900MHz Cable Feeds

The obvious question is: how much loss can you *stand* in this application? (X-posted to more appropriate groups)

to

hardline might work. quite expensive.

i'm not sure what the losses from the connectors would be in a hardline system.

Gravity

Hello Joe,

If both ends (or at least one) are terminated with line impedance there should be no reflections. Losses will be listed in the cables specs. There should be a graph, losses per meter versus frequency, or at least a table that contains losses at 1GHz. If frequencies that high aren't listed you need a better cable. If there are no loss specs at all don't even consider buying the cable.

Let's say you arrive at 3dB which would be kind of high for 20 meters. That would tell you that half the transmitted energy doesn't arrive at the other end and that your SNR would be 3dB worse than if the receiver had been directly connected to the antenna.

Thanks,

Why is the SNR 3dB worse?

JG

Hello Joe,

When the cable loss is 3dB then the signal received at the antenna will drop by 3dB before it reaches the receiver. The receiver's noise performance, however, will remain the same unless it's mismatched.

If the other station had a similar cable added you'd lose a total of 6dB because its transmit energy would have dropped by 3dB before reaching its antenna.