On Wed, 29 Jun 2016 20:18:49 +0000 "Poul-Henning Kamp" <p...@phk.freebsd.dk> wrote:
> If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > > The trouble is how to do it without frying the antenna preamp... That's rather "simple". The impedance of the LNA is anything but constant over frequency, said capacitor with the choke are one of those things that make it different than 50 Ohm. You only need to find one frequency at which the impedance is close to a short or to an open and then send down a sine at that frequency and measure the reflection. This is probably easier than doing TDR, but unfortunately it is still quite involved. Another way would be to send down a sine at a known frequency, couple it out at the LNA and inject sharp pulses into the antenna, at the rate of the sine. This way the whole path through the antenna and the LNA down to the receiver can be measured. It even makes it possible to measure the phase differences between different frequencies (think L1, L2). But this would require a custom receiver. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.