In addition to Vic's "spot on" comments, Bird elements, like any precision device, need to be checked and calibrated regularly if they are to be depended upon.
In commercial shops we at least compared several from time to time to be sure they all agreed with each other and, if not whether it was the element (usually the case) or the meter that was at fault. They went to a calibration lab for adjustment every year or two. The elements can be thrown out of calibration by being bumped around in the tool box, where too many of them hang out when not in use. After dropping an element, most users stick it back in and, if it registers power, heave a sigh of relief thinking "it wasn't hurt". Hmmmmm.... The most accurate method most Hams have of measuring RF power is to use a rectifier/voltmeter combination. That's because the accuracy of the peak voltage measurement is dependent upon a DMM that the Ham uses regularly and which can be easily checked with decent accuracy in a number of ways. For power levels beyond the limit of the metering circuit a simple voltage divider such as the Elecraft DL1 uses can be pressed into service. If you aren't sure about the accuracy of the divider, run a test at a power level that you can measure both directly and through the voltage divider to confirm its accuracy and, if there is an error, determine the needed correction. As for the MFJ guy who dismissed the Bird meter, he may have gone to the same sales seminars I attended in the 1970's. The one where they teach you this: Your prospect says, I have a Whiz-Bang unit!" The salesman looks genuinely interested and say, "Oh, really? Which model?" You say, "It's the mega-plex Mark Five!" He shakes his head slowly, saying, "Oh...that model...is it still working?" Nothing like the "inferred condemnation". Ron AC7AC _______________________________________________ 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
