Felipe:.
450 Ohm Line is available from sources like "The Wireman" at:
http://www.thewireman.com/antennap.html
I suggest you obtain a 9:1 ratio Current Balun to obtain the 50 ohm match.
DX Engineering has a very good 9:1 Current Balun:
http://www.dxengineering.com/Parts.asp?ID=60&PLID=50&SecID=10&DeptID=40&PartNo=DXE%2DBAL450%2DH10%2DA
I would place this Balun outside of the shack then run coax to the radio.
Download the owners manual on the above Balun from:
http://www.dxengineering.com/pdf/DXE-BAL-Rev2.pdf
Other people have high-power current baluns available, but,
I personally prefer the ones from DX Engineering.
I hope the above answers your impedance transformation question.
Additionally: It would also be very prudent to include a lightening arrestor
on the 450 ohm line before the Balun. A good balanced lightening arrestor
can be obtained from: Industrial Communications Engineers, Ltd.
http://www.iceradioproducts.com/impulse1.html#2
Model 309H is a nice high power version and the model 309 will handle
500 watts.
Good luck,
Wilson Caselli, K1MIJ
----- Original Message -----
From: "Felipe Ceglia - PY1NB" <felipeceglia2@gmail.com>
To: <towertalk@contesting.com>
Sent: Monday, December 08, 2008 8:08 AM
Subject: [TowerTalk] 80m delta loop question
Hello gurus,
After reading the loop section on Low Band DXing, I decided to build a
delta loop for 80m, mostly vertically oriented, and fed 1/4 lambda from
apex. Planning to use ladder line, so I will be able to use it on CW and
SSB portion (PY's are allowed to use only upt to 3.8mhz).
The author suggests using 450ohm ladder line for feeding it, but I could
not find much details about it, so I ask:
Which antenna matching configuration should I use at the end of the
ladder line to transform it to 50ohm?
Could I use other impedance on the ladder line, say 300ohm? Is it critical?
Would I need a given lenght for the ladder line, or could I go random?
73 and thanks,
--
Felipe Ceglia - PY1NB
PR1T team member - Rio DX Group
http://www.dxwatch.com
http://skimmer.dxwatch.com
http://riodxgroup.dxwatch.com
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