[TowerTalk] homebrew 1:1 current balun

[Jim Brown]

On Thu,12/3/2015 9:59 AM, Kelly Taylor wrote:
> Their prices are about $1 better than KF7P on the Mix 31 2.4” OD cores, and $2 worse than KF7P on the Mix 31 Biggest Clamp-ons ($16.95 at pro audio vs. 14.95 at KF7P).

While it's great that guys like Howard are distributing #31 cores in 
small quantity, a far better approach is to organize a group purchase. 
I've done several, and been a part of several organized by others. Some 
givens. #31 is the material we want for HF, and I've zeroed in on three 
parts as most useful.  They are the 2.4-in o.d. toroids (often called 
FT240 by those who sell them at huge markups), what I call the "biggest 
clamp-on", which is 1-in i.d., and a medium clamp-on that is 0.75-in 
i.d. The first two parts are most useful on antennas; the smaller part 
is ideal for choking victim equipment (hi-fi gear, computers, etc.) and 
noise sources.

If you can group the purchase of active hams in several local clubs (I'm 
thinking contest and DX clubs here), you can buy from distributors at 
prices that are half the cost of the lowest cost retailers. In a group 
purchase, I've never paid more than $5 for 2.4-in o.d. cores; shipping 
and tax adds 10-12%. In 2013, I paid $9.08 ($10.25 w/tax and shipping) 
for the "biggest clamp-ons" and $2.28 ($2.65 with tax and shipping) for 
the 3/4-in i.d. clamp-ons. The best vendors I've found are Dexter 
Magnetics (near Chicago) and Lodestone Pacific (Anaheim). I bought 770 
of the smaller 3/4-in clamp, 160 of the 1-in i.d. clamp, and only about 
100 of the "FT240" cores (I had recently done a much larger purchase of 
them).

An important rule for group purchases is to NEVER re-ship cores, because 
they are fragile. Distribute the cores at club meetings, letting members 
pass along deliveries to the guys who live a bit further away and can't 
make meetings. The recommended vendors will take your charge card and 
bill when they ship; this gives you time to pass out the cores and 
collect the most of the money in time to pay your credit card.

These vendors WILL drop ship to multiple locations, so it's easy to 
combine a group purchase with clubs that are geographically separated. 
The first group purchase I organized in 2005 (with the help of K9OR) 
included clubs around Chicago, where I lived then, Milwaukee, and 
Indianapolis. To minimize breakage, ship only in full box quantities. 
Ferrites are fragile. I've never seen breakage in full boxes.

73,Jim K9YC