Topband: 2 Wire Beverage Feedpoint Matching

[i4jmy at iol.it]

It’s a good advice if RF transformers for this application are wound as multifilar windings, interleaving wires, each winding covering all the available core space, side to side with the others. 
If for example the primary is 8 turns and the secondary 32 turns, there will be 5 windings on the transformer. In practice, the primary is one of the 8 turns windings, while the 32 turns of the secondary are composed by the sum of the other 4 windings, consisting each one of 8 turns (end of one section has to be connected with the beginning of the following). 
Turns number are function of desired frequency (band), core permeability and size.  
Note that turn ratio is a parameter relative to voltage (or currents), the transformer impedance will be transformed accordingly with this, but into another factor. 
In case an impedance step up of 2.6 is needed, the required turn ratio is 1.6, not 2.6.
Looking at your application, T1 could be a four wires, one winding for primary and three windings (actually 2.6) for secondary. If primary is 8 turns secondary is three 8 turn windings, the third one tapped at the 5th turn
T4 could be 1:1.6 ratio transformer double secondary, one winding primary, one and a half secondary (actually 1.6). If primary is 8 turns, secondary is two 8 turns windings, the second tapped at the 5th turn. Watch out the secondary output must be out of phase.
The above transformers for beverage applications are not critical, slight changes in turn ratios to avoid fractions of turns are perfectly acceptable.

73,
Mauri I4JMY


> I have never wound a transformer before and could use some help. I am trying
> to build a matching network for a 2 wire beverage. Antenna is 8ft high made of
> #14 wire. Wires are spaced 12" apart and its 585 ft long. At the far end I am not
> using a reflection transformer...trying to keep things simple...so one wire is open
> and the other grounded. The feedline is 75 ohms. The cores on hand are FT82-75.
> So if I use the data from "Low Band Dxing" I come up with the following:
> 
> T4 - Center tapped transformer: primary = 8t secondary = 29t
> T1 - other transformer:             primary = 8t secondary = 21t
> 
> I came up with this by using table 7-12 in the book which suggests a turns ratio
> for T4 of 3.8 and T1 of 2.6.
> 
> I have looked at other information on the internet and also in Misek's book and see
> other information that seems to be different than the above. Can anyone tell me if
> the data above seems ok or am I out in left field??
> 
> Thanks,
> Harry
> W0PI