AW: [TowerTalk] Stacking of Quads

[Gerhard Burian]

Dear Pete,

What i did so far was quite simple. I took the original dimensions from the
4 ele 5 band Quad from Lightningbolt (24 ft boom) and run a free space
simulation. The data for 20m are:

f(Mc)    gain (dBi)    bwidth/az(°) bwidth/el(°)   F/B(dB)
14.0      8.2            60            68            6.0
14.2      9.0            62            70            17.4
14.4      8.6            60            68            9.6
Bandwidth for SWR>2 is about 200kc

I took the two directors off and made a 2 element Quad on a 12 ft boom out
of it and got without any further optimization:

f(Mc)    gain (dBi)    bwidth/az(°) bwidth/el(°)   F/B(dB)
14.0      6.9            68            82            3.8
14.2      7.4            74            90            10.8
14.4      6.5            78            98            8.0
Bandwidth for SWR>2 is again about 200kc

Than I made a stack of two of those with center distance of 24 ft and I got
without any further optimization:
f(Mc)    gain (dBi)    bwidth/az(°) bwidth/el(°)   F/B(dB)
14.0      8.6            70            58            5.5
14.2      9.1            74            60            14.9
14.4      8.6            76            62            14.6
Bandwidth for SWR>2 for this was about 400kc !!!

On 10 and 12 m I am placing a third element as driven element between the
two others. Because of the 3 ele and the higher stacking distance in
relation to wavelenght the stacked array will have 11.5 dBi of free space
gain.

I am now asking for any information if it is worth that I do further
optimizing of the stacked array. It seems to be easier to adjust and mount
two 2/3 ele 5 band Quads instead of one 4/5 ele Quad. Switching of
lower/upper/both would be an advantage. It seems that the bandwidth for
SWR>2 is larger.
BUT: Can two quads be really built with the same feed impedance that
matching of two of them could be done without measurement of phase angles?

73's
Gerhard OE3GBB


-----Ursprüngliche Nachricht-----
Von: Pete Smith [mailto:n4zr@contesting.com]
Gesendet: Friday, August 04, 2000 11:42 PM
An: Gerhard Burian
Betreff: Re: [TowerTalk] Stacking of Quads


At 10:40 PM 8/4/00 +0200, you wrote:
>
>After some days of simulating 4 ele 5 band Quads it came into my mind to
try
>a stacked array of two 2 ele 5 band Quads with vertical center distance of
>24 ft (what could fit to my tower).
>First results are encouraging as the influence between the bands are
>minimized and a longer boom could be used easily. The array seems to have
>better bandwidth but slightly lower f/b. Of course 24 ft stacking for 20m
is
>to small, but a compromise.
>Is there any experience out there or any comments?

It sounds like you are finding something similar to stacking short-boom
2-element yagis.  I presume you mean "beamwidth" above rather than
bandwidth.  A compromise stack of 2-element yagis yields about 2 dB
additional forward gain (over a single antenna in the top position) on 20m.
 What is the comparable figure for your quad stack?

73, Pete Smith N4ZR

The World Contest Station Database
is back up and running at
http://www.qsl.net/n4zr




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