[TowerTalk] BALUN revisited again

[Jim Thomson]

Date: Fri, 8 Apr 2016 16:47:39 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] [Bulk] Re: BALUN revisited again
Message-ID: <5708431B.6030100 at audiosystemsgroup.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

On Fri,4/8/2016 11:36 AM, Bert Almemo wrote:
> As I was reading the post I was wondering if you could use ferrites of
> different mix in the same choke/balun? Would that work or not?

It could work for two chokes in series, as shown in the CMC-230-5K. But 
since the ferrite materials are not specified for this product, it's 
hard to say what they're using. It would make sense to use #31 for the 
lower frequency choke and #43 for the higher frequency choke.

I think the power rating for this choke and the BL2006-3K may be overly 
optimistic. I've fried a similarly constructed choke on a single #31 
core with 1.5kW under heavy contest conditions with an 80M dipole. 
Plugging the equivalent circuit into an NEC model shows the need for at 
least twice the choking Z of a single choke. The second choke doesn't 
need to be at the feedpoint -- it could be well down the line.

73, Jim K9YC

##  say what ?   AFIAIK, he uses  FOUR type 31 cores for the CMC-230-5K ,
2 x cores  for each assy.   8000-11,200 ohms of RS is nothing to sneeze at. Its 
rated at 5 kw pep out.   It wont blow up with 1.5 kw cxr.  Its been tested. 2-30 mhz

##  The BL2006-3k  is a 14-54 mhz balun.  Single core.   5400- 8600 ohms of RS
is again, nothing to sneeze at.   Rated for 3 kw pep out.   It  wont blow up on 20-6m,
with 1.5 kw cxr. 

##  Your  single  core overheated on 80m.   His BL2006-3k  Is rated for 14-54 mhz.
Its not intended to be used on 80m! 

Jim  VE7RF