Hi Gang,
Well a successful day so far....I have tried the 2 separate cores and
couldn't get them to balance as Steve mentioned and couldn't get lower than
1.5:1 SWR into the dummy load...tried stacking 2 cores on top of each other,
better, and now 1:1 at 14MHz and up to 1.2 at 30MHz with the enameled #14
bifilar wound...then I tried my MIL spec teflon coated silver plated coax,
which is 12 ga center with .010" PTFE insulation, stripped off the shield
and started with 7 turns bifilar, wrapped every 2" with glass tape then
slowly worked down 1 turn at a time until Shazamm, 4 turns and I have it
flat 1:1 from 1MHz to about 70Mhz with a slight bump around 45MHz up to
1.3:1. At the main freqs of interest 14MHz is 1.00:1, 21MHz is 1.01:1 and
30MHz 1.03:1. Now onto the soak test to see what heat is generated. Then I
am going to try to stack 3 cores and start again...more results later.
I am now actually having fun with this latest success. 2 hours before
baseball starts though so I have a deadline to meet.
73
Paul
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Steve
Hunt
Sent: Tuesday, October 28, 2014 2:13 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Subject: 4:1 balun questions KT-34XA
It's worth noting that the two 1:1 current baluns forming a 4:1 Guanella
balun will likely have very different CM voltages across them, leading to
very different core dissipations. In fact if the two 1:1 baluns are ideal
and the load is balanced, the CM voltage across one will be zero and the CM
voltage across the other will be the input voltage!
The message is that you can't assume that the core dissipation due to CM
voltage and current will be equally "shared" between the two baluns forming
a 4:1 Guanella balun.
Steve G3TXQ
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