[Premium-Rx] Re: Premium-Rx digest, Vol 1 #41 - 1 msg The 'Ideal' Logwire ([email protected])

Tue Jan 7 07:01:01 EST 2003

Hi All,
I use a 250 foot dipole fed with open wire line, #10 spaced 4 inches with
old Johnson spreaders. My antenna tuner is a 50 ohm to 200 ohm broad band
transformer. The 200 ohm
side is center tapped to ground. The two ends connect to two L networks that
mechanically track each other. The inductors are 22 UH variable and the caps
are a pair of 300 pF Cardwell bread slicers with 10 KV spacing. This
configuration works very 
well down to about 1.8 mHz. My QRO is a 4CX3000A with a pair of UTC CG310
plate 
transformers. (I used 6 2 inch cores and #14 wire) Sevick's book is good.
fc 

-----Original Message-----
From: AKnott at WTD71.de [mailto:AKnott at WTD71.de]
Sent: Tuesday, January 07, 2003 9:41 AM
To: premium-rx at ml.skirrow.org
Subject: [Premium-Rx] Re: Premium-Rx digest, Vol 1 #41 - 1 msg The
'Ideal' Logwire (NewRadioChap at aol.com)

I got some experience with broadband transmission line BalUns and UnUns,
even QRO-versions. Take a look at those two famous book Jerry Sevick W2FMI
wrote: "Transmission Line Transformers" and "Building and Using BalUns and
UnUns". I think that one will be able to build a transformer of 50:200Ohm or
even 50:450 Ohm for 10Khz to 10MHz with stacked 1:1 transmission line BalUns
of 100-Ohm-line or 150-Ohm-line wound around different selected ferrite
materials in each "leg" to keep the decoupling stable. The effort would be
relatively high: for example 18 different coils on ferrite (three times a
leg of four differnt toroids and pot cores). This kind of transformer would
just be able to serve for reception because the ferrites would have to have
more volume for transmission purposes and therefore the line would become
too long for the upper edge (10MHz)! A network analyzer with the capability
to measure S-parameter or just forward transmission would help very much.
Anyway, even such a transformer will NOT be able to match a wire at all
frequencies between 10kHz and 10MHz! DD3LY

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