I would say something slightly different. Firstly I am assuming the PA is on.
It might help to measure the input, especially if it is a valve amplifier. If it is solid state the input match is more likely to be RF power dependent, but if the match is really bad at low power it is not likely to get better at high power and such an amplifier would not be linear. A better way would be to measure at the power you intend to use but that requires a directional coupler. It is not ideal but an SWR meter connected with a very short lead would probably do. If the amplifier oscillates then there is a very high chance of damaging the analyzer, but if that were the case, then at least it did not destroy the rig. Make sure the amplifier output has a wideband matched load - definitely NOT an antenna. I don't think a blocking capacitor would be any use unless there is DC on the amplifier input line. If there is, there is probably a problem. Note: You can use an antenna analyser to initially measure matching circuits of a high power valve amplifier, but only when it is off. You need to load the anode with an appropriate impedance equal to the operational anode output load and tune and load for a good match at the output. It will not be spot on but it should be a good starting point. It is very hard to optimise the tank circuit in a valve PA any other way because of the high voltages both DC and RF. It does not tend to work so well with transistors as the impedances are so low and often dominated by the device capacitance. Mike WILLIS COOKE wrote: > > I would say no to all three questions. The input impedance to the amp > will not be the same when it is not powered and driven. The SWR > indication on the driver will give you some idea of the input impedance. > It should not hurt the antenna analyzer if the amplifier is not powered, > but I don't think it will tell you anything useful. With power on the > amp, it might. > > Willis 'Cookie' Cooke > K5EWJ > > -- View this message in context: http://n2.nabble.com/K3-Dual-Receive-Surprise-tp2211092p2223321.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
