Re: Tower Optimization de N4KG
First, one must ask do you want versatility or gain.
Versitility is exemplified by several different antennas at
different heights and different directions, providing good
coverage of all directions and waveangles at the flip of a
switch. Multiple tribanders is a good way to achieve this.
If you just want a BIG signal, large stacked monobanders
are the way to go. With lots of antennas, a rotating tower
may be more economical than individual rotors.
For two towers, the 40 / 10 and 20 / 15 combination is a
good approach. 30 ft spacing works well for 5L10's. 35
to 40 ft spacing for 5L15's. 50 ft spacing for 3L20's or 60 ft
for 5 or 6L20's. 80 ft spacing with a pair of 2L40's has as
much gain as a wide spaced 3L40 with the added advantage
of waveangle and directional diversity.
It is tempting to just stack lots of antennas on tall towers.
W6QHS and K6LL among others have found that severe
interactions from closely spaced antennas for different bands
can destroy the added gain of multi element monobanders.
If you can't give your antennas lots of breathing room, you
may be better off with multiple tribanders.
With 2 or more moderately tall towers, suspended 2L 40
Delta Loops are very effective in performance and cost.
Two of them can be placed back to back sharing one reflector.
A 2L Delta loop has as much gain as a short (.25-.30WL)
boom 3L Yagi. I once suspended a 2L40 Delta Loop from
a 20 ft boom on my 130 ft tower. KILLER antenna but it
takes up a lot of space on the tower if you are looking to
stack other antennas.
You will likely never have enough antennas to optimize all
situations on all bands in all directions. Good luck with
your choices!
de Tom N4KG
On Sat, 18 Dec 1999 08:17:03 -0800 Michael Tope <W4EF@pacbell.net>
writes:
>
> Gerald,
>
> What is the bearing of the line between the two
> towers? You might be able to use this a "boom"
> for a wire beam, or for suspending a bobtail
> curtain. KS8S did the latter back in the 80's with
> great success (it was broadside to Europe and
> his ground was very conductive).
>
> I would put a 15/20 stack on one tower, and a 10/40
> stack on the other. You may also want some lower
> antennas on ring rotators since 130/140' will be kinda
> high for high sunspot activity.
>
> For 160 you can shuntfeed one of the towers (they will
> be a little to far apart for a broadside array), or
> use them as supports for a 4 square (this F/B will help
> you on receive if you don't have room for beverages).
>
> Mike, W4EF............
>
> ----------
> From: Gerald Smith[SMTP:w6ter@worldnet.att.net]
> Reply To: w6ter@worldnet.att.net
> Sent: Saturday, December 18, 1999 4:45 AM
> To: towertalk@contesting.com
> Subject: [TowerTalk] Re: Widen the Scope - Optimum Tower
>
>
> Tom took the liberty of adding towers and increasing the size. I
> can't
> change the tower(s) configuration, permit constrains to the listed
> configuration. So let me ask the group, what would you do?
>
> I have 5 acres, flat with no surronding obstacles. I have two towers
> going up, both Rohn 45 at 130 feet. The towers are 390 feet apart.
>
> The only antenna I have bought is a DX Engineering DX40-3. I found
> it
> new in British Columbia. A guy had bought the antenna 3+ years ago
> and
> had never put it up (hardware still in bags). It is a full size
> forty,
> 42 foot boom. Longest element is 74 feet.
>
> I want a single radio contest station.
>
> Gerry, W6TER
>
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