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Antennas / Re: 40 and 80 meter wire dipoles... How far apart?
« on: July 12, 2013, 08:20:33 AM »
You didn't note or I do not see what you plan on using as feedline. EITHER METHOD YOU CHOOSE WHY NOT USE ONLY ONE FEEDLINE FOR BOTH ANTENNAS? Attach at the apex of each and run the legs as far opposing each other as you can. Saves the cost of another run of coax and the antennas take care of which length to use as you change bands; tune each individually as you would if there was only one antenna. I would tune the 40M then the 80M - but either should work since the close proximity to the earth will come into play.
If you use coax - you best use or at least consider using a 1:1 CURRENT balun at the apex. Then simply connect the 'legs; of each dipole to each side of the BALUN and RUN THE COAX straight down the tower to a point where it can "turn" and go to your shack.
If using OPEN WIRE / LADDER LINE AS FEEDLINE (instead of coax) --- be sure to use "standoffs" to keep it away from the tower and other metal objects by one to two feet if possible. As with the coax - run the feedline straight down the tower - turn at the appropriate place and run to the shack. NO BALUN at the FEEDPOINT - but rather use one just prior to ENTRY INTO THE SHACK where you would make the transition from LADDER LINE FEEDLINE to A SHORT RUN OF COAX TO THE RIG.
If you are 'gutsy' and have a tuner with a balun installed you could run the LADDER LINE through the wall, into the shack and put the CURRENT BALUN just before the first connection point at the tuner. KEEP STRAY RF from wandering around the rig and accessories and biting the heck out if your lips and other tender parts. I'd keep the balun OUTSIDE the shack and run the shortest coax jumper as possible to the rig.
Do at least consider using ONLY ONE FEEDLINE --- no need for the second if the connection at the apex is the same. I run a 80M / 160M combo this way - using coax and it works great in spite of the 160 being WAY to close to the ground. Your 80 will likely be a NVIS for the most part - but it will serve you well.
73 Don / WD5JOY
Old Senile Don - Today is a "good day"!
If you use coax - you best use or at least consider using a 1:1 CURRENT balun at the apex. Then simply connect the 'legs; of each dipole to each side of the BALUN and RUN THE COAX straight down the tower to a point where it can "turn" and go to your shack.
If using OPEN WIRE / LADDER LINE AS FEEDLINE (instead of coax) --- be sure to use "standoffs" to keep it away from the tower and other metal objects by one to two feet if possible. As with the coax - run the feedline straight down the tower - turn at the appropriate place and run to the shack. NO BALUN at the FEEDPOINT - but rather use one just prior to ENTRY INTO THE SHACK where you would make the transition from LADDER LINE FEEDLINE to A SHORT RUN OF COAX TO THE RIG.
If you are 'gutsy' and have a tuner with a balun installed you could run the LADDER LINE through the wall, into the shack and put the CURRENT BALUN just before the first connection point at the tuner. KEEP STRAY RF from wandering around the rig and accessories and biting the heck out if your lips and other tender parts. I'd keep the balun OUTSIDE the shack and run the shortest coax jumper as possible to the rig.
Do at least consider using ONLY ONE FEEDLINE --- no need for the second if the connection at the apex is the same. I run a 80M / 160M combo this way - using coax and it works great in spite of the 160 being WAY to close to the ground. Your 80 will likely be a NVIS for the most part - but it will serve you well.
73 Don / WD5JOY
Old Senile Don - Today is a "good day"!