX1---Ba Cb---5v Ea-----Bb RX2----Eb

Where RX1 is the arduino connected to USB and RX2 is the one leeching off its data.

EDIT: As another note, I tried connecting TX from the "host" arduino to an LED and watched it blink whenever that arduino would send data back to USB. However, if I tried connecting RX to an LED, it would just stay somewhat dim and not pulse at all whenever data would be received.

But why 7.5v? USB supplies 5v, and IIRC the USB power source is connected to VIN.

No it is not. Vin is connected to the on board 5V regulator, so you need 1.5 above the output voltage in order for it to work correctly.

That arrangement for two transistors is a Darlington pair and will not solve the inversion problem. Just use two common emitter circuits cascaded.

Yes that is what the LED will look like if you connect it between the RX and ground. This is because the default state of the line is high and it goes low for data. Therefore it is always on and occasionally goes off. This is almost impossible to see. Connect it the other way round, LED anode to +5V, cathode to resistor, resistor to RX.