TopBand: Beverage Ant

[w8ji.tom]

Hi Jeff,

> Hi all - I put up a two wire Beverage antenna this weekend and need to
> build the matching transformers. Does anyone know a local (Boston Area)
> source for
> Indiana General MN-8-CX toroid cores? I only need two so I'd like to find
a
> local source. Thanks.
> Please reply to parker@ll.mit.edu
> Jeff, KA1GJ

The Indiana General MN-8 CX core is a good core for 20-200 kHz, but the
wrong mix for amateur bands.

The problem someone "missed" in selecting that core, is that core
permeability varies with frequency. That core,  despite having very high
ui, actually has much less operating permeability on 160 meters than lower
initial ui cores when used on 160 meters and up. The MN-8 CX is one step
above a nail wound with wire, even the core manufacturer doesn't recommend
it for this application.

A core with the highest operating frequency permeability insures the
transformer will use less turns and have the best performance.

I'd use a more common 73 or 61 mix core. Not only are they easier to find
(mail order sources like Amidon),  they also work better. 
    
73 Tom

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