Slater, VE5OA wrote: I have noticed an irregularity on my K2 output.
When setting the power level a 2 watts, and then using the ATU I get a reading on my SWR/power meter in the line of 4 watts. Setting power on the K2 to 3 watts, I get 4 watts on the in line meter. I thought the meter might be faulty, so replaced it with another with the same result. And the ATU gives me a reading of, say 1.3:1, whereas the SWR/power unit shows 3:1. Do I have a problem. If so, how do you suggest I address it? ---------------- To compare your ATU internal SWR metering with an external meter, the external meter must be connected directly to the ATU with a short 50 ohm cable. If you are using an ATU, it must be attached after the external meter. You need a short cable because any residual SWR on the line will cause variations in the readings on a meter only a few inches from the rig, depending upon the frequency where you are running the tests. Even if the SWR meter shows 1:1, there may be enough of a residual mismatch to cause significant error. SWR bridges are fine for showing that the impedance presented to a rig is close enough to 50 ohms resistive for efficient operation, but they are not precision instruments. Ideally, connect your external meter directly to the K2 using a suitable coaxial adapter. Then your SWR and power readings should be similar, although there are usually some variations. Most power meters Hams use - even the over US$100 variety - are seldom closer than 20%. That is, a rig producing 5 watts may show 4 watts on one meter and 6 watts on another. >From your notes, it sounded like you might have one SWR meter connected between the ATU and antenna. If so you cannot get meaningful readings that way. The reason for the ATU is to "tune out" reactance in the transmission line and convert the resulting resistive impedance to 50 ohms to provide the correct load the transmitter. The ATU has no effect on the SWR or impedance of the antenna connected to it. If you put an SWR meter in the circuit between the antenna and tuner it will be seeing impedances it was not designed for and the readings will be very inaccurate. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
