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Author Topic: Effect of bad choke winding?  (Read 333 times)
MSPJ
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Posts: 64




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« on: November 10, 2007, 11:25:55 PM »

Hi - I just added a choke coil to the coax coming off my G5RV stub.I didn't wind it on a form - I just coiled it free form to the approximate size, keeping the coils as close to the same size as I could manage - and then taped the coils together.  

First - will this make the coil totally ineffective?
Second - can it hurt in any way - signal attenuation, susceptibility to nose?

Thanks,
Michael
KB1PIE
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N3OX
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Posts: 8847


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« Reply #1 on: November 10, 2007, 11:45:18 PM »

It won't make the coil totally ineffective but it might make it less effective.

It absolutely will not attenuate the signal.  It's just some coax, doesn't matter how you coil it.  The signal picked up by the antenna that makes its way to the radio is ONLY ON THE INSIDE .

It is *possible* that the coil could make the antenna *more* susceptible to noise but it's very unlikely.

The way it could happen is described in here:

http://www.audiosystemsgroup.com/RFI-Ham.pdf

Search for "threshold impedance"

It is possible to add a choke to a feedline and accidentally resonate some undesired path from antenna to ground but I doubt you did that.

The file above is a good read.  It's pretty technical but it will help you a lot in your attic antenna situation if you keep it handy.


Dan




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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WA3SKN
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Posts: 5499




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« Reply #2 on: November 13, 2007, 05:21:03 AM »

You might want to use some cable ties on that, the tape will not hold too long.
The coil will not hurt anything, and might help.

-Mike.
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K8AG
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Posts: 352




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« Reply #3 on: November 13, 2007, 10:48:35 AM »

SKN is right.  Tape will not last at all.

I have been running several turns of coax taped tywrapped together for several years with not problems.  Be sure to use UV resistant (black) ties.

73, JP, K8AG
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