[R-390] Signal Generator Impedence Questions

[Bill Hawkins]

It's true that if you measure the input in microvolts then
the impedance doesn't matter. But the low impedance puts a
load across the antenna coil that isn't there if you use a
long wire antenna. The purpose of the network was to simulate
the antenna and not load down the antenna coil.

As it is, most people aren't set up to do microvolt tests
because their shielding isn't good enough. Might just as
well connect the generator direct to the antenna and do
the alignment without worrying about impedances. You'll
use the antenna trimmer with a real antenna.

You can't really test the receiver sensitivity that way,
though. You can check your shielding by seeing if the jump
in dB from 1 microvolt to 10 is the same as 10 to 100.

If your generator has a microvoltmeter, it may be looking at
the input to the attenuator, which has to be properly
terminated to have the right voltage at the output.

Bill Hawkins