Topband: Amidon Beads

[Tom Rauch]

> When I contacted Amidon to order some of the new cores I
found that the FB77-6301 only has a single hole and is not
binocular.  They also said the don't make a binocular
version made with type 77 material.

Terry,

Amidon is a retailer or distributor. They don't "make"
anything.

The binocular core is made by FairRite Products and is the
same one I use in HF low or medium power RF transformers. It
normally comes in two mixes, 43 or 73 although FairRite
manufacturers them in custom materials.

You would not want a 77 material, so I assume that was a
typo. 73 material is about optimum in an application like
this since it has an impedance peak at or near 160 meters.
Have an impedance peak near the low frequency end of
response minimizes the number of turns needed.

Check out:

http://www.w8ji.com/core_selection.htm

http://www.w8ji.com/k9ay_flag_pennant_ewe.htm shows a
transformer made from a stack of three cores. You don't
really need the little extra "tail" on the primary. I used
it to improve  balance, but the "K9AY" form of small
terminated loop is not a floating antenna with high common
mode Z, capacitance balance in the windings are not  a
critical parameter.

73 Tom