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CMCs - MORE (BAD) INFORMATION


David Eckhardt 2021/01/26 20:30

Those wound with the #12 enameled solid conductor do not take power with my
ant/feedline impedances resulting in discharges between bifilar pairs (not
between individual bifilar windings). Also, the green wire of unknown
insulation does not take power. So, those CMCs wound with solid conductor
are coming apart and being rewound in some fashion or another with the
DavisRF "antenna" wire which seems to take power to at least 1.2 kW. Your
mileage may vary with different impedances presented to the chokes.

Those frequencies on which I tried the CMCs at power are:
3.8 MHz 24 - j56
7.15 MHz 493 - j740
Impedances noted are measured at the shack end of the parallel wire
feedline.

Dave - WØLEV

Dragan Milivojevic 2021/01/26 22:02

PTFE tubing is cheap ...

On Tue, 26 Jan 2021 at 21:33, David Eckhardt <davearea51a@gmail.com> wrote:

n2msqrp 2021/01/26 18:04

Dave,



Have you tried teflon covered silver plated wire?



Mike N2MS

> On 01/26/2021 3:30 PM David Eckhardt <davearea51a@gmail.com> wrote:

>

>
>

>
>

> Those wound with the #12 enameled solid conductor do not take power with my
ant/feedline impedances resulting in discharges between bifilar pairs (not
between individual bifilar windings). Also, the green wire of unknown
insulation does not take power. So, those CMCs wound with solid conductor are
coming apart and being rewound in some fashion or another with the DavisRF
"antenna" wire which seems to take power to at least 1.2 kW. Your mileage may
vary with different impedances presented to the chokes.

>

>
>

> Those frequencies on which I tried the CMCs at power are:

>

> 3.8 MHz 24 - j56

>

> 7.15 MHz 493 - j740

>

> Impedances noted are measured at the shack end of the parallel wire
feedline.

>

>
>

>

> Dave

>

>

_._,_._,_

* * *

Siegfried Jackstien 2021/01/27 00:41

i am guessing he does not know how to properly wind a choke ... taking
"no power" let my alarm bell rings

you can in fact use any "speaker wire" and wind that around a donut
shaped ferrite core and have a (more or less) good choke ... so how can
such a bifilar wound choke ... can take "no power" ?!? how did he
connected it??

next is ... a choke (or balun) should be have matched loads ... its not
so well for high reactances ... the "j" value in the example .. is
hifgher as the real part ...

for the parallel feedline ... use a symmetrical tuner and put the balun
on the input end of the tuner ... much better (lower losses in the balun
cause it sees only real and matched part of the impedance)

silver plating and shortwave?? ... rf wise shortwave is not so high that
silver platig makes any difference in the balun

dg9bfc sigi

Am 26.01.2021 um 23:04 schrieb n2msqrp:

Jim Lux 2021/01/26 17:56

On 1/26/21 4:41 PM, Siegfried Jackstien wrote:
>
> i am guessing he does not know how to properly wind a choke ... taking
> "no power" let my alarm bell rings
>
> you can in fact use any "speaker wire" and wind that around a donut
> shaped ferrite core and have a (more or less) good choke ... so how
> can such a bifilar wound choke ... can take "no power" ?!? how did he
> connected it??
>
> next is ... a choke (or balun) should be have matched loads ... its
> not so well for high reactances ... the "j" value in the example .. is
> hifgher as the real part ...
>
But it is worth testing in a worst case environment. So you put, say,
100W into it from a 50 ohm source, and the voltage might be as much as
2*sqrt(100*50) - 140V (rms), 200V (peak).





> silver plating and shortwave?? ... rf wise shortwave is not so high
> that silver platig makes any difference in the balun
>
It's a heck of a lot easier to solder to silver (even tarnished) than to
copper (esp tarnished or oxidized).  Most high quality hookup wire has
silver plated strands (just a flash coat, but greatly improves
solderability)

Dragan Milivojevic 2021/01/27 02:59

https://youtu.be/dktDMnEGG0w?t=2190

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