kl7aj
04-30-2007, 09:18 PM
It is a lovely Spring day, perfect for some antenna work. #Dorf Underfelt, ID0NT, decides to repair a run of coax to his 80 meter inverted vee, high on a hill above his house, that he hasn't been able to use since last November. #He had buried almost three hundred feet of surplus double-shielded RG-8-like coax nearly a decade earlier. #It was a tremendous bargain at the time, and still will be, if he can repair the thing in a reasonable amount of time. #It has been overgrown with roots and berry bushes in the intervening years, and Dorf dreads traipsing through the woods digging up 300 feet of the stuff to find a potential flaw in the cable. #
Dorf has a better idea. #He returns to his shack, and connects the input of his questionable transmission lint to the input of an oscilloscope via a coaxial tee. #He feeds the output from an R.F. signal generator through a 10k series resistor into the other port of the T connector.
He then slowly sweeps his R.F. generator from 500khz to 30 MHZ, watching the R.F. waveform on the oscilloscope as he goes along. #He notices a sudden dip in the waveform voltage at 2.3 MHz. #He notices another, less pronounced dip at 4.6 MHz. #He thinks he has the problem solved, but just for good measure he continues sweeping. #To his chagrin, he notices another dip at 7.9 MHz. #
With a sigh, Dorf heads out to the woods with a root axe and a shovel. #What will Dorf find?
Eric
Dorf has a better idea. #He returns to his shack, and connects the input of his questionable transmission lint to the input of an oscilloscope via a coaxial tee. #He feeds the output from an R.F. signal generator through a 10k series resistor into the other port of the T connector.
He then slowly sweeps his R.F. generator from 500khz to 30 MHZ, watching the R.F. waveform on the oscilloscope as he goes along. #He notices a sudden dip in the waveform voltage at 2.3 MHz. #He notices another, less pronounced dip at 4.6 MHz. #He thinks he has the problem solved, but just for good measure he continues sweeping. #To his chagrin, he notices another dip at 7.9 MHz. #
With a sigh, Dorf heads out to the woods with a root axe and a shovel. #What will Dorf find?
Eric