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50 ohms to 0.02 ohm transformer

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  50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 07:55 -0500
    Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-03 15:12 +0200
      Re: 50 ohms to 0.02 ohm transformer John Larkin <jjlarkin@highlandtechnology.com> - 2016-11-03 10:55 -0700
        Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 16:56 -0500
          Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 20:36 -0500
          Re: 50 ohms to 0.02 ohm transformer Syd Rumpo <usenet@nononono.co.uk> - 2016-11-08 23:35 +0000
          Re: 50 ohms to 0.02 ohm transformer Lasse Langwadt Christensen <langwadt@fonz.dk> - 2016-11-08 15:51 -0800
            Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-08 21:45 -0600
            Re: 50 ohms to 0.02 ohm transformer Jasen Betts <jasen@xnet.co.nz> - 2016-11-10 03:28 +0000
        Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-04 10:41 +0200
          Re: 50 ohms to 0.02 ohm transformer Jeroen Belleman <jeroen@nospam.please> - 2016-11-04 10:54 +0100
        Re: 50 ohms to 0.02 ohm transformer bill.sloman@ieee.org - 2016-11-04 06:00 -0700
          Re: 50 ohms to 0.02 ohm transformer Jeroen Belleman <jeroen@nospam.please> - 2016-11-04 14:10 +0100
            Re: 50 ohms to 0.02 ohm transformer John Larkin <jjlarkin@highlandtechnology.com> - 2016-11-04 08:08 -0700
        Re: 50 ohms to 0.02 ohm transformer "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-11-04 22:13 -0500
    Re: 50 ohms to 0.02 ohm transformer Jeroen Belleman <jeroen@nospam.please> - 2016-11-03 14:58 +0100
      Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 09:57 -0500
        Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 09:59 -0500
        Re: 50 ohms to 0.02 ohm transformer Tim Wescott <seemywebsite@myfooter.really> - 2016-11-03 11:56 -0500
          Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 12:15 -0500
            Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-03 19:37 +0200
              Re: 50 ohms to 0.02 ohm transformer makolber@yahoo.com - 2016-11-03 10:49 -0700
              Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 13:19 -0500
              Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 13:31 -0500
                Re: 50 ohms to 0.02 ohm transformer Tim Wescott <seemywebsite@myfooter.really> - 2016-11-03 14:38 -0500
              Re: 50 ohms to 0.02 ohm transformer Tim Wescott <seemywebsite@myfooter.really> - 2016-11-03 14:39 -0500
                Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-03 16:52 -0500
                  Re: 50 ohms to 0.02 ohm transformer whit3rd <whit3rd@gmail.com> - 2016-11-03 18:00 -0700
                Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-04 06:26 -0500
                  Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-04 15:20 +0200
                    Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-04 09:33 -0500
                      Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-04 21:21 +0200
            Re: 50 ohms to 0.02 ohm transformer "tom" <tmiller11147@verizon.net> - 2016-11-03 14:02 -0400
    Re: 50 ohms to 0.02 ohm transformer Winfield Hill <hill@rowland.harvard.edu> - 2016-11-03 10:25 -0700
    Re: 50 ohms to 0.02 ohm transformer Jeff Liebermann <jeffl@cruzio.com> - 2016-11-04 11:24 -0700
      Re: 50 ohms to 0.02 ohm transformer Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-11-04 21:24 +0200
        Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-04 16:46 -0500
          Re: 50 ohms to 0.02 ohm transformer amdx <nojunk@knology.net> - 2016-11-05 12:37 -0500
    Re: 50 ohms to 0.02 ohm transformer mike <ham789@netzero.net> - 2016-11-05 02:29 -0700

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#433614 — 50 ohms to 0.02 ohm transformer

I want to build a 50 ohm to 0.02 ohm transformer.
It needs a 50 to 1 turns ratio.
  It takes a low A sub L core to make such a thing.
I have a toroid with an A sub L of 75. That only needs
29 turns for my frequency of interest 500KHz to 1700kHz.
I also have some potcores that I could gap to lower the A sub L.

What would make a better transformer a toroid or a gapped potcore?

  I plan 50 turns with a 1 turn secondary.

What problems can I expect with a 1 turn secondary?

                         Thanks,     Mikek

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#433615

On 3.11.16 14:55, amdx wrote:
> I want to build a 50 ohm to 0.02 ohm transformer.
> It needs a 50 to 1 turns ratio.
>  It takes a low A sub L core to make such a thing.
> I have a toroid with an A sub L of 75. That only needs
> 29 turns for my frequency of interest 500KHz to 1700kHz.
> I also have some potcores that I could gap to lower the A sub L.
>
> What would make a better transformer a toroid or a gapped potcore?
>
>  I plan 50 turns with a 1 turn secondary.
>
> What problems can I expect with a 1 turn secondary?
>
>                         Thanks,     Mikek

For a toroid, a turn is simple: A wire through the toroid
hole is a turn, a wire outside is nothing.

IMHO, your real problem is on the 20 milliohm side to make
the circuit connections so that you're not going to lose all
of your signal in the connection resistances and inductances.
This is regardless which way you build your transformer.

-- 

-TV

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#433684

On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:

>On 3.11.16 14:55, amdx wrote:
>> I want to build a 50 ohm to 0.02 ohm transformer.
>> It needs a 50 to 1 turns ratio.
>>  It takes a low A sub L core to make such a thing.
>> I have a toroid with an A sub L of 75. That only needs
>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>> I also have some potcores that I could gap to lower the A sub L.
>>
>> What would make a better transformer a toroid or a gapped potcore?
>>
>>  I plan 50 turns with a 1 turn secondary.
>>
>> What problems can I expect with a 1 turn secondary?
>>
>>                         Thanks,     Mikek
>
>For a toroid, a turn is simple: A wire through the toroid
>hole is a turn, a wire outside is nothing.
>
>IMHO, your real problem is on the 20 milliohm side to make
>the circuit connections so that you're not going to lose all
>of your signal in the connection resistances and inductances.
>This is regardless which way you build your transformer.

Leakage inductance can matter.

It would be interesting to make a toroidal transformer where the
1-turn winding wraps around the entire core. Visualize that! It can be
approximated by paralleling multiple 1t windings.

http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#433735

On 11/3/2016 12:55 PM, John Larkin wrote:
> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
> <tauno.voipio@notused.fi.invalid> wrote:
>
>> On 3.11.16 14:55, amdx wrote:
>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>> It needs a 50 to 1 turns ratio.
>>>  It takes a low A sub L core to make such a thing.
>>> I have a toroid with an A sub L of 75. That only needs
>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>> I also have some potcores that I could gap to lower the A sub L.
>>>
>>> What would make a better transformer a toroid or a gapped potcore?
>>>
>>>  I plan 50 turns with a 1 turn secondary.
>>>
>>> What problems can I expect with a 1 turn secondary?
>>>
>>>                         Thanks,     Mikek
>>
>> For a toroid, a turn is simple: A wire through the toroid
>> hole is a turn, a wire outside is nothing.
>>
>> IMHO, your real problem is on the 20 milliohm side to make
>> the circuit connections so that you're not going to lose all
>> of your signal in the connection resistances and inductances.
>> This is regardless which way you build your transformer.
>
> Leakage inductance can matter.
>
> It would be interesting to make a toroidal transformer where the
> 1-turn winding wraps around the entire core. Visualize that! It can be
> approximated by paralleling multiple 1t windings.
>
> http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg
>
>


   Hows this John,

> https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0

> https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0

  I haven't tested it yet.

                           Mikek

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#433776

On 11/3/2016 4:56 PM, amdx wrote:
> On 11/3/2016 12:55 PM, John Larkin wrote:
>> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
>> <tauno.voipio@notused.fi.invalid> wrote:
>>
>>> On 3.11.16 14:55, amdx wrote:
>>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>>> It needs a 50 to 1 turns ratio.
>>>>  It takes a low A sub L core to make such a thing.
>>>> I have a toroid with an A sub L of 75. That only needs
>>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>>> I also have some potcores that I could gap to lower the A sub L.
>>>>
>>>> What would make a better transformer a toroid or a gapped potcore?
>>>>
>>>>  I plan 50 turns with a 1 turn secondary.
>>>>
>>>> What problems can I expect with a 1 turn secondary?
>>>>
>>>>                         Thanks,     Mikek
>>>
>>> For a toroid, a turn is simple: A wire through the toroid
>>> hole is a turn, a wire outside is nothing.
>>>
>>> IMHO, your real problem is on the 20 milliohm side to make
>>> the circuit connections so that you're not going to lose all
>>> of your signal in the connection resistances and inductances.
>>> This is regardless which way you build your transformer.
>>
>> Leakage inductance can matter.
>>
>> It would be interesting to make a toroidal transformer where the
>> 1-turn winding wraps around the entire core. Visualize that! It can be
>> approximated by paralleling multiple 1t windings.
>>
>> http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg
>>
>>
>>
>
>
>   Hows this John,
>
>> https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0
>>
>
>> https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0
>>
>
>  I haven't tested it yet.
>
>                           Mikek

  My transformer, with the one turn winding open, looks great.
10vpp in 200mvpp out exactly 50 to 1 ratio.
However, when I load it with  0.02 ohms (a 15 in wire)
it barely changes amplitude, and the primary amplitude also doesn't 
change. If 50 ohms was reflected back it would drop by 1/2.
  Shorting the secondary one turn with a pair of needle nose pliers
drops the secondary voltage about 10%.
  Time to sleep on it.
                       Later, Mikek

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#434303

On 03/11/2016 21:56, amdx wrote:

<snip>

>
>   Hows this John,
>
>> https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0
>>
>
>> https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0
>>
>
>  I haven't tested it yet.
>
>                           Mikek

I can't see the first one, but that second picture makes me want one. 
All I need now is a reason...

Cheers
-- 
Syd

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#434311

Den torsdag den 3. november 2016 kl. 22.56.41 UTC+1 skrev amdx:
> On 11/3/2016 12:55 PM, John Larkin wrote:
> > On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
> > <tauno.voipio@notused.fi.invalid> wrote:
> >
> >> On 3.11.16 14:55, amdx wrote:
> >>> I want to build a 50 ohm to 0.02 ohm transformer.
> >>> It needs a 50 to 1 turns ratio.
> >>>  It takes a low A sub L core to make such a thing.
> >>> I have a toroid with an A sub L of 75. That only needs
> >>> 29 turns for my frequency of interest 500KHz to 1700kHz.
> >>> I also have some potcores that I could gap to lower the A sub L.
> >>>
> >>> What would make a better transformer a toroid or a gapped potcore?
> >>>
> >>>  I plan 50 turns with a 1 turn secondary.
> >>>
> >>> What problems can I expect with a 1 turn secondary?
> >>>
> >>>                         Thanks,     Mikek
> >>
> >> For a toroid, a turn is simple: A wire through the toroid
> >> hole is a turn, a wire outside is nothing.
> >>
> >> IMHO, your real problem is on the 20 milliohm side to make
> >> the circuit connections so that you're not going to lose all
> >> of your signal in the connection resistances and inductances.
> >> This is regardless which way you build your transformer.
> >
> > Leakage inductance can matter.
> >
> > It would be interesting to make a toroidal transformer where the
> > 1-turn winding wraps around the entire core. Visualize that! It can be
> > approximated by paralleling multiple 1t windings.
> >
> > http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg
> >
> >
> 
> 
>    Hows this John,
> 
> > https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0
> 
> > https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0
> 
>   I haven't tested it yet.
> 
>                            Mikek

I wonder if it would be an advantage to split the ring opposite the 
wire connection so it isn't a closed closed loop

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#434344

On 11/8/2016 5:51 PM, Lasse Langwadt Christensen wrote:
> Den torsdag den 3. november 2016 kl. 22.56.41 UTC+1 skrev amdx:
>> On 11/3/2016 12:55 PM, John Larkin wrote:
>>> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
>>> <tauno.voipio@notused.fi.invalid> wrote:
>>>
>>>> On 3.11.16 14:55, amdx wrote:
>>>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>>>> It needs a 50 to 1 turns ratio.
>>>>>  It takes a low A sub L core to make such a thing.
>>>>> I have a toroid with an A sub L of 75. That only needs
>>>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>>>> I also have some potcores that I could gap to lower the A sub L.
>>>>>
>>>>> What would make a better transformer a toroid or a gapped potcore?
>>>>>
>>>>>  I plan 50 turns with a 1 turn secondary.
>>>>>
>>>>> What problems can I expect with a 1 turn secondary?
>>>>>
>>>>>                         Thanks,     Mikek
>>>>
>>>> For a toroid, a turn is simple: A wire through the toroid
>>>> hole is a turn, a wire outside is nothing.
>>>>
>>>> IMHO, your real problem is on the 20 milliohm side to make
>>>> the circuit connections so that you're not going to lose all
>>>> of your signal in the connection resistances and inductances.
>>>> This is regardless which way you build your transformer.
>>>
>>> Leakage inductance can matter.
>>>
>>> It would be interesting to make a toroidal transformer where the
>>> 1-turn winding wraps around the entire core. Visualize that! It can be
>>> approximated by paralleling multiple 1t windings.
>>>
>>> http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg
>>>
>>>
>>
>>
>>    Hows this John,
>>
>>> https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0
>>
>>> https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0
>>
>>   I haven't tested it yet.
>>
>>                            Mikek
>
> I wonder if it would be an advantage to split the ring opposite the
> wire connection so it isn't a closed closed loop
>

  I wondered that also.
  btw, the wires you see are for the 50 turn primary connection.
For the one turn secondary, the connections can be anywhere around the
circumference to the two buss bars. (16gauge wire)
                   Mikek

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#434644

On 2016-11-08, Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:
> Den torsdag den 3. november 2016 kl. 22.56.41 UTC+1 skrev amdx:
>> On 11/3/2016 12:55 PM, John Larkin wrote:
>> > On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
>> > <tauno.voipio@notused.fi.invalid> wrote:
>> >
>> >> On 3.11.16 14:55, amdx wrote:
>> >>> I want to build a 50 ohm to 0.02 ohm transformer.
>> >>> It needs a 50 to 1 turns ratio.
>> >>>  It takes a low A sub L core to make such a thing.
>> >>> I have a toroid with an A sub L of 75. That only needs
>> >>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>> >>> I also have some potcores that I could gap to lower the A sub L.
>> >>>
>> >>> What would make a better transformer a toroid or a gapped potcore?
>> >>>
>> >>>  I plan 50 turns with a 1 turn secondary.
>> >>>
>> >>> What problems can I expect with a 1 turn secondary?
>> >>>
>> >>>                         Thanks,     Mikek
>> >>
>> >> For a toroid, a turn is simple: A wire through the toroid
>> >> hole is a turn, a wire outside is nothing.
>> >>
>> >> IMHO, your real problem is on the 20 milliohm side to make
>> >> the circuit connections so that you're not going to lose all
>> >> of your signal in the connection resistances and inductances.
>> >> This is regardless which way you build your transformer.
>> >
>> > Leakage inductance can matter.
>> >
>> > It would be interesting to make a toroidal transformer where the
>> > 1-turn winding wraps around the entire core. Visualize that! It can be
>> > approximated by paralleling multiple 1t windings.
>> >
>> > http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg
>> >
>> >
>> 
>> 
>>    Hows this John,
>> 
>> > https://www.dropbox.com/s/6klg2v2awamchb5/2001-12-31%2023.00.00-122.jpg?dl=0
>> 
>> > https://www.dropbox.com/s/3gmnukf4u7kawx3/2001-12-31%2023.00.00-120.jpg?dl=0
>> 
>>   I haven't tested it yet.
>> 
>>                            Mikek
>
> I wonder if it would be an advantage to split the ring opposite the 
> wire connection so it isn't a closed closed loop

Probably not. My thoughts, this way if the 50 turns primary is 
progressive its parasitic single turn will see a shorted turn, 
thus improing EMI shielding.


-- 
This email has not been checked by half-arsed antivirus software 

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#433812

On 3.11.16 19:55, John Larkin wrote:
>> This is regardless which way you build your transformer.
>
> Leakage inductance can matter.
>
> It would be interesting to make a toroidal transformer where the
> 1-turn winding wraps around the entire core. Visualize that! It can be
> approximated by paralleling multiple 1t windings.
>
> http://www.spaceneedle.com/wp-content/uploads/2013/08/view-from-heli-250x211.jpg


It has been for years a common practice in transistor RF amplifiers
to make the single-turn windings of copper/brass tubing and threading
the multiple-turn winding through the tube inside. This probably
is like your paralleled windings.

In recent ARRL Handbooks there are fine examples (in 2014 edition
on page 17.32).

-- 

-TV

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#433820

  On 3.11.16 19:55, John Larkin wrote:
>
> Leakage inductance can matter.
>
> It would be interesting to make a toroidal transformer where the
> 1-turn winding wraps around the entire core. Visualize that! It can be
> approximated by paralleling multiple 1t windings.

I build 'wall current monitors' to measure the beam
current in particle accelerators. Those are basically
single-turn transformers very much like that: The
secondary winding is a toroidal shell completely
enveloping the core, with a small gap across which I
pick-up the output signal. Accessorily, the secondary
winding is also the vacuum chamber.

I also make hybrid transformers that basically create
the sum and difference of two input signals on two
separate outputs. One of the issues limiting performance
at HF is the capacitance between the two input windings
and the difference winding. I tried putting the
difference winding on its own separate core, and then
coupling the two cores with a single-turn winding threading
both. This was in practice a piece of air core coax
shorted at both ends, with the two cores inside. It worked,
but it wasn't enough of an improvement to be worth the
bother.

Jeroen Belleman

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#433830

On Friday, November 4, 2016 at 4:55:39 AM UTC+11, John Larkin wrote:
> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
> <tauno.voipio@notused.fi.invalid> wrote:
> 
> >On 3.11.16 14:55, amdx wrote:
> >> I want to build a 50 ohm to 0.02 ohm transformer.
> >> It needs a 50 to 1 turns ratio.
> >>  It takes a low A sub L core to make such a thing.
> >> I have a toroid with an A sub L of 75. That only needs
> >> 29 turns for my frequency of interest 500KHz to 1700kHz.
> >> I also have some potcores that I could gap to lower the A sub L.
> >>
> >> What would make a better transformer a toroid or a gapped potcore?
> >>
> >>  I plan 50 turns with a 1 turn secondary.
> >>
> >> What problems can I expect with a 1 turn secondary?
> >>
> >>                         Thanks,     Mikek
> >
> >For a toroid, a turn is simple: A wire through the toroid
> >hole is a turn, a wire outside is nothing.
> >
> >IMHO, your real problem is on the 20 milliohm side to make
> >the circuit connections so that you're not going to lose all
> >of your signal in the connection resistances and inductances.
> >This is regardless which way you build your transformer.
> 
> Leakage inductance can matter.
> 
> It would be interesting to make a toroidal transformer where the
> 1-turn winding wraps around the entire core. Visualize that! It can be
> approximated by paralleling multiple 1t windings.

The problem with making a 1-turn winding on a toroid would be making it non-progressive.

As long as you have a turn in the plane of the toroid, you've got an external field and leakage inductance. 

The tricks for making non-progressive winding do seem to involve a second turn going back around the toroid in the opposite sense (viewed from above the plane of toroid).

-- 
Bill Sloman, Sydney

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#433831

On 2016-11-04 14:00, bill.sloman@ieee.org wrote:
> On Friday, November 4, 2016 at 4:55:39 AM UTC+11, John Larkin wrote:
>> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
>> <tauno.voipio@notused.fi.invalid> wrote:
>>
>>> On 3.11.16 14:55, amdx wrote:
>>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>>> It needs a 50 to 1 turns ratio.
>>>>   It takes a low A sub L core to make such a thing.
>>>> I have a toroid with an A sub L of 75. That only needs
>>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>>> I also have some potcores that I could gap to lower the A sub L.
>>>>
>>>> What would make a better transformer a toroid or a gapped potcore?
>>>>
>>>>   I plan 50 turns with a 1 turn secondary.
>>>>
>>>> What problems can I expect with a 1 turn secondary?
>>>>
>>>>                          Thanks,     Mikek
>>>
>>> For a toroid, a turn is simple: A wire through the toroid
>>> hole is a turn, a wire outside is nothing.
>>>
>>> IMHO, your real problem is on the 20 milliohm side to make
>>> the circuit connections so that you're not going to lose all
>>> of your signal in the connection resistances and inductances.
>>> This is regardless which way you build your transformer.
>>
>> Leakage inductance can matter.
>>
>> It would be interesting to make a toroidal transformer where the
>> 1-turn winding wraps around the entire core. Visualize that! It can be
>> approximated by paralleling multiple 1t windings.
>
> The problem with making a 1-turn winding on a toroid would be
> making it non-progressive.

I fail to see how a one-turn winding that wraps around the entire
core can be progressive. A multi-turn progressive winding, yes,
but a single-turn winding has no current in the plane of the toroid.
Making proper connections to such a winding may be challenging.

Jeroen Belleman

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#433853

On Fri, 04 Nov 2016 14:10:16 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 2016-11-04 14:00, bill.sloman@ieee.org wrote:
>> On Friday, November 4, 2016 at 4:55:39 AM UTC+11, John Larkin wrote:
>>> On Thu, 3 Nov 2016 15:12:53 +0200, Tauno Voipio
>>> <tauno.voipio@notused.fi.invalid> wrote:
>>>
>>>> On 3.11.16 14:55, amdx wrote:
>>>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>>>> It needs a 50 to 1 turns ratio.
>>>>>   It takes a low A sub L core to make such a thing.
>>>>> I have a toroid with an A sub L of 75. That only needs
>>>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>>>> I also have some potcores that I could gap to lower the A sub L.
>>>>>
>>>>> What would make a better transformer a toroid or a gapped potcore?
>>>>>
>>>>>   I plan 50 turns with a 1 turn secondary.
>>>>>
>>>>> What problems can I expect with a 1 turn secondary?
>>>>>
>>>>>                          Thanks,     Mikek
>>>>
>>>> For a toroid, a turn is simple: A wire through the toroid
>>>> hole is a turn, a wire outside is nothing.
>>>>
>>>> IMHO, your real problem is on the 20 milliohm side to make
>>>> the circuit connections so that you're not going to lose all
>>>> of your signal in the connection resistances and inductances.
>>>> This is regardless which way you build your transformer.
>>>
>>> Leakage inductance can matter.
>>>
>>> It would be interesting to make a toroidal transformer where the
>>> 1-turn winding wraps around the entire core. Visualize that! It can be
>>> approximated by paralleling multiple 1t windings.
>>
>> The problem with making a 1-turn winding on a toroid would be
>> making it non-progressive.
>
>I fail to see how a one-turn winding that wraps around the entire
>core can be progressive. A multi-turn progressive winding, yes,
>but a single-turn winding has no current in the plane of the toroid.
>Making proper connections to such a winding may be challenging.
>
>Jeroen Belleman

Make a bunch of 1-turn secondaries, each driving a twisted pair.
Connect the pairs outside the plane of the toroid. Like the Space
Needle.

I had dinner in the Space Needle once. The tables rotate around on a
track to slowly to scan the view. If you lean your elbow on the window
sill, it slowly creeps out from under you. If you go the the bathroom
and then go again later, it's in a different direction.

I guess the Space Needle has low leakage inductance.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

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#433942

"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message 
news:4aum1c1gog519isp42g1hhcac03beg96ki@4ax.com...
> Leakage inductance can matter.
>

Out of 0.02 ohms, that's a guarantee!

Out of 50 ohms, a pretty good match should be reasonable, up to whatever the 
electrical length of the primary winding is (at which point it looks like a 
transmission line over the secondary "ground plane").


> It would be interesting to make a toroidal transformer where the
> 1-turn winding wraps around the entire core. Visualize that! It can be
> approximated by paralleling multiple 1t windings.

Easy enough.  This is a cross section.  Imagine it's revolved around the 
axis on the right (so the gray core part is a torus, and everything else is 
a disk, cylinder or hole shape).
http://seventransistorlabs.com/Images/OPT_XSection.png
Oh, the copper colored vertical sides connect to a plate shorting across the 
top, of course.

I'd show a picture of the finished thing, but it's pretty boring, like 
looking at a bank vault from the "concrete walls" side. :^)

Or if you want an inline structure (like a coaxial current transformer), you 
start with a pipe, slit it, then put a larger pipe on over the slit (with 
discs to short it to the first pipe, on either side of the slit).  The core 
and windings go inside the space thus created.


In particle accelerators, the bunches are so small (sub-ns) that they can't 
afford any windings at all; transmission lines are simply connected in 
parallel across the gap!

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

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#433623

On 2016-11-03 13:55, amdx wrote:
> I want to build a 50 ohm to 0.02 ohm transformer.
> It needs a 50 to 1 turns ratio.
>   It takes a low A sub L core to make such a thing.
> I have a toroid with an A sub L of 75. That only needs
> 29 turns for my frequency of interest 500KHz to 1700kHz.
> I also have some potcores that I could gap to lower the A sub L.
>
> What would make a better transformer a toroid or a gapped potcore?
>
>   I plan 50 turns with a 1 turn secondary.
>
> What problems can I expect with a 1 turn secondary?
>
>                          Thanks,     Mikek

A bandwidth ratio of only three should be dead-easy,
but the 20 mOhm impedance may spell trouble.
The single-turn winding should be fat and compact.
A single nH of stray inductance (!) or ten mOhms
of resistance would ruin performance. I think I would
implement it as several single-turn windings in parallel,
distributed around a toroid. What will you connect
to the 20mOhm side?

Why would you need low A_l? The usual rule of having the
reactance of one winding four times the terminal impedance
is only a minimum. There is no harm in going higher. There
would be if you did it by using more turns though.

Use a toroid. Gapped cores are for energy storage,
not for transformers.

Jeroen Belleman

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#433628

On 11/3/2016 8:58 AM, Jeroen Belleman wrote:
> On 2016-11-03 13:55, amdx wrote:
>> I want to build a 50 ohm to 0.02 ohm transformer.
>> It needs a 50 to 1 turns ratio.
>>   It takes a low A sub L core to make such a thing.
>> I have a toroid with an A sub L of 75. That only needs
>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>> I also have some potcores that I could gap to lower the A sub L.
>>
>> What would make a better transformer a toroid or a gapped potcore?
>>
>>   I plan 50 turns with a 1 turn secondary.
>>
>> What problems can I expect with a 1 turn secondary?
>>
>>                          Thanks,     Mikek
>
> A bandwidth ratio of only three should be dead-easy,
> but the 20 mOhm impedance may spell trouble.
> The single-turn winding should be fat and compact.
> A single nH of stray inductance (!) or ten mOhms
> of resistance would ruin performance. I think I would
> implement it as several single-turn windings in parallel,
> distributed around a toroid. What will you connect
> to the 20mOhm side?

  A 20mOhm resistor.
   I'm replacing a tube osc, I'm not able to follow the coax back to the 
tube output on the schematic, so I don't even have a start to figure out 
the tube output impedance. I'm starting to think it is not low.
  But it is able to drive 1 amp through the 0.02 ohm resistor to develop
20mv.



> Why would you need low A_l? The usual rule of having the
> reactance of one winding four times the terminal impedance
> is only a minimum. There is no harm in going higher. There
> would be if you did it by using more turns though.
>

My calculations tell me that with an AsubL of 75 it take 29 turns.
This still doesn't get my a 50 to 1 turn ratio.
If I use a core with an AsubL of 2340, I only need 5 turns, with that I 
can't get a 50 to 1 turns ratio.

> Use a toroid. Gapped cores are for energy storage,
> not for transformers.
>
> Jeroen Belleman

  I'll restate my problem,
I want to substitute a more stable signal generator for the internal
signal generator in my Boonton 260A Q meter. The osc. in the 260A drives
a 0.02 ohm resistor. It actually does this through a piece of coax,
so I doubt it really has a 0.02 ohm output impedance. Could be I'm 
chasing a spec. I don't need to.
  One advantage I have is I only want 4mv of drive across the 0.02 ohm 
resistor, also I can adjust the signal generator output to set the 
voltage regardless of transformer/connection losses.
   Thanks for the multiple single turn winding in parallel idea.
                             Still open to suggestions,
                                          Thanks, Mikek

PS.
Next project is an RF detector to measure the 4mv signal, I want a 
circuit to drive my multimeter. I suspect I'll need a preamp before the 
detector to get any linearity. I do have a scope I can use to get a 
useful calibration.

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#433629

On 11/3/2016 9:57 AM, amdx wrote:
> On 11/3/2016 8:58 AM, Jeroen Belleman wrote:
>> On 2016-11-03 13:55, amdx wrote:
>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>> It needs a 50 to 1 turns ratio.
>>>   It takes a low A sub L core to make such a thing.
>>> I have a toroid with an A sub L of 75. That only needs
>>> 29 turns for my frequency of interest 500KHz to 1700kHz.
>>> I also have some potcores that I could gap to lower the A sub L.
>>>
>>> What would make a better transformer a toroid or a gapped potcore?
>>>
>>>   I plan 50 turns with a 1 turn secondary.
>>>
>>> What problems can I expect with a 1 turn secondary?
>>>
>>>                          Thanks,     Mikek
>>
>> A bandwidth ratio of only three should be dead-easy,
>> but the 20 mOhm impedance may spell trouble.
>> The single-turn winding should be fat and compact.
>> A single nH of stray inductance (!) or ten mOhms
>> of resistance would ruin performance. I think I would
>> implement it as several single-turn windings in parallel,
>> distributed around a toroid. What will you connect
>> to the 20mOhm side?
>
>  A 20mOhm resistor.
>   I'm replacing a tube osc, I'm not able to follow the coax back to the
> tube output on the schematic, so I don't even have a start to figure out
> the tube output impedance. I'm starting to think it is not low.
>  But it is able to drive 1 amp through the 0.02 ohm resistor to develop
> 20mv.
>
    I meant to add there is a schematic on the last page of this pdf.
> http://www.hparchive.com/Boonton/Boonton-Manual-260A.pdf

Maybe you can see how the tube output gets to the coax. :-)

>
>
>> Why would you need low A_l? The usual rule of having the
>> reactance of one winding four times the terminal impedance
>> is only a minimum. There is no harm in going higher. There
>> would be if you did it by using more turns though.
>>
>
> My calculations tell me that with an AsubL of 75 it take 29 turns.
> This still doesn't get my a 50 to 1 turn ratio.
> If I use a core with an AsubL of 2340, I only need 5 turns, with that I
> can't get a 50 to 1 turns ratio.
>
>> Use a toroid. Gapped cores are for energy storage,
>> not for transformers.
>>
>> Jeroen Belleman
>
>  I'll restate my problem,
> I want to substitute a more stable signal generator for the internal
> signal generator in my Boonton 260A Q meter. The osc. in the 260A drives
> a 0.02 ohm resistor. It actually does this through a piece of coax,
> so I doubt it really has a 0.02 ohm output impedance. Could be I'm
> chasing a spec. I don't need to.
>  One advantage I have is I only want 4mv of drive across the 0.02 ohm
> resistor, also I can adjust the signal generator output to set the
> voltage regardless of transformer/connection losses.
>   Thanks for the multiple single turn winding in parallel idea.
>                             Still open to suggestions,
>                                          Thanks, Mikek
>
> PS.
> Next project is an RF detector to measure the 4mv signal, I want a
> circuit to drive my multimeter. I suspect I'll need a preamp before the
> detector to get any linearity. I do have a scope I can use to get a
> useful calibration.
>
>

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#433657

On Thu, 03 Nov 2016 09:57:09 -0500, amdx wrote:

> On 11/3/2016 8:58 AM, Jeroen Belleman wrote:
>> On 2016-11-03 13:55, amdx wrote:
>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>> It needs a 50 to 1 turns ratio.
>>>   It takes a low A sub L core to make such a thing.
>>> I have a toroid with an A sub L of 75. That only needs 29 turns for my
>>> frequency of interest 500KHz to 1700kHz.
>>> I also have some potcores that I could gap to lower the A sub L.
>>>
>>> What would make a better transformer a toroid or a gapped potcore?
>>>
>>>   I plan 50 turns with a 1 turn secondary.
>>>
>>> What problems can I expect with a 1 turn secondary?
>>>
>>>                          Thanks,     Mikek
>>
>> A bandwidth ratio of only three should be dead-easy,
>> but the 20 mOhm impedance may spell trouble.
>> The single-turn winding should be fat and compact.
>> A single nH of stray inductance (!) or ten mOhms of resistance would
>> ruin performance. I think I would implement it as several single-turn
>> windings in parallel, distributed around a toroid. What will you
>> connect to the 20mOhm side?
> 
>   A 20mOhm resistor.
>    I'm replacing a tube osc, I'm not able to follow the coax back to the
> tube output on the schematic, so I don't even have a start to figure out
> the tube output impedance. I'm starting to think it is not low.
>   But it is able to drive 1 amp through the 0.02 ohm resistor to develop
> 20mv.
> 
> 
> 
>> Why would you need low A_l? The usual rule of having the reactance of
>> one winding four times the terminal impedance is only a minimum. There
>> is no harm in going higher. There would be if you did it by using more
>> turns though.
>>
>>
> My calculations tell me that with an AsubL of 75 it take 29 turns.
> This still doesn't get my a 50 to 1 turn ratio.
> If I use a core with an AsubL of 2340, I only need 5 turns, with that I
> can't get a 50 to 1 turns ratio.
> 
>> Use a toroid. Gapped cores are for energy storage,
>> not for transformers.
>>
>> Jeroen Belleman
> 
>   I'll restate my problem,
> I want to substitute a more stable signal generator for the internal
> signal generator in my Boonton 260A Q meter. The osc. in the 260A drives
> a 0.02 ohm resistor. It actually does this through a piece of coax,
> so I doubt it really has a 0.02 ohm output impedance. Could be I'm
> chasing a spec. I don't need to.
>   One advantage I have is I only want 4mv of drive across the 0.02 ohm
> resistor, also I can adjust the signal generator output to set the
> voltage regardless of transformer/connection losses.
>    Thanks for the multiple single turn winding in parallel idea.
>                              Still open to suggestions,
>                                           Thanks, Mikek
> 
> PS.
> Next project is an RF detector to measure the 4mv signal, I want a
> circuit to drive my multimeter. I suspect I'll need a preamp before the
> detector to get any linearity. I do have a scope I can use to get a
> useful calibration.

Your calculations show you that you need a _minimum_ of 29 turns, not 
_exactly_ 29 turns.  29 is less than 50, so if you feel bound and 
determined to maintain that ratio, use 50 turns and be happy.

What's probably a better way (and what's probably being done in the 
meter) is to not bother matching to that resistor, but rather to build an 
amplifier that can work into a low impedance (or whatever the impedance 
is when transformed by that coax and whatever is ahead of it), and just 
accept whatever inefficiencies result.

If all you want is for the thing to generally operate the way it does now 
but with a more stable oscillator, you may be best served by either 
turning the current oscillator into an amplifier stage to be driven by 
your oscillator, or injection-locking it.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

I'm looking for work -- see my website!

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#433662

On 11/3/2016 11:56 AM, Tim Wescott wrote:
> On Thu, 03 Nov 2016 09:57:09 -0500, amdx wrote:
>
>> On 11/3/2016 8:58 AM, Jeroen Belleman wrote:
>>> On 2016-11-03 13:55, amdx wrote:
>>>> I want to build a 50 ohm to 0.02 ohm transformer.
>>>> It needs a 50 to 1 turns ratio.
>>>>   It takes a low A sub L core to make such a thing.
>>>> I have a toroid with an A sub L of 75. That only needs 29 turns for my
>>>> frequency of interest 500KHz to 1700kHz.
>>>> I also have some potcores that I could gap to lower the A sub L.
>>>>
>>>> What would make a better transformer a toroid or a gapped potcore?
>>>>
>>>>   I plan 50 turns with a 1 turn secondary.
>>>>
>>>> What problems can I expect with a 1 turn secondary?
>>>>
>>>>                          Thanks,     Mikek
>>>
>>> A bandwidth ratio of only three should be dead-easy,
>>> but the 20 mOhm impedance may spell trouble.
>>> The single-turn winding should be fat and compact.
>>> A single nH of stray inductance (!) or ten mOhms of resistance would
>>> ruin performance. I think I would implement it as several single-turn
>>> windings in parallel, distributed around a toroid. What will you
>>> connect to the 20mOhm side?
>>
>>   A 20mOhm resistor.
>>    I'm replacing a tube osc, I'm not able to follow the coax back to the
>> tube output on the schematic, so I don't even have a start to figure out
>> the tube output impedance. I'm starting to think it is not low.
>>   But it is able to drive 1 amp through the 0.02 ohm resistor to develop
>> 20mv.
>>
>>
>>
>>> Why would you need low A_l? The usual rule of having the reactance of
>>> one winding four times the terminal impedance is only a minimum. There
>>> is no harm in going higher. There would be if you did it by using more
>>> turns though.
>>>
>>>
>> My calculations tell me that with an AsubL of 75 it take 29 turns.
>> This still doesn't get my a 50 to 1 turn ratio.
>> If I use a core with an AsubL of 2340, I only need 5 turns, with that I
>> can't get a 50 to 1 turns ratio.
>>
>>> Use a toroid. Gapped cores are for energy storage,
>>> not for transformers.
>>>
>>> Jeroen Belleman
>>
>>   I'll restate my problem,
>> I want to substitute a more stable signal generator for the internal
>> signal generator in my Boonton 260A Q meter. The osc. in the 260A drives
>> a 0.02 ohm resistor. It actually does this through a piece of coax,
>> so I doubt it really has a 0.02 ohm output impedance. Could be I'm
>> chasing a spec. I don't need to.
>>   One advantage I have is I only want 4mv of drive across the 0.02 ohm
>> resistor, also I can adjust the signal generator output to set the
>> voltage regardless of transformer/connection losses.
>>    Thanks for the multiple single turn winding in parallel idea.
>>                              Still open to suggestions,
>>                                           Thanks, Mikek
>>
>> PS.
>> Next project is an RF detector to measure the 4mv signal, I want a
>> circuit to drive my multimeter. I suspect I'll need a preamp before the
>> detector to get any linearity. I do have a scope I can use to get a
>> useful calibration.
>
> Your calculations show you that you need a _minimum_ of 29 turns, not
> _exactly_ 29 turns.  29 is less than 50, so if you feel bound and
> determined to maintain that ratio, use 50 turns and be happy.

  Yes, I stated that in my first post.

>
> What's probably a better way (and what's probably being done in the
> meter) is to not bother matching to that resistor, but rather to build an
> amplifier that can work into a low impedance (or whatever the impedance
> is when transformed by that coax and whatever is ahead of it),

I don't know, the schematic on the Last page of this pdf. It looks to me 
like the osc tube drives the 0.02 ohms directly.
  http://www.hparchive.com/Boonton/Boonton-Manual-260A.pdf

>and just
accept whatever inefficiencies result.

> If all you want is for the thing to generally operate the way it does now
> but with a more stable oscillator, you may be best served by either
> turning the current oscillator into an amplifier stage to be driven by
> your oscillator, or injection-locking it.
>

  That's beyond my capability, I have an HP 8640B that has a frequency lock.
  Boonton produced an accessory to sub in another signal generator, it 
was designed so you could lower the frequency of operation. It was a 500 
ohm to 0.03 ohm coupling transformer.
> http://www.angelfire.com/electronic/funwithtubes/images/100_2598-B.jpg

> http://www.angelfire.com/electronic/funwithtubes/images/100_2597-B.jpg

                     Thanks for your help, Mikek

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