Hi Dave, Joe,
According to the fine print, the formula is for antennas more than about 10 elements, and boom lengths 2 wl and longer. Dave's 3 element 2m beam doesn't quite qualify. Joe, you're probably ok, but still...
I'd put them as far apart as is practical, and not worry so much about the math. How long is your cross arm? 6 or 8 feet? Start there. These are relatively blunt instruments; don't over-think it. :)
To Joe's numbers, two of the 65's would be placed 65 (what, inches?) apart, or about 5'. By the ideal different bands diagram, the mixed pair would be half of 65 plus half of 123, or 94 apart, or about 8'. But the different bands practical diagram says, basically, anything farther than half of whichever is the higher band's distance, so if that's the 123 antenna, about 5'. So, like I said, 6-8 feet is probably fine.
Greg KO6TH
Joe wrote:
Now when using that formula on that page, And you get an answer of 65 for one antenna and 123 for another,
Now if they were identical antennas IE the 65, I would place the two 65 apart correct?
Now if one is 65 and the other is 123, what should be the optimum spacing?
Joe WB9SBD Sig The Original Rolling Ball Clock Idle Tyme Idle-Tyme.com http://www.idle-tyme.com On 2/21/2017 2:44 PM, Mike Thompson wrote:
I replied to this earlier, but I thought it would be worth sending to the whole board. The idea is to get each antenna out of the aperture of a smaller antenna as much as possible.
Hope this helps.
http://www.ifwtech.co.uk/g3sek/stacking/stacking2.htm
On Tue, Feb 21, 2017 at 1:01 PM, Dave Mann cwo4mann@comcast.net wrote:
Same Question here, RE placing the two 2-M Yagis directly next to each other and 90 degree angles.
I read where I can put both of my Cushcraft 3-element Yagis together, spacing the elements on one so that they are ahead or behind the other set of elements. Then binding the two Yagi booms together. Feed line would be one 1/4 wave and one 1/2 wave, "I think". Then the two feed lines would be soldered together and attached to a PL-259.
I put a couple of photos of my construction project on the AMSAT Facebook page, but it only shows the 70cm Cushcraft Circularly Polarized Yagi at one end of the cross-boom and a single 3-element Cushcraft Yagi at the other end of the cross-member.
I originally placed the second 2-m Yagi at a 1/4 wavelength away from the end Yagis, but saw some pretty high SWR readings on both the 70cm and on both 2-m Yagis.
This is more difficult to explain in writing than to actually do. I will get some photos up to my Ham Radio DropBox account and post the link here, "real soon now". Photos here might be more illustrative than my written explanation (pun intended).
I appreciate all of the comments and other advice received here and on the Facebook AMSAT page.
Esto es para mis amigos de habla hispana:
La misma pregunta aquí, RE colocando los dos Yagis 2-M directamente al lado del otro y ángulos de 90 grados.
Leí donde puedo poner ambos de mis Cushcraft de 3 elementos Yagis juntos, espaciando los elementos en uno para que estén por delante o detrás del otro conjunto de elementos. Luego se unen las dos barras de Yagi. La línea de alimentación sería una onda 1/4 y una onda 1/2, "creo". A continuación, las dos líneas de alimentación se soldarían juntas y se unirían a un PL-259.
Puse un par de fotos de mi proyecto de construcción en la página de Facebook de AMSAT, pero sólo muestra los 70cm Cushcraft circularmente polarizado Yagi en un extremo de la cruz-boom y un solo 3-elemento Cushcraft Yagi en el otro extremo de la cruz- miembro.
En un principio colocé el segundo 2-m Yagi a una longitud de onda 1/4 lejos del extremo Yagis, pero vi algunas lecturas bastante altas de SWR en ambos los 70cm y en ambos 2-m Yagis.
Esto es más difícil de explicar por escrito que hacerlo. Voy a obtener algunas fotos hasta mi Ham Radio DropBox cuenta y publicar el enlace aquí, "muy pronto". Las fotos aquí pueden ser más ilustrativas que mi explicación escrita (juego de palabras).
Agradezco todos los comentarios y otros consejos recibidos aquí y en la página de Facebook AMSAT.
73's
Dave N4CVX
On 02/21/2017 10:23 AM, Joe wrote:
OK using this image as a reference,
http://i67.tinypic.com/28mpzkh.jpg
Ok the yagis are 8 elements on 2 meters and 21 elements on 70 cm. Similar boom lengths.
Now when vertically polarized and stacked side by side as in the top picture how close can they get to each other before starting to mess with each other.
Same thing in next image but horizontally polarized so above and below each other.
Now if they are 90 deg in rotation IE: one is vertically polarized and the other horizontal, I'm thinking they could even be on the same boom correct?
So that brings in the third drawing same antennas but at 45 deg to the horizon but 90 to each other, How close can they get without bugging the other?
Now with the 45 deg angle thing, how much will a metal cross boom mess with them?
Joe WB9SBD
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Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb