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#1
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Rule of Thumb for coax chokes
Based on some calculations I did today, I am offering
an original rule of thumb (as far as I know). Regarding a coax choke, when deciding how many turns of coax to put on a 2 liter pop bottle at two turns per inch, one needs to avoid the self-resonant frequency. So don't put more turns on the choke than the number of meters in a wavelength, e.g. no more than 20 turns on 20m, no more than 6 turns on 6m. Backup calculations will be published on my web page. -- 73, Cecil http://www.qsl.net/w5dxp |
#2
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Rule of Thumb for coax chokes
Why avoid the self-resonant frequency?
That's the frequency at which the choking impedance is a maximum. ---- Reg |
#3
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Rule of Thumb for coax chokes
Cec,
Suppose you havn't got a pop bottle but only a length of plastic drain pipe of different diameter. You will need a different rule of thumb for every contingency. ---- Reg. |
#4
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Rule of Thumb for coax chokes
Reg Edwards wrote:
Suppose you havn't got a pop bottle but only a length of plastic drain pipe of different diameter. Then I use my EXCEL spreadsheet which allows variation in the number of turns per inch and diameter of the coil. If you would like a copy, it can be downloaded from http://www.qsl.net/w5dxp/Corum1.xls You will need a different rule of thumb for every contingency. 2 liter pop bottles are in abundance in the US. If a coil form is used for a coax choke, that's the most likely. -- 73, Cecil http://www.qsl.net/w5dxp |
#5
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Rule of Thumb for coax chokes
Cecil Moore wrote:
Reg Edwards wrote: Suppose you havn't got a pop bottle but only a length of plastic drain pipe of different diameter. Then I use my EXCEL spreadsheet which allows variation in the number of turns per inch and diameter of the coil. If you would like a copy, it can be downloaded from http://www.qsl.net/w5dxp/Corum1.xls You will need a different rule of thumb for every contingency. 2 liter pop bottles are in abundance in the US. If a coil form is used for a coax choke, that's the most likely. But then you have to drink 2 liters of wet, sticky, gooey, sickeningly sweet, soda pop. 73, Tom Donaly, KA6RUH |
#6
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Rule of Thumb for coax chokes
I like to drink soda water from 2l bottles with a splash of lemon
juice; sounding pretty good right now given that it's 97F in Maryland and the weather this week is, as per the NWS, "Excessive Heat" Dan But then you have to drink 2 liters of wet, sticky, gooey, sickeningly sweet, soda pop. 73, Tom Donaly, KA6RUH |
#7
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Rule of Thumb for coax chokes
Tom Donaly wrote:
2 liter pop bottles are in abundance in the US. If a coil form is used for a coax choke, that's the most likely. But then you have to drink 2 liters of wet, sticky, gooey, sickeningly sweet, soda pop. Lipton and Nestea tea also come in those bottles as does lots of sugar free diet stuff. -- 73, Cecil http://www.qsl.net/w5dxp |
#8
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Rule of Thumb for coax chokes
On Wed, 02 Aug 2006 21:17:04 GMT, "Tom Donaly"
wrote: But then you have to drink 2 liters of wet, sticky, gooey, sickeningly sweet, soda pop. 73, Tom Donaly, KA6RUH Or look in the nearest garbage can or dumpster. Of course, there are two liter bottles of water as well. -- 73 for now Buck N4PGW |
#9
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Rule of Thumb for coax chokes
Tom Donaly wrote:
Cecil Moore wrote: Reg Edwards wrote: 2 liter pop bottles are in abundance in the US. If a coil form is used for a coax choke, that's the most likely. But then you have to drink 2 liters of wet, sticky, gooey, sickeningly sweet, soda pop. 73, Tom Donaly, KA6RUH We get 'sparkling water' in 2l bottles because we like the fizzy feel to our beverages. They also have club soda and soda water in 2l bottles. Keep cool, Galen, W8LNA |
#10
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Rule of Thumb for coax chokes
Reg Edwards wrote:
Why avoid the self-resonant frequency? That's the frequency at which the choking impedance is a maximum. Personal preference - I would rather the choking impedance be at maximum reactance rather than at maximum resistance. I think that saves a little bit of power. -- 73, Cecil http://www.qsl.net/w5dxp |
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