[Antennas] mixing balun cores

2002年3月08日 16:49:36 -0500

At 11:29 AM 3/8/2002 -0800, Steve L. wrote:
>Anyone actually build a high power balun using two
>different core materials? I use type-61 for my HF
>baluns usually which is good for 160-10m easily but
>has a much higher mu than the powdered iron cores. I
>was thinking of experimenting with different materials
>in a stack-up... maybe 67/61 or ???
>>I just placed an order for an Alpha 99, upgrading from
>an ancient SB220 and I'll need to re-do my baluns for
>the 1500W output - my old SB220 has "only" 700W out on
>10m (I got QRP WAS/WAC 29 years ago so save the "QRP
>rules" flames, been there, done that).
>>I'm gonna need some super-duper wire, others use the
>center wire and insulation pulled from teflon coax -
>pretty hurky, any other suggestions?
>>73, Steve N4SL Machias, WA CN88xa

You mean using two type materials stacked for one balun? One core will 
take the bulk of the magnetic strain and could saturate while the other one 
does not, and saturation causes non-linearity and higher losses. Cores are 
cheap. I didn't do the math for the type 61 material, but I usually use 
around 100 uhy for a 160 to 10 current balun. Tough to get that frequency 
coverage with a voltage balun. A two core current balun is best. Two 
FT240-xx with a bifilar winding on each should do the job. You will have 
to figure out the xx material. Check Sevick's Ununs and Balun book. CW 
Bytemark (formerly Amidon) will send you a data sheet for the request, or 
you can buy a data book. Check their web site (Do a search). On the wire, 
Sevick uses #14 solid copper enamel insulated which he slips in a teflon 
tube for the high power 4:1 (50 to 200 ohm) ones. You can buy the teflon 
tubing from CW Bytemark and other places. You could also use silver plated, 
stranded teflon insulated wire. I've used it in lower power baluns. Didn't 
do the math, but somewhere around #14 to #16 should be a good match for 
50:200 ohms. You can buy it from RadioShack.com, the commercial division 
of Radio Shack. A bit expensive, but you don't need much. Have you 
considered a 1:1 balun? Easier to build, and will work as well for many of 
the applications. Don't know what you will be using it for.
GL
73, Chas, W1CG