new QTH, new antenna...

Printable View

11-30-2012, 05:10 PM
K8YS

new QTH, new antenna...

we moved, so my tower is back at the old house, the new house is towerless -- damn! indeed!

I've been thinking on an OCF dipole. Reports/reviews are positive. I am going to add a wrinkle to this by adding an Icom AH-4.

I planned on a OCF dipole using 88 feet on one side, 47 feet on the other. A center insulator (dog bone) and feed the thing woth 450 window line. Then down about 40 feet to the AH-4, mounted on the chainlink fence.

The major issue here is the run of 450 ohm ladder line. I have not been about to find any references to anyone else doing this.

The new house has TREES! == BIG TREES!

Any suggestions from the antenna guru's here??
11-30-2012, 05:33 PM
X-Rated

Quote:

Originally Posted by K8YS

we moved, so my tower is back at the old house, the new house is towerless -- damn! indeed!

I've been thinking on an OCF dipole. Reports/reviews are positive. I am going to add a wrinkle to this by adding an Icom AH-4.

I planned on a OCF dipole using 88 feet on one side, 47 feet on the other. A center insulator (dog bone) and feed the thing woth 450 window line. Then down about 40 feet to the AH-4, mounted on the chainlink fence.

The major issue here is the run of 450 ohm ladder line. I have not been about to find any references to anyone else doing this.

The new house has TREES! == BIG TREES!

Any suggestions from the antenna guru's here??

Can you map your trees and mark their heights?
11-30-2012, 09:30 PM
KJ3N

Quote:

Originally Posted by K8YS

we moved, so my tower is back at the old house, the new house is towerless -- damn! indeed!

I've been thinking on an OCF dipole. Reports/reviews are positive. I am going to add a wrinkle to this by adding an Icom AH-4.

I planned on a OCF dipole using 88 feet on one side, 47 feet on the other. A center insulator (dog bone) and feed the thing woth 450 window line. Then down about 40 feet to the AH-4, mounted on the chainlink fence.

The major issue here is the run of 450 ohm ladder line. I have not been about to find any references to anyone else doing this.

Any suggestions from the antenna guru's here??

This was an AH-4 feeding an 80m loop via 450 ladder line.

http://forums.qrz.com/showthread.php...50#post2478550

Just strap the ladder line across the lug on the ceramic post and the ground lug on the other side. Done.
11-30-2012, 11:30 PM
K8YS

that is what I did at the old house, but I made a multiband dipole. I needed to limit the copper running through the air here so that is why the OCF.

At the old house, I had a 40 ft tower, an arm coming off at the top of the tower, and the dipole on the end of the arm. I cam down to ground level to the AH-4. I split the window/ladder line and one side to the ceramic insulator and the other to the wing nut side...

The only difference will be that I have major (old growth) trees where I will launch paracord into the trees. On the end of the paracord, tie off to a dogbone.

One issue I might have is stretching the copper over the years. Copper-weld wont stretch, but the #14 bare that I plan to use might. As I type this, I just might change out the soft copper for the copper-weld.
11-30-2012, 11:33 PM
K8YS

Quote:

Originally Posted by X-Rated

Can you map your trees and mark their heights?

thats an idea! map them, know exactly where they are - too much work for the right now... until then, I will continue to use Google Earth.
11-30-2012, 11:59 PM
KJ3N

Quote:

Originally Posted by K8YS

that is what I did at the old house, but I made a multiband dipole. I needed to limit the copper running through the air here so that is why the OCF.

Strictly speaking, the only reason to use an OCF is to be able to match the antenna on several bands using coax. Since you're feeding the antenna with ladder line, there's really no reason to do anything other than the standard dipole. Just make sure you have enough length for the lowest band you plan on operating.

Quote:

The only difference will be that I have major (old growth) trees where I will launch paracord into the trees. On the end of the paracord, tie off to a dogbone.

I would tend to use UV resistant Dacron rope. Many ham stores sell it. My favorite size to use is 3/16 diameter. It's got plenty of strength and holds up very well.

Quote:

One issue I might have is stretching the copper over the years. Copper-weld wont stretch, but the #14 bare that I plan to use might. As I type this, I just might change out the soft copper for the copper-weld.

It's not going to make that much difference if the copper stretches. The AH-4 will simply adjust accordingly. As a matter of tensile strength, the copper-weld is certainly more durable.

I used to make my 80m dipole with stranded copper from places like Home Depot, but the soft copper kept breaking every 6-9 months. The current 80m dipole is made with copper-weld and has been up for over 4 years now.

Oh, and using bare wire as opposed to insulated isn't going to make than much of a difference. I've always used insulated.
12-08-2012, 10:10 PM
N1LAF

For wire, I use copper clad steel from Wireman

"Fabricated 14 AWG solid copper clad steel (30%). The best choice for long-lived, high performance antennas in any environment. Breaking strength 550 lbs. fabricated and coiled on large diameter reels to retain a 'memory' of close to straight for easy assembly, it does have a bit of a 'mind of its own', making it somewhat tough to work with, but well worth the effort as the best propagator and longest lived."
http://thewireman.com/antennap.html

My dipole, 270 feet in total length, has been up for 10 years (one leg came down during Sandy, pulled out of the insulator - did not break, now back up in the air).
Highly recommended.

The other is ladder line length.

From my notes on ladder line lengths:
From MFJ tuner manual....
1. Never center feed a half-wave multi-band antenna with a high impedance feedline that
is close to an odd multiple of a quarter-wave long.

2. Never center feed a full-wave antenna with any feedline close to a multiple of a halfwave
long.

3. If a tuner will not tune a multi-band antenna, add or subtract 1/8 wave of feedline (for
the band that won't tune) and try again.

4. Never try to load a G5RV or center fed dipole on a band below the half-wave design
frequency. If you want to operate an 80 meter antenna on 160 meters, feed either or
both conductors as a longwire against the station ground.

To avoid problems matching or feeding any dipole antenna with high impedance lines,
keep the lines around these lengths. The worst possible line lengths are shown in
brackets:
160 meter dipole; 35-60, 170-195 or 210-235 feet. (Avoid 130, 260 ft)
80 meter dipole; 34-40, 90-102 or 160-172 feet. (Avoid 66, 135, 190 ft)
40 meter dipole; 42-52, 73-83, 112-123 or 145-155 feet. (Avoid 32, 64, 96, 128 ft)