Re: [CQ-Contest] awesome upgrades to the 8 band vertical!!

[Bill Coleman <aa4lr@mac.com>]

On Apr 30, 2004, at 7:38 AM, Hanlon, Steve wrote:

> I am in the process of putting up a 50' tower and am looking for some 
> advice.  my plan is to put an A3 on top with wires for 40m and 80m.  i 
> enjoy SSB contesting and hope to get to the point of CW contesting.

Steve, I set up a similar station just a couple of years ago. I have a 
few words of advice.

First, I'd recommend you get the 40m add-on for the A3S, provided your 
tower installation can take the extra wind load ( < 1 square foot ), 
unless you have higher supports available than the 50 foot tower 
itself. A 40m dipole at 50 feet should show some directivity, although 
the angles supported are somewhat high -- good for domestic contests.

I've been using a 1/4 sloper off the tower at 42 feet. It's better than 
the 80m dipole I have at 35 feet, but doesn't really cut it during 
crowded contest conditions. I plan to add the 40m adaptor soon.

Second, I recommend you set your A3S half-way between the CW and Center 
settings. This it the K7LXC recommendations for the 40-2CD, but I've 
found they work well on the A3S. SWR curves are good from near the 
bottom of the band to near the top. You do sacrifice some gain in the 
phone portion, but the general pattern remains clean over a very wide 
range.

> should i cut the wires for 40m and 80m to the center of the band to 
> work both modes or should i have dipoles for each mode for each band?

The 40m dipole can be cut a tad toward the CW side (like 7080-7100 kHz) 
and should cover most of the band well. On 80m, you might want to 
consider an OWA cell to give you wider coverage.

Me, I have the 1/4 wave sloper for 40m, and a 80m doublet cut for 
somewhere near the middle. I use an auto-tuner with each.

The key to these dipoles is height above ground. If you have trees and 
can get the 80m dipole 70 or higher, it will be a good performer on 
both 80m and 40m with a tuner. If you use a tuner and open wire, the 
length of the dipole is no longer critical, and any length from 140 to 
80 feet will work (provided the tuner can give you a match)

If, like me, the tower is your highest support, you can use 1/4 wave 
slopers, or try to shunt-feed the  entire tower on 80m. (This works 
about as well for me as the low dipole, but I really need more radials)

>   i'm only running 100 watts from the 746PRO and it has a built in 
> tuner to "tune" the dipoles.  i'm not sure what the cost of going for 
> the center of the bands will be in terms of power loss.

The loss here doesn't occur in the antenna, but in the feedline. What 
are you using as a feedline for these dipoles.

> i am also looking to put up a sloper for 160m using the design in the 
> ARRL wire antenna book.  it uses 90 turns at the top of a 40' tower 
> with 63 or so feet sloping to the earth.

Sounds like a shortened 1/4 wave sloper. The performance of this 
antenna will be greatly improved by adding ground radials to the tower.

> any suggestions would be helpful - i'm tired of the stick in the mud 
> vertical with S7 noise levels.

I have an R7000 about 120 feet from my tower, which I use with my 
second radio. I don't get S7 noise levels, but I sometimes feel as if 
it is more of a dummy load....


Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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