Topband: Thanks!

[ZR]

Are you now claiming that the thousands of bead choke baluns in use for 
decades at HF and 6M dont work?

I suspect that those who have been happy with the results in mimizing 
feedline radiation would heartily disagree....

Carl
KM1H


----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <topband at contesting.com>
Sent: Tuesday, May 21, 2013 11:58 AM
Subject: Re: Topband: Thanks!


> On 5/18/2013 10:35 AM, Charlie Cunningham wrote:
>>   If you get the larger beads/tubes thatwill fit over RG-213 etc. you can 
>> make excellent 1:1 current baluns by slipping them over the cable before 
>> putting the connector on.
>
> These are not "excellent" 1:1 current baluns below about 75 MHz. Below 
> that range, they are a lousy common mode choke, because they are 
> inductive. Inductive chokes resonate with a line that is capacitive, so 
> they actually increase the current. A line shorter than a quarter wave is 
> capacitive; so is a line between a half wave and 3/4 wave. And so on. 
> That's why we want a choke that is highly resistive -- the resistive 
> component always reduces common mode current, which is the objective of a 
> common mode choke (the so-called "current balun.")
>
> There's an extensive discussion of this in my RFI tutorial, and also in 
> the Coax Chokes power point (which is a pdf).  On my website. 
> k9yc.com/publish.htm
>
> 73, Jim K9YC
>
>
>
> All good topband ops know how to put up a beverage at night.
> _________________
> Topband Reflector
>
>
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