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Topband: flag matching transformer ferrite material

To: topband@contesting.com
Subject: Topband: flag matching transformer ferrite material
From: Roger Graves <ve7vv@shaw.ca>
Date: Thu, 19 Feb 2015 18:28:55 -0800
List-post: <topband@contesting.com">mailto:topband@contesting.com>
I have a flag rx antenna that is working well on 160 mtrs. I would like to try 
to use it on 630 mtrs.
The current matching transformer is 3:12 turns on a BN-73-302 core. I assume 
more impedance will be needed for good performance on 630 mtrs. 
I did not find core specs on the FairRite site for frequencies below 1 mHz for 
73 material.
Is 73 material the best choice for a transformer to be used on both 630 and 160 
mtrs?
Would twice as many turns be sufficient for 630 mtrs, i.e. 6:24 turns on one 
BN-73-core, or 3:12 turns on 4 BN-73-302 cores, or 3:12 turns on 2 BN-73-6802 
cores (which have twice the mu)?

Also, is the 73 material still suitable for a broadband transformer up to 30 
mHz? I am using 2:2 bifilar turns on a BN-73-302 core as a 1.8 to 30 mHz 
broadband 1:1 transformer in a receiver. A test shows good swr over this freq 
range, but I do not know if the loss is low at 30 mHz.

Thanks for the help.

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