mack@mlokai.DEC (12/03/85)
If I can't get some help, it looks like I'll be off the air for the winter. Help! I live on the second floor of a 3-story building. The entire second floor is my apartment. The woman I am renting it from lives upstairs. I live in the city of Lawrence in a neighborhood with a lot of big Victorian houses all practically on top of one another. Our "yard" consists of a 7 foot by 10 foot plot of grass. The landlady grows vegetables in a single row in what was once a flower border next to the house. The problem. We moved here in September. My mother was supposed to send me the TA33-Jr that my father had (K1BSB, now silent key), but due to shipping costs, she sold it and sent money instead. This was in late October. We have a 18AVT trap-vertical, but nowhere to put radials. We bought a nice ICOM rig last summer, and would like to be able to use it this winter. Just as an experiment, in early October, I attached my longest radial to my antenna tuner and tried tuning it up. I started at low power, cranked it up a little (about 40 Watts), and got a nice RF burn off the control knob. (Minor problem -- forgot about a ground system.) There is a nice place directly below my shack window for a ground rod, but its about 15 feet down. Is that too long for a ground wire? Unfortunately, my shack window is fairly close to the place where the power comes into the house, so I can't run a dipole around the house with the feedpoint at the shack window. Does anybody have any good ideas for an antenna for this situation? Ralph Mack WA1ZCH
stephany.WBST@Xerox.ARPA (12/05/85)
Antenna problem: A good ground can be made by running more than one wire of different lengths to the ground stake. The reasoning is that is one of the wires is a multiple of a quarter wave, one of the other wires will not be and will short it. A good ground should be the first criterion for any ham installation. I would suggest a folded dipole for your antenna. It has the advantage of : (1) it is balanced and does not depend upon a good ground, (2) it is horizontal and can be strung inside a room or attic, (3) fits a wide range of impedances. Many years ago I strung a 20 meter folded dipole across a room and worked the world including antartica. The thing was made of TV 300 ohm line 10 meters long and was strung through two rooms and supported with rubberbands and nails. It was center fed. The part of the antenna oppocite the feed point was brought out to two aligator clips. shorting these clips gave 20 meters. Clipping to a piece of 300 ohm line about 2 feet long (cut to get good resonance) gave 15 meters. A coil scramble of hookup wire gave 40 meters. I dont remember what I used for 10, I think I left it open. But this was in a home on a hill. Your location is the most important factor in the DX you get, not the antenna. Joe N2XS
taylor.WBST@Xerox.ARPA (12/05/85)
IT SOUNDS LIKE YOU HAVE A CRYING NEED FOR A GOOD SERIES-TUNED LOOP ANTENNA. I WOULD START WITH ABOUT 50 FEET OF LARGE DIAMETER CONDUCTOR IN A LOOP. FEED THE "NEAR" END AND RETURN THE "FAR" END THROUGH A WIDE-SPACED VARIABLE CAPACITOR-- ABOUT 50 PF. MAX. FOR 75 METER BAND. ~1800 PF. MICA CAPACITOR ACROSS THE FEED POINT WILL HELP THE MATCH. GOOD LUCK! JIM (W2OZH)
taylor.WBST@Xerox.ARPA (12/05/85)
SOUNDS LIKE YOU HAVE A CRYING NEED FOR A SERIES-TUNED LOOP. I HAVE BEEN VERY SUCCESSFUL WITH THESE ON 75. I WOULD DRAPE ABOUT 50 FEET OF LARGE DIAMETER CONDUCTOR (THE OUTER CONDUCTOR OF GOOD RG8/U COAX IS FINE). FEED THE "NEAR" END AND RETURN THE "FAR" END TO THE FEED-POINT GROUND THROUGH A WIDE-SPACED AIR-VARIABLE CAP (~50PF. MAX. FOR 75 METERS). ~1800 PF. MICA ACROSS THE FEED-POINT HELPS ON THE MATCH. GOOD LUCK! JIM (W2OZH)
KWILLIAMS.ES@Xerox.ARPA (12/05/85)
Get the R-3 vertical. It is expensive but well worth it for your situation. It is a half wave and has a motor driven coil and needs no radials. I believe it is made by cushcraft. Kent AA6P