[Lowfer] Need education on Isolation transformers

[Paul Daulton]

You have two choices:
1 build a transformer for 1:1 and put a tuner in front of it to 
transform high impedance of antenna to 50ohms , if the transformer is 
in front of the ant tuner one would have to have a very high reactance 
of each winding. better to transform down to 50 ohms then isolate. as a 
rule the reactane of a transformer should be 10 to 20 times the 
reactance of the line. At 50ohms the reactane of the windings of the 
isolation transformer should be 800 to 1000 ohms with 1:1 turns ratio. 

2 build a FET amp with high impedance gate input and 50 ohm source 
follower to the isolation transformer. That amp would have to be 
battery powered for correct isolation I read some where that a FET is a 
transformer that amplifies somewhat. 

An "L" tuner feeding a 1:1 isolation transformer would be the easiest 
approach. 

Have I confused you more?
Paul

Quoting Andy - KU4XR <ku4xr at yahoo.com>:
> Ok Gentlemen;
>
> I will appreciate any and all information. I have  a 160 meter
> Windom with the ends going east and west. Connected to the windom
> is an 80 meter dipole with the ends going north and south. The
> APEX is 32 feet AGL, Feedline is RG59U, 25 feet wound on a 3 inch
> PVC pipe at the feedpoint, and 25 feet wound on 3 inch PVC pipe at
> the shack entrance, total feedline length is 100 feet. 
>
> I have searched the internet to a dead end; How do I determine the
> Impedance of this antenna setup for 500 KHz, 180 KHz, 137 KHz, for
> receive purposes. I can't construct an isolation transformer for the
> feedline without knowing the windings ratio. The only thing that I
> have found out is that a short dipole will present a high Impedance
> and the shorter it is in wavelength, the higher the Impedance. 
>
> This is another step in my learning process, I appreciate your
> patience greatly. 
>
> 73 :::
>
>
>
> Andy - KU4XR - EM75xr - Friendsville, TN. 
> LOWfer Beacon " XR " @ 185.29866 KHz ( QRSS-60 )
> Coordinates:  N:  35* 43' 54" - W:  84* 3' 16"
> http://www.myspace.com/beaconxr
> http://webpages.charter.net/ku4xr/
>
>
>
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Paul Daulton K5WMS
beacon WMS 185.3005 khz qrss30/slow 24/7
Jacksonville,Ar 72076
em34wu