[Elecraft] [OT] Re: qrp balun - how about not QRP?

[Randy Moore]

Thanks, guys. I've read K9YC's paper before, but needed to be reminded of it!

73,
KS4L

On Nov 5, 2012, at 1:46 PM, Jim Miller <jim at jtmiller.com> wrote:

> Read all but if lazy just go to cookbook near end: http://audiosystemsgroup.com/RFI-Ham.pdf 
>  
> For some useful more detail analysis: http://fermi.la.asu.edu/w9cf/articles/balun.pdf
> Forget you ever heard of the term "balun"
>  
> jim ab3cv
> On Mon, Nov 5, 2012 at 2:37 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>> Randy,
>> 
>> That "balun" will not be very effective below 6 meters.  The inductance
>> of each winding is about 1000 nHy, which provides only 60 ohm choking
>> impedance at 10 MHz.  Sorry, but there are designs out there on the web
>> that do not hold up to scrutiny.
>> An effective balun must have a choking impedance of at least 5 times the
>> feedpoint impedance, so for a 4:1 balun (200 ohms), the impedance must
>> be 1000 ohms or more to be effective.
>> 
>> 73,
>> Don w3FPR
>> 
>> On 11/5/2012 2:16 PM, Randy Moore wrote:
>> > Can I divert slightly?  I want to build this balun
>> > (http://www.combotec.com/projects/balun14/balun14.html)
>> > to use with a 40m delta loop from my K3/100, but the only PVC I have is about 1.25" in diameter, not 40mm (1.5").  How do I compensate for the smaller diameter?  Google searches haven't been productive.
>> >
>> 
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>