Recent comments on this topic finally started to focus on one of the weak links in trying to establish meaningful S-meter calibration. That is, the question of the true input Z of the RX. This is ver
There is not 10-20 dB of variation in the S-meter. The worst case mismatch you show is 10+j16. Even this 5:1 SWR only results in a 3 dB mismatch loss, still not much in the overall scheme of things.
I have measured essentially the same thing; not real good but they pass signals. If you look at the schematic, the attenuators are really simple voltage dividers without regard to maintaining any kin
Mismatch loss doesn't apply to this case. The variation was observed with a constant current source, not 50 Ohm source. Power delivered to FT1000 input is R * I ^ 2, where R is the real part of input
Sinisa: I have found your reflector comments useful and interesting. You said, ".. No, it cannot be fixed this way. This will only ensure that constant power is delivered to the external attenuator,
Hi Tod, Thank you. It certainly cannot be fixed that way, although its external manifestation can be masked out. In theory, it could be fixed by redesigning some of input circuits, but I don't think
Sinisa: I think this summarizes things to this point: The following generated a couple of questions. The first question is directed to the last paragraph. I had the impression that the reflected wave
Eric/Sinisa, My calculations agree with Rick's. A constant current source is not a good model of an antenna. An antenna is going to have a finite output impedance - presumeably something close to 50
Once the receiver limits on external site noise coming from the antenna match means nothing for hearing weak signals. That's true with any antenna, including small loops or large Beverages. The only
In fact, it can be shown that optimum noise figure NEVER coincides with a matched condition for bipolar transistors. The ratio of input impedance to source impedance must be approximately equal to t
Not that I want to prolong this thread, but since we don't know what is inside the receiver between the input amplifier and antenna jack none of this means anything. Optimum noise figure might be wi