Topband: Beverage Transformer?

[ZR]

Ive been using BN73-202 cores on 2 wire reversible Beverages in the 500-900' 
range. They work fine down to 150KHz with surprisingly good directivity on 
the LF BC stations as well as NDB's

They are wound as isolated winding transformers with Teflon sleeving to 
minimize interwinding C which has resulted in excellent FB. I would think 
that similar attention to detail would help a single wire unidirectional 
Beverage also.

Turns calculations were done with 500KHz and performance is good thru 30M. 
Even 20 shows directivity which is surprising considering the many 
wavelengths of wire but its lossy, likely not helped by a very poor 250 Ohm 
RF ground resistance on this hilltop rock pile.

Carl
KM1H


----- Original Message ----- 
From: "Tracey Gardner" <tracey.gardner at talktalk.net>
To: <topband at contesting.com>
Sent: Sunday, October 09, 2011 2:43 PM
Subject: Topband: Beverage Transformer?


>
> I would be grateful for some advice on the type of transformer to use on a
> Beverage antenna that I am in the process of erecting.
>
> I have been reading the latest (5th edition) of ON4UN's Low Band DX'ing 
> and,
> on Pages 7-67 and 7-68, he discusses the types of cores to be used and 
> comes
> out strongly in favour of the binocular core type BN 73-202.
> He states that test results for transformers using toroidal cores with 
> type
> 75 and 77 material turned out to be significantly inferior to what was
> obtained with the other two cores.
>
> Now my problem lies in the fact that I want to use the Beverage on 1.8MHz
> and down to 150kHz.
> I'm concerned that a transformer wound using the BN 73-202 core will not
> perform satisfactorily down to 150kHz.
>
> The comments that ON4UN makes about the use of type 75 material have me
> puzzled as there is an excellent, lengthy article by Bill Bowers, the late
> John Bryant and Nick Hall-Patch, VE7DXR which comes out clearly in favour 
> of
> 75 type material for transformers for use between 100kHz and 7MHz.
>
> http://www.dxing.info/equipment/impedance_matching_bryant.doc
>
> I presume that I would have to significantly increase the number of turns 
> on
> the binocular core in order to get it to perform down to 150kHz?
> Is my presumption correct?
>
> Many thanks
>
> Tracey G5VU
>
>
>
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