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Re: [TowerTalk] homebrew 1:1 current balun

To: towertalk@contesting.com
Subject: Re: [TowerTalk] homebrew 1:1 current balun
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 4 Dec 2015 10:13:05 -0800
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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

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