[TowerTalk] Re: Amidon FB-43-1020 beads.

[Bill Coleman AA4LR]

On 10/19/97 1:46, george fremin iii at geoiii@bga.com wrote:

>>Can you use too many?  Why?
>
>The only limit to the number is financial.  But the
>ones further from the load work less and less
>until the ones 7 or 8 removed from the load
>are really doing nothing. 

You know, was musing about this problem just the other day. (I have too 
long a commute....)

It seems unfair that the first bead or two in a bead balun are doing all 
the "work." It also produces a failure point for the balun -- since that 
first bead is taking all the brunt of the currents that we are trying to 
eliminate.

So, the thought problem is -- how can we create a bead balun, where each 
bead contributes equally and disappates the same amount of current?

Impossible? Nope. Read on.

>>What is the diffrence in using 43 or 77 or ??
>
>On paper 77 material looks better for HF.  It has
>more mu and looks like it will require fewer beads,
>but this is what the DX Engineering balun used
>(until I convinced them to change to 43) and what
>melted my coax.  The 43s  will require a few more 
>beads but it will not smoke your coax.

Now, if we could just get Amidon to produce them, why not have beads of 
gradually increasing permability (mu)? If we increase the permability in 
a logorithmic fashion, each bead will be disappating the same about of 
energy. Of course, this will require more beads....

Of course, the answer may simply be to use a couple of 43s first, then 
follow up with 77s. If the first 43 doesn't burn throught the coax, it 
isn't likely the 77s will, either.

>>Also, I was curious as to the use of the #43 core instead of the #77 core.
>The 
>>#77 has better specs in the less than 30mhz range, however I am not sure if
>>it is
>>enough better to make appreciable difference. You might comment on this. 
>>
>HEAT (as I mentioned in the Geo part of the note) is the only reason.  If you
>are a exciter only type of guy then the 77s will work even better than the
>43s.  But if you like to warm the ionosphere(but not your coax) you had
>better use the 43s.

Perhaps mixing and matching them is the best idea yet.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901


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