HI Rick,
Thank you for the reply. Well, perhaps we are onto something here...I am
using what I have in my collection of ferrites, which is a rather large shoe
box full. From what I have been reading, I am basing my selection on the mu
of the material, which 125u seems to be ideal, based on what I read in
Sevick's book. However, as I am obviously still learning about baluns, there
is more to it than I am understanding. Mu is only one of the parameters. I
think since I am running out of time...I should just buy the correct core,
or at least one more suitable. Digikey is my best bet now as I can order
today and it will be here tomorrow. Anything from the US will take a week or
more to get here. Digikey seems to have a good selection from TDK, but
again, I need some guidance on what to look for.
Thanks guys!
Paul
VE7KHz
-----Original Message-----
From: Richard (Rick) Karlquist [mailto:richard@karlquist.com]
Sent: Tuesday, October 28, 2014 10:22 AM
To: Paul; towertalk@contesting.com
Subject: Re: [TowerTalk] 4:1 balun questions KT-34XA
Your choice of MPP is very unorthodox.
MPP = moly permalloy powder.
Generally, ferrite is used for baluns.
It is also used for some tuned circuits but powered iron has some advantages
for tuned circuits and is often used in that application. I've never seen
MPP used for RF. Can you tell us why you chose MPP? How is it different or
similar to "powdered iron"?
73
Rick N6RK
On 10/27/2014 10:37 PM, Paul wrote:
> Hi Guys,
>
> Getting ready to put up my KT-34XA this weekend and just trying to get
> the balun right. I have been experimenting this week with cores and
> windings and have found a combo that sure looks good on the MFJ-259
> and seems to not get too hot on a soak test...what I have come up with
> is a core from Arnolds MPP series which is 125u, 2" diameter and with
> 8 turns 14ga enamel with Fiberglas tape spacers, bifilar wound for
> each half ,on one core, I am flat from 1MHz-45MHz with the MFJ-259.
> Running 500W through it for 5 minutes gets it hot, but I can still
> hold it. I want to end up winding it on 2 cores, half on each and am
> wondering if I should use the same # of turns on each core as I would
> if it were a single core, ie 8 turns on each core, then connect to
> make it a 4:1, or do I need to modify the turns count when I split to
> 2 cores? Also, when splitting to 2 cores, do they need to be oriented
> in any particular way or can I stack them one on top of the other,
> like 2 doughnuts? The antenna is all rebuilt and tested with my single
core balun....just need some + temps and no snow for the weekend.
>
> Your advice is greatly appreciated.
>
> 73
> Paul
> VE7KHz
>
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