On 3/17/2025 2:36 PM, Bob McGraw wrote:
Now the reason for stressing known good 50 ohm load, I have 3 different brands, and power dummy loads. Although all say "50 ohms" they are not! One is 57 ohms (air type load), one is 48 ohms cold and 53 ohms hot (Cantenna) , and the third is 50.5 ohms (Bird 100 watt load).
Great advice. There are "dummy loads" and precision dummy loads. I own about seven, two of which are VERY high precision for calibrating my vector network analyzer well into the UHF range, and rated for about 1 W. The others are professional loads, intended for use with transmitters. One is rated 500W continuous, and I saw its twin on the bench where my KPA1500 was been tested under load. The others are rated for lower power. All of those transmitter loads measure within 1% cold, and all of the transmitting loads were bought for pennies on the dollar at ham flea markets.
A dummy load is a precision resistor, constructed in such a manner that parallel capacitance and series inductance are quite small, so a rough measurement of its precision, especially at low HF, can be achieved with a high quality, high precision, and well calibrated Ohmmeter.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
