Richard,
I agree it's good to put the relays at the base of the tower for easy access.
I first learned about using different length feedlines in stacks from Dallas
Carter, W3PP (SK). He wrote an article explaining it for the January 2000 CQ
Contest Magazine, and an excerpt is here:
http://www.qsl.net/w3pp/Pro1.htm
73/Jon
Jon P. Zaimes, AA1K
Tower climber for hire
http://www.aa1k.us/
Cell: 302-632-2353
Reviews of AA1K tower work on eham website:
http://www.eham.net/reviews/detail/12922
Hug your favorite tower every day, and always stay connected to it.
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Richard Smith
Sent: Thursday, May 3, 2018 9:09 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis
Thanks for the feedback. There is a lot of great experience on this reflector.
Wayne,
What is the benefit of making the feedlines odd multiples of a quarter
wavelength long? I have heard this elsewhere, but have not yet figured out the
benefit. Does it depend on the type of phase box - whether it is a simple relay
switching box or a Stackmatch-type box with broadband transformers?
73, Rich, N6KT
From: Wayne Kline <w3ea@hotmail.com>
To: "john@kk9a.com" <john@kk9a.com>; "towertalk@contesting.com"
<towertalk@contesting.com>
Sent: Thursday, May 3, 2018 5:18 PM
Subject: Re: [TowerTalk] Coax Lengths for Stacked Yagis
Rich,
I to am a supporter of having the phase box at the base of a tower. I am also
subscribe to the notion of feed lines especially after a switch box/phase box
be ODD multiples of ¼ wave
Obviously taking the volicity factor into account. There has been more then
one occasion where a phase box got hot switched and had to be changed out in
the DARK.
Wayne W3EA
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
________________________________
From: TowerTalk <towertalk-bounces@contesting.com> on behalf of john@kk9a.com
<john@kk9a.com>
Sent: Thursday, May 3, 2018 8:04:08 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Coax Lengths for Stacked Yagis
I missed seeing your Bonaire tower construction project in March but I heard
that you made positive construction progress with one tower. It's definitely
not easy building a station away from home.
It is a wise choice to put the antenna relays at the base of the tower. It is
really convenient when trouble shooting and relays are probably the most
problematic electrical part of the antenna system.
My phasing relays are also at the tower bases. I run equal lengths of Heliax up
the tower and coil the excess. Shortening one coax 1/2 wl will give you a very
high radiation angle. Shortening a coax by one wavelength seems like it will
give you the correct radiation pattern but is the one antenna a cycle off?
Equal length feedlines is so easy.
John KK9A (PJ4R in 2018 WPX Phone)
Richard Smith n6kt wrote:
I am part of a team that is building a station that will incorporate stacked
yagis on 20 thru 10 meters. We plan to put all of the RF switching at the base
of the towers, for ease of troubleshooting and maintenance. My question deals
with the lengths of the coax runs between the yagis and the switching box at
the base of each tower.
Example - 15 meter stack:
Upper Yagi at 150'Middle Yagi at 120'Lower Yagi at 90'
One option is to run equal lengths of coax from each yagi down to the switch
box, and coil up the excess coax from the middle and lower yagis. But does it
make more sense to use shorter runs of coax from the lower antennas to the
switchbox? Specifically, if the coax runs from the lower yagis are shorter by
multiples of one-half wavelength compared to the upper yagi (using the velocity
factor of the coax in the calculation), would all of the yagis still be in
phase?
Thanks in advance,
73, Rich, N6KT
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