On Oct 25, 2:50 pm, "Joel Kolstad"
wrote:
Thanks again Tom, you've really cleared things up for me here.

Here's the concrete numbers... in the center of the band, S22 -- converted
back to an impedance -- is 119.5-j90 ohms. With a 2V source, if I conjugate
match my 50 ohm load obviously I get 1V across the resistor or 20mW = 13dBm.
Without a match... let's see... current around the loop is 2/(119.5-j90+50) =
9.2+j4.89 mA, and power in the 50 ohm load is I^2*R = 3.04+j4.5mW = (looking
just at real power) 4.83dBm. So... without a match... I'd be leaving 13-4.83
= 8.18dB of gain "on the floor"... ouch!

---Joel

OK, things aren't quite as bad as you've painted them, Joel. Given the
analysis you did for the second half, what you need to do for the first
half is to look at the power delivered to 119.5 ohms with 1 volt across
it. That's 1/119.5 watts, or about 8.4 milliwatts. That's about
+9.23dBm That's the maximum power you can get from that source. Into
50 ohms with no matching, the magnitude of the current is 10.42mA.
The resistor does NOT care what phase angle relative to your arbitrary
reference that is. So the power in that case is 5.43mW, or +7.35dBm.
You've left not 8dB, but just under 2dB, of gain "on the floor."
Things don't get really bad till the mismatch is quite a bit worse than
that. Note that your 2dB occurs with an SWR of about 4:1. At 2:1 SWR,
you only lose half a dB.

Cheers,
Tom