[VHFcontesting] stacked yagi's

Mon Apr 12 21:00:34 PDT 2010

Hi Dave,

First, in my message below, I mis-stated about multiple half-wavelengths. I meant to say multiple quarter-wavelengths. But, to answer your question:

Yes, use two equal lengths of 50 ohm coax. Make sure the yagis are both mounted the same way.

73,
Paul, K7CW

________________________________
From: david vari <david_vari at yahoo.com>
To: Paul Kiesel <k7cw at yahoo.com>
Cc: vhfcontesting at contesting.com
Sent: Mon, April 12, 2010 4:08:33 PM
Subject: Re: [VHFcontesting] stacked yagi's

all replies have been interesting to read. but in my case i can not stack one on top of the other my one 13b2 is just above the houses in my area and need to go side by  side. will i still need 2 equal lenghts of coax with my pd-2 power divider?

dave-n2rhl

--- On Sun, 4/11/10, Paul Kiesel <k7cw at yahoo.com> wrote:

>From: Paul Kiesel <k7cw at yahoo.com>
>Subject: Re: [VHFcontesting] stacked yagi's
>To: vhfcontesting at contesting.com
>Date: Sunday, April 11, 2010, 1:56 PM
>
>
>If you use a power divider, use two equal lengths (it doesn't matter how long they are) of 50 ohm coax, from the power divider ports to each yagi. The impedance transformation is going on in the power divider, so  you already have 50 ohms available at each of the power divider's ports.
>
>If you elect to use coax, use 75 ohm coax so you get the proper impedance transformation. You must use exact multiples of an electrical half wavelength. You will want to use as little coax as possible to reduce your losses in the coax, so if you elect to make both lengths of coax an EVEN number of half wavelengths long, then you will orient the feeds of the antennas so that they are both on the same side, symmetrical with each other, if you will. But, if you decide to have one length of coax be an EVEN number of half wavelengths long and the other length of coax an ODD number of half wavelengths long, then you will need to reverse the feed
> on the second yagi so that it is reverse from the first yagi. This is because the extra half wavelength of coax that you have going to one of the yagis will result in a 180 degree shift in phase. So, in order to get both antennas in phase with each other, you will need to reverse the feed on one of them by flipping the
>antenna upside-down or by mechanically re-arranging the feed.
>
>73, 
>Paul, K7CW
>
>
>
>
>________________________________
>From: Jon Casamajor <k6el at comcast.net>
>To: vhfcontesting at contesting.com
>Sent: Sat, April 10, 2010 2:09:05 PM
>Subject: Re: [VHFcontesting] stacked yagi's
>
>Hi Paul,
>
>I am a little confused on what you are doing I
> guess.   I have two M²
>420-50-11 Yagis stacked vertically, that is one above the other.  I am using
>a standard M² splitter and stacking harness and the distance between the
>Yagis is 28” and the phasing lines are identical in length however I’m not
>entirely sure of their length as they are living at about 100’ now.  J
>
>You said… “(note that I might switch units without warning)”, so I may not
>be seeing something here.  If both phasing lines are the same length
>wouldn’t they be fed in phase?  My little stack is on my QRZ page in case
>I’ve confused you in return.  The little stack works quite well but I’m
>planning to replace it soon with a 4329WL as the stack is a little sharp and
>I need a bit more ERP.
>
>
>
>
>
>73, Jon
>
>K6EL
>
>-----Original Message-----
>
>
>
>
>
>------------------------------
>
>
>
>Message:
> 2
>
>Date: Sat, 10 Apr 2010 03:07:25 +0000 (UTC)
>
>From: Paul Decker <kg7hf at comcast.net>
>
>Subject: [VHFcontesting] stacked yagi's
>
>To: vhfcontesting at contesting.com
>
>Message-ID:
>
>
><1210296233.8429611270868845217.JavaMail.root at sz0009a.westchester.pa.mail.co
>mcast.net>
>
>          
>
>Content-Type: text/plain; charset=utf-8
>
>
>
>
>
>
>
>Hey group, 
>
>
>
>
>
>
>
>I'm in the
> process of stacking two 11 element 70cm yagi's.? I've modeled it
>in eznec and I think the optimum distance is about 42".? (note that I might
>switch units without warning). 
>
>
>
>
>
>
>
>Once I have the two 50 yagi's stacked, my model says I need to have one 180
>out of phase, does this seem right? 
>
>
>
>
>
>
>
>If that is the case, then I need different lengths of coax to feed each
>antenna. 
>
>
>
>
>
>
>
>Should I use a 50 ohm power divider and feed each antenna with 1.25w and
>1.75w 50 coax, or should I feed with 1.25 and 1.75 75 Ohm coax and simply
>use a T connecter.? Is there an advantage of one over the other? 
>
>
>
>
>
>
>
>thanks for any help, 73, 
>
>
>
>Paul (KG7HF) 
>
>
>
>
>
>------------------------------
>
>
>
>_______________________________________________
>
>VHFcontesting mailing list
>
>VHFcontesting at contesting.com
>
>http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
>
>
>
>
>End of VHFcontesting Digest, Vol 88, Issue 9
>
>********************************************
>
>_______________________________________________
>VHFcontesting mailing list
>VHFcontesting at contesting.com
>http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
>
>
>      
>_______________________________________________
>VHFcontesting mailing list
>VHFcontesting at contesting.com
>http://lists.contesting.com/mailman/listinfo/vhfcontesting
> 