...or for a single band, instead of using ground rods, use a fair ground radial network at the far side. Len SM7BIC
-----Ursprungligt meddelande----- Från: Topband [mailto:[email protected]] För Tom W8JI Skickat: den 28 november 2012 16:58 Till: Martin; [email protected] Ämne: Re: Topband: Beverage question > So, how to measure the bev? Is this procedure correct: > The bev is ~8 feet above ground. The far end is open, not grounded, no > resistor. > The analyzer connects directly to the bev and the ground rod at the rx > end through its bnc-to-banana plug adaptor . Measure and note the > impedances for 160, 80, (40, 30m). Calculate the mean average. > Calculate and install a transformer to match that value to the feedline. > At the far end, find the value for the termination resulting in a flat > swr-curve over the range 1.5Mhz - 10Mhz. > Correct? There are two ways to do this: 1.) measure the impedance peaks and the impedance minimums and take the geometric mean of the adjacent peaks and minimums and average them. This is almost certainly the least accurate method. 2.) measure the SWR variation with frequency as you adjust termination resistance. The resistance that gives the minimal variation with frequency (using a continuous sweep, not band by band) will be the proper termination. In all cases, be sure you have reasonably good grounds. Several spaced rods or a few short buried radials and some rods will generally work, ground resistance only has to be less than 50 ohms or so. _______________________________________________ Topband reflector - [email protected] _______________________________________________ Topband reflector - [email protected]
