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CMCs


David Eckhardt 2021/01/19 22:45

NOTE: The exceptionally high values of CM resistance are likely due to
resonances below my measurement window which has run from 1 MHz through 50
MHz. In de-Qing with a shunt 4.7k carbon resistor, the curves become much
flater and values pretty much between 1k and 2k. I noted the K9YC's data
increased as he increased frequency. Mine did not. I asked why. De-Qing
is likely the reason.

So, in practice, is there enough loss in the system, likely mostly earth
losses, to effectively de-Q the chokes? Neither of my wires are more than
35-feet off soil surface (decaying upper Permian mudstones).

Was the data presented by K9YC bifilar wound chokes or coaxial cable wound
on the ferrite toroids? I suspect they are with bifilar wound chokes. I
also have to wonder if K9YC de-Q'ed his chokes for measurement?

Also, after winding and testing the 31 materisl with solid #12 solid copper
wire, I am beginning to believe the losses in the stranded wire chokes I've
wound and tested are djue to the insulation. I'm going to tear down the
#10 stranded 43 material choke and rewind it with the solid #12 wire with
wider spaced turns, maybe no more than 8 or 10 turns on 2 stacked cores of
3" OD.

I've also ordered a couple of the 4" 31 material cores from KF78P
Metalworks which will be wound with the #12 solid copper wire. More
updates coming.
https://www.kf7p.com/KF7P/Welcome.html

PROBLEM with HOME BREW and TEST EQUIPMENT to MEASURE what YOU'VE
BUIILT.......... . . . NEVER SATISFIED............ All the chokes do a
good job of reducing the CM noise, but measurement shows the devil in the
details.....................

Dave - WØLEV

Siegfried Jackstien 2021/01/21 16:05

You measured the through loss... Ok

But not the common mode attenuation in db

For that connect only the shield with the hot end of your test jig.. If wound
with two parallel wires then connect only one of them...between the hot ends
of your test cables

Now measure s21

Greetz sigi dg9bfc





Am 19.01.2021 23:45 schrieb David Eckhardt <davearea51a@gmail.com>:

> NOTE: The exceptionally high values of CM resistance are likely due to
resonances below my measurement window which has run from 1 MHz through 50
MHz. In de-Qing with a shunt 4.7k carbon resistor, the curves become much
flater and values pretty much between 1k and 2k. I noted the K9YC's data
increased as he increased frequency. Mine did not. I asked why. De-Qing is
likely the reason.

>

>
>

>

> So, in practice, is there enough loss in the system, likely mostly earth
losses, to effectively de-Q the chokes? Neither of my wires are more than
35-feet off soil surface (decaying upper Permian mudstones).
>

>

>
>

>

> Was the data presented by K9YC bifilar wound chokes or coaxial cable wound
on the ferrite toroids? I suspect they are with bifilar wound chokes. I
also have to wonder if K9YC de-Q'ed his chokes for measurement?
>

>

>
>

>

> Also, after winding and testing the 31 materisl with solid #12 solid copper
wire, I am beginning to believe the losses in the stranded wire chokes I've
wound and tested are djue to the insulation. I'm going to tear down the #10
stranded 43 material choke and rewind it with the solid #12 wire with wider
spaced turns, maybe no more than 8 or 10 turns on 2 stacked cores of 3" OD.
>

>

>
>

>

> I've also ordered a couple of the 4" 31 material cores from KF78P Metalworks
which will be wound with the #12 solid copper wire. More updates coming.

>

> <https://www.kf7p.com/KF7P/Welcome.html>

>

>
>

>

> PROBLEM with HOME BREW and TEST EQUIPMENT to MEASURE what YOU'VE
BUIILT.......... . . . NEVER SATISFIED............ All the chokes do a good
job of reducing the CM noise, but measurement shows the devil in the
details.....................
>

>

>
>

>

> Dave - WØLEV
>

>

>
>



_._,_._,_

* * *

David Eckhardt 2021/01/21 17:55

In specifying a CMC choke, I have considered the CM impedance the choke
presents in my specific system. In considering that for my application, I
measured the complex impedance my antenna/feedline (open wire) presents in
the shack where I have the CMC installed (between the feeders and the
'input' of the L-network matching network, a.k.a.: antenna "tuner").
Knowing that, it's more important to know the CM impedance of the CMC than
attenuation in dB which is measured in a 50-ohm system. The
antenna/feedline is anything but 50 ± j 0 ohms. I'm using on all bands a
450-foot long doublet fed with a parallel conductor feedline. Excluding
40-meters, the impedance the CMC is installed ranges from 19 - j 288 at 2.0
MHz to 243 + j 227 at 14.25 MHz (I don't do much on the higher band). To
allow good performance at choking CM energy, I would prefer a CMC to
present at least 10X those impedances at the appropriate frequencies.
Given what I am dealing with, they all, so far, present at least 2.4 kΩ
impedance to the CM energy. I'd rather deal with things in that manner
than measure a dB attenuation as a function of frequency all measured in a
50 ± j 0 system in which my chokes are not installed. Nowhere in the
amateur bands do I 'see' 50-ohms with my antenna/feedline so I deem the
impedance measurement is more applicable than a dB attenuation of CM energy
in a 50-ohm system.

Dave - WØLEV

On Thu, Jan 21, 2021 at 3:06 PM Siegfried Jackstien <
siegfried.jackstien@freenet.de> wrote:

> You measured the through loss... Ok
> But not the common mode attenuation in db
> For that connect only the shield with the hot end of your test jig.. If
> wound with two parallel wires then connect only one of them...between the
> hot ends of your test cables
> Now measure s21
> Greetz sigi dg9bfc
>
>
> Am 19.01.2021 23:45 schrieb David Eckhardt <davearea51a@gmail.com>:
>
> NOTE: The exceptionally high values of CM resistance are likely due to
> resonances below my measurement window which has run from 1 MHz through 50
> MHz. In de-Qing with a shunt 4.7k carbon resistor, the curves become much
> flater and values pretty much between 1k and 2k. I noted the K9YC's data
> increased as he increased frequency. Mine did not. I asked why. De-Qing
> is likely the reason.
>
> So, in practice, is there enough loss in the system, likely mostly earth
> losses, to effectively de-Q the chokes? Neither of my wires are more than
> 35-feet off soil surface (decaying upper Permian mudstones).
>
> Was the data presented by K9YC bifilar wound chokes or coaxial cable wound
> on the ferrite toroids? I suspect they are with bifilar wound chokes. I
> also have to wonder if K9YC de-Q'ed his chokes for measurement?
>
> Also, after winding and testing the 31 materisl with solid #12 solid
> copper wire, I am beginning to believe the losses in the stranded wire
> chokes I've wound and tested are djue to the insulation. I'm going to tear
> down the #10 stranded 43 material choke and rewind it with the solid #12
> wire with wider spaced turns, maybe no more than 8 or 10 turns on 2 stacked
> cores of 3" OD.
>
> I've also ordered a couple of the 4" 31 material cores from KF78P
> Metalworks which will be wound with the #12 solid copper wire. More
> updates coming.
> https://www.kf7p.com/KF7P/Welcome.html
>
> PROBLEM with HOME BREW and TEST EQUIPMENT to MEASURE what YOU'VE
> BUIILT.......... . . . NEVER SATISFIED............ All the chokes do a
> good job of reducing the CM noise, but measurement shows the devil in the
> details.....................
>
> Dave - WØLEV
>
>
>
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

n2msqrp 2021/01/21 14:58

Dave,

Can you provide details of this CMC choke? Is you L-network an unbalanced tuner?

Mike N2MS

David Eckhardt 2021/01/21 20:58

Yes, it is an unbalanced matching network. That is the reason for placing
the CMC between the parallel line feeder and the "input" of the L-Network.
I used to use a balanced T-network and viewed it as a bilateral L-Network.
But a lot of experience, testing, reading, and measuring later, I realized
this was not the case. ONLY the L-Network exhibits one unique matching
point enabled by adjustment of its two reactive components presented it to
50 ± j 0 unlike the differential T and other network topologies. In
addition that singular matching adjustment of the two reactive elements is
at maximum efficiency of the network. Other networks do not necessarily
perform at maximum efficiency with their multiple matched adjustments of
the reactive elements of the network. One has no easy way of knowing the
other networks are adjusted for maximum efficiency along with a match to
50-ohms. Only the L-network can claim that feature.

Are you requesting details of the last CMC I wound with solid #12 enameled
copper wire on 2 stacked 31 material cores of 2.4" OD? This is the last
one on the right of the table. Just remember, the CM resistance will be
lower than the table indicated at the lower frequencies as I need to de-Q
the measurements. The measured DM losses will remain unchanged. Just let
me know and I'll write up that CMC, specifically.

Dave - WØLEV

On Thu, Jan 21, 2021 at 7:58 PM MICHAEL ST ANGELO <mstangelo@comcast.net>
wrote:

> Dave,
>
> Can you provide details of this CMC choke? Is you L-network an unbalanced
> tuner?
>
> Mike N2MS
>
> On 01/21/2021 12:55 PM David Eckhardt <davearea51a@gmail.com> wrote:
>
>
> In specifying a CMC choke, I have considered the CM impedance the choke
> presents in my specific system. In considering that for my application,
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

David Eckhardt 2021/01/22 00:09

I finally realized the 4.7 k carbon resistor is not de-Qing for which there
is no need. What I'm reading on the VNA is actually the parallel
combination of the resistor and the choke CM resistance. So the original
readings stand.

Dave - WØLEV

On Thu, Jan 21, 2021 at 8:58 PM David Eckhardt via groups.io <davearea51a=
gmail.com@groups.io> wrote:

> Yes, it is an unbalanced matching network. That is the reason for placing
> the CMC between the parallel line feeder and the "input" of the L-Network.
> I used to use a balanced T-network and viewed it as a bilateral L-Network.
> But a lot of experience, testing, reading, and measuring later, I realized
> this was not the case. ONLY the L-Network exhibits one unique matching
> point enabled by adjustment of its two reactive components presented it to
> 50 ± j 0 unlike the differential T and other network topologies. In
> addition that singular matching adjustment of the two reactive elements is
> at maximum efficiency of the network. Other networks do not necessarily
> perform at maximum efficiency with their multiple matched adjustments of
> the reactive elements of the network. One has no easy way of knowing the
> other networks are adjusted for maximum efficiency along with a match to
> 50-ohms. Only the L-network can claim that feature.
>
> Are you requesting details of the last CMC I wound with solid #12 enameled
> copper wire on 2 stacked 31 material cores of 2.4" OD? This is the last
> one on the right of the table. Just remember, the CM resistance will be
> lower than the table indicated at the lower frequencies as I need to de-Q
> the measurements. The measured DM losses will remain unchanged. Just let
> me know and I'll write up that CMC, specifically.
>
> Dave - WØLEV
>
> On Thu, Jan 21, 2021 at 7:58 PM MICHAEL ST ANGELO <mstangelo@comcast.net>
> wrote:
>
>> Dave,
>>
>> Can you provide details of this CMC choke? Is you L-network an unbalanced
>> tuner?
>>
>> Mike N2MS
>>
>> On 01/21/2021 12:55 PM David Eckhardt <davearea51a@gmail.com> wrote:
>>
>>
>> In specifying a CMC choke, I have considered the CM impedance the choke
>> presents in my specific system. In considering that for my application,
>>
>>
>
> --
> *Dave - WØLEV*
> *Just Let Darwin Work*
>
>
>
>

--
*Dave - WØLEV*
*Just Let Darwin Work*

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