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qrp balun

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William Schmidt

qrp balun

Ed,

I built http://file:///Users/william/Downloads/Balun%20Manual%20-%20final-2.pdf and it works just fine. It comes from the NJQRP webpage. I've used it at 5 watts but the author says that he ran it up to 100 watts without heating.

Bill, WV1N

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Randy Moore

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

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.

Tnx es 73,
Randy, KS4L

On Nov 5, 2012, at 12:43 PM, William Schmidt <[hidden email]> wrote:

>
> Ed,
>
> I built http://file:///Users/william/Downloads/Balun%20Manual%20-%20final-2.pdf and it works just fine. It comes from the NJQRP webpage. I've used it at 5 watts but the author says that he ran it up to 100 watts without heating.
>
> Bill, WV1N
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

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Don Wilhelm-4

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

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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Jim AB3CV

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

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 <[hidden email]> 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.
> >
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

Randy Moore

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

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 <[hidden email]> 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 <[hidden email]> 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.
>> >
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>