Bifilar Wound Balun Transformer

On 11/3/2012 9:28 PM, Jeff Liebermann wrote:
> On Sat, 03 Nov 2012 17:15:27 -0400, rickman<gnuarm@gmail.com>  wrote:
>
>> Any pointers?
>> Rick
>
> If you're connecting to an antenna, this might be helpful:
>
> A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing
> <http://audiosystemsgroup.com/RFI-Ham.pdf>
> Quoting:
>     The primary function of most baluns, at least in our ham
>     stations, is to minimize the interaction of our antennas
>     with the transmission lines that connect them to our radios.
> There's more to baluns than just impedance matching.
>

Wow, that's a lot of reading.  Thanks.

Rick

On 11/3/2012 9:42 PM, John Larkin wrote:
> On Sat, 3 Nov 2012 20:40:37 -0500, "Tim Williams"
> <tmoranwms@charter.net>  wrote:
>
>> "John Larkin"<jjlarkin@highNOTlandTHIStechnologyPART.com>  wrote in
>> message news:ffcb985qk94e0cf265odu97o95d90sp1bh@4ax.com...
>>> We do exactly that in a bunch of products, namely use the shield as a
>>> primary winding and the inner as the fully isolated secondary of a
>>> transformer. We do 1:1 and 1:2 (voltage step up) at levels from 5
>>> volts to over 100.
>>>
>>> https://dl.dropbox.com/u/53724080/Circuits/Xfmrs.JPG
>>>
>>> This makes a transformer with very low leakage inductance, so we get
>>> sub-ns rise times into a 50 ohm load.
>>
>> Except that, as I said, the leakage is not particularly low.  One gets
>> better performance in that regard from, say, copper foil pairs (which,
>> ultimately, is still doing the same thing, but with a low impedance
>> symmetrical stripline, not 50 ohm coax).  Which is often done in power
>> circuitry.  But "very low leakage" is not what you're going for, so it's
>> best not to claim that's what you're doing.
>>
>> Tim
>
> But it works.

See, this is the sort of stuff that, if I were a potential customer, 
would turn me off to doing business with you.  Geeze, if I am talking to 
someone about what is going on in a system and they say to me, "but it 
works", I would think they didn't understand it at all.

Do you not see how your posts make you look?

Rick

On Sat, 03 Nov 2012 18:50:54 -0500, Tim Williams wrote:

> The important thing about transmission line transformers is to forget
> about using them as transformers.  Use them as transmission lines!

Anybody know how to accurately model a transmission line transformer in
Spice, taking into account core properties?

-- 
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Fred Abse a �crit :
> On Sat, 03 Nov 2012 18:50:54 -0500, Tim Williams wrote:
> 
>> The important thing about transmission line transformers is to forget
>> about using them as transformers.  Use them as transmission lines!
> 
> Anybody know how to accurately model a transmission line transformer in
> Spice, taking into account core properties?
> 

For a simple one, just as it is:
use a TLine/RLC tline and between the 2 ""shield/ref plane" connections 
you just tie the magnetizing inductance, with maybe your core model 
(losses, non linearities, hysteresis,...)


-- 
Thanks,
Fred.

On Sun, 04 Nov 2012 18:57:27 +0100, Fred Bartoli <" "> wrote:

>Fred Abse a &#4294967295;crit :
>> On Sat, 03 Nov 2012 18:50:54 -0500, Tim Williams wrote:
>> 
>>> The important thing about transmission line transformers is to forget
>>> about using them as transformers.  Use them as transmission lines!
>> 
>> Anybody know how to accurately model a transmission line transformer in
>> Spice, taking into account core properties?
>> 
>
>For a simple one, just as it is:
>use a TLine/RLC tline and between the 2 ""shield/ref plane" connections 
>you just tie the magnetizing inductance, with maybe your core model 
>(losses, non linearities, hysteresis,...)

What's interesting about the LT Spice transmission lines is that they
have no common-mode DC continuity between ends. They act as if there
is an ideal 1:1 isolation transformer in the circuit.

That sort of makes sense, since, say, the outer conductor of a coax
has its own complex impedance against the universe, and Spice elects
to not model that. Still, it can throw you if you don't know about it,
and make baluns seem to work much better than they will in real life.

So a txline can make a handy 1:1 ideal transformer. Unlike a 1:1 VCVS,
it's bidirectional and the output loads the input.



-- 

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

John Larkin a �crit :
> On Sun, 04 Nov 2012 18:57:27 +0100, Fred Bartoli <" "> wrote:
> 
>> Fred Abse a &#4294967295;crit :
>>> On Sat, 03 Nov 2012 18:50:54 -0500, Tim Williams wrote:
>>>
>>>> The important thing about transmission line transformers is to forget
>>>> about using them as transformers.  Use them as transmission lines!
>>> Anybody know how to accurately model a transmission line transformer in
>>> Spice, taking into account core properties?
>>>
>> For a simple one, just as it is:
>> use a TLine/RLC tline and between the 2 ""shield/ref plane" connections 
>> you just tie the magnetizing inductance, with maybe your core model 
>> (losses, non linearities, hysteresis,...)
> 
> What's interesting about the LT Spice transmission lines is that they
> have no common-mode DC continuity between ends. They act as if there
> is an ideal 1:1 isolation transformer in the circuit.
> 
> That sort of makes sense, since, say, the outer conductor of a coax
> has its own complex impedance against the universe, and Spice elects
> to not model that. Still, it can throw you if you don't know about it,
> and make baluns seem to work much better than they will in real life.
> 

If you want to accurately model a coax cable you need two TLines. One 
modeling the center/shield transmission line, and a second one to model 
the shield WRT to "space".

> So a txline can make a handy 1:1 ideal transformer. Unlike a 1:1 VCVS,
> it's bidirectional and the output loads the input.
> 

The "standard" perfect transformer is composed of a vcvs to transport 
voltage to the secondary and a CCCS to reflect the secondary current 
back to the primary, and a 0 voltage source to probe it.
It is much less computationally demanding than the Tline which has to 
maintain history.


-- 
Thanks,
Fred.

On 11/3/2012 10:25 PM, rickman wrote:
> On 11/3/2012 9:42 PM, John Larkin wrote:
>> On Sat, 3 Nov 2012 20:40:37 -0500, "Tim Williams"
>> <tmoranwms@charter.net>  wrote:
>>
>>> "John Larkin"<jjlarkin@highNOTlandTHIStechnologyPART.com>  wrote in
>>> message news:ffcb985qk94e0cf265odu97o95d90sp1bh@4ax.com...
>>>> We do exactly that in a bunch of products, namely use the shield as a
>>>> primary winding and the inner as the fully isolated secondary of a
>>>> transformer. We do 1:1 and 1:2 (voltage step up) at levels from 5
>>>> volts to over 100.
>>>>
>>>> https://dl.dropbox.com/u/53724080/Circuits/Xfmrs.JPG
>>>>
>>>> This makes a transformer with very low leakage inductance, so we get
>>>> sub-ns rise times into a 50 ohm load.
>>>
>>> Except that, as I said, the leakage is not particularly low.  One gets
>>> better performance in that regard from, say, copper foil pairs (which,
>>> ultimately, is still doing the same thing, but with a low impedance
>>> symmetrical stripline, not 50 ohm coax).  Which is often done in power
>>> circuitry.  But "very low leakage" is not what you're going for, so it's
>>> best not to claim that's what you're doing.
>>>
>>> Tim
>>
>> But it works.
>
> See, this is the sort of stuff that, if I were a potential customer,

Well, apparently you're not.

> would turn me off to doing business with you.

Oops! One potential customer lost! Damn, John, this will put you out of 
business.


Geeze, if I am talking to
> someone about what is going on in a system and they say to me, "but it
> works", I would think they didn't understand it at all.

Maybe the foot is on the other shoe. Maybe you didn't understand it at all.

> Do you not see how your posts make you look?
>
> Rick

And you understand how your posts look? That's curious.

On Sat, 03 Nov 2012 23:25:46 -0400, rickman <gnuarm@gmail.com> wrote:

>On 11/3/2012 9:42 PM, John Larkin wrote:
>> On Sat, 3 Nov 2012 20:40:37 -0500, "Tim Williams"
>> <tmoranwms@charter.net>  wrote:
>>
>>> "John Larkin"<jjlarkin@highNOTlandTHIStechnologyPART.com>  wrote in
>>> message news:ffcb985qk94e0cf265odu97o95d90sp1bh@4ax.com...
>>>> We do exactly that in a bunch of products, namely use the shield as a
>>>> primary winding and the inner as the fully isolated secondary of a
>>>> transformer. We do 1:1 and 1:2 (voltage step up) at levels from 5
>>>> volts to over 100.
>>>>
>>>> https://dl.dropbox.com/u/53724080/Circuits/Xfmrs.JPG
>>>>
>>>> This makes a transformer with very low leakage inductance, so we get
>>>> sub-ns rise times into a 50 ohm load.
>>>
>>> Except that, as I said, the leakage is not particularly low.  One gets
>>> better performance in that regard from, say, copper foil pairs (which,
>>> ultimately, is still doing the same thing, but with a low impedance
>>> symmetrical stripline, not 50 ohm coax).  Which is often done in power
>>> circuitry.  But "very low leakage" is not what you're going for, so it's
>>> best not to claim that's what you're doing.
>>>
>>> Tim
>>
>> But it works.
>
>See, this is the sort of stuff that, if I were a potential customer, 
>would turn me off to doing business with you.  Geeze, if I am talking to 
>someone about what is going on in a system and they say to me, "but it 
>works", I would think they didn't understand it at all.

I'm an engineer. I don't need to understand it, I only need to make it
work. If a deep theoretical understanding of transmission-line
transformers is helpful, I might use it. But if an hour of
instinct-driven experimenting works, I'll go with that. My
mosfet-transmission-line output stage, which we've used thousands of
times, took about an hour of experimenting to design.

Some of the stuff that we do is so complex that closed-form solutions
are impossible, and serious simulation would cost way too much time
and money. 

In the electronic design business, we seldom really understand what
we're doing, at the first-principles level. We usually work further up
the abstraction stack. We usually buy parts, read data sheets, and
connect them up. It's actually unusual to *make* a part. [1]

>
>Do you not see how your posts make you look?

I posted pics of actual isolating transformers made with micro-coax.
And some nice sub-ns-risetime 100 volt pulses that were pumped through
similar transformers. Why would a customer be turned off by something
that works?

A sub-ns rise time into a 50 ohm load implies equivalent leakage
inductance in the 10s of nH. 

[1] invite interesting tales of actually making components.


-- 

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

John S wrote:
> On 11/3/2012 10:25 PM, rickman wrote:
> 
>> On 11/3/2012 9:42 PM, John Larkin wrote:
>>
>>> On Sat, 3 Nov 2012 20:40:37 -0500, "Tim Williams"
>>> <tmoranwms@charter.net>  wrote:
>>>
>>>> "John Larkin"<jjlarkin@highNOTlandTHIStechnologyPART.com>  wrote in
>>>> message news:ffcb985qk94e0cf265odu97o95d90sp1bh@4ax.com...
>>>>
>>>>> We do exactly that in a bunch of products, namely use the shield as a
>>>>> primary winding and the inner as the fully isolated secondary of a
>>>>> transformer. We do 1:1 and 1:2 (voltage step up) at levels from 5
>>>>> volts to over 100.
>>>>>
>>>>> https://dl.dropbox.com/u/53724080/Circuits/Xfmrs.JPG
>>>>>
>>>>> This makes a transformer with very low leakage inductance, so we get
>>>>> sub-ns rise times into a 50 ohm load.
>>>>
>>>>
>>>> Except that, as I said, the leakage is not particularly low.  One gets
>>>> better performance in that regard from, say, copper foil pairs (which,
>>>> ultimately, is still doing the same thing, but with a low impedance
>>>> symmetrical stripline, not 50 ohm coax).  Which is often done in power
>>>> circuitry.  But "very low leakage" is not what you're going for, so 
>>>> it's
>>>> best not to claim that's what you're doing.
>>>>
>>>> Tim
>>>
>>>
>>> But it works.
>>
>>
>> See, this is the sort of stuff that, if I were a potential customer,
> 
> 
> Well, apparently you're not.
> 
>> would turn me off to doing business with you.
> 
> 
> Oops! One potential customer lost! Damn, John, this will put you out of 
> business.
> 
> 
> Geeze, if I am talking to
> 
>> someone about what is going on in a system and they say to me, "but it
>> works", I would think they didn't understand it at all.
> 
> 
> Maybe the foot is on the other shoe. Maybe you didn't understand it at all.
> 
>> Do you not see how your posts make you look?
>>
>> Rick
> 
> 
> And you understand how your posts look? That's curious.
> 
> 
Those that don't know shit, should shit elsewhere ! Get it?

  The doctor made a mistake when you were born, they disposed the best
part that came out of your mother, the afterbirth.

Jamie

John Larkin wrote:

> On Sat, 03 Nov 2012 23:25:46 -0400, rickman <gnuarm@gmail.com> wrote:
> 
> 
>>On 11/3/2012 9:42 PM, John Larkin wrote:
>>
>>>On Sat, 3 Nov 2012 20:40:37 -0500, "Tim Williams"
>>><tmoranwms@charter.net>  wrote:
>>>
>>>
>>>>"John Larkin"<jjlarkin@highNOTlandTHIStechnologyPART.com>  wrote in
>>>>message news:ffcb985qk94e0cf265odu97o95d90sp1bh@4ax.com...
>>>>
>>>>>We do exactly that in a bunch of products, namely use the shield as a
>>>>>primary winding and the inner as the fully isolated secondary of a
>>>>>transformer. We do 1:1 and 1:2 (voltage step up) at levels from 5
>>>>>volts to over 100.
>>>>>
>>>>>https://dl.dropbox.com/u/53724080/Circuits/Xfmrs.JPG
>>>>>
>>>>>This makes a transformer with very low leakage inductance, so we get
>>>>>sub-ns rise times into a 50 ohm load.
>>>>
>>>>Except that, as I said, the leakage is not particularly low.  One gets
>>>>better performance in that regard from, say, copper foil pairs (which,
>>>>ultimately, is still doing the same thing, but with a low impedance
>>>>symmetrical stripline, not 50 ohm coax).  Which is often done in power
>>>>circuitry.  But "very low leakage" is not what you're going for, so it's
>>>>best not to claim that's what you're doing.
>>>>
>>>>Tim
>>>
>>>But it works.
>>
>>See, this is the sort of stuff that, if I were a potential customer, 
>>would turn me off to doing business with you.  Geeze, if I am talking to 
>>someone about what is going on in a system and they say to me, "but it 
>>works", I would think they didn't understand it at all.
> 
> 
> I'm an engineer. I don't need to understand it, I only need to make it
> work. If a deep theoretical understanding of transmission-line
> transformers is helpful, I might use it. But if an hour of
> instinct-driven experimenting works, I'll go with that. My
> mosfet-transmission-line output stage, which we've used thousands of
> times, took about an hour of experimenting to design.
> 
> Some of the stuff that we do is so complex that closed-form solutions
> are impossible, and serious simulation would cost way too much time
> and money. 
> 
> In the electronic design business, we seldom really understand what
> we're doing, at the first-principles level. We usually work further up
> the abstraction stack. We usually buy parts, read data sheets, and
> connect them up. It's actually unusual to *make* a part. [1]
> 
> 
>>Do you not see how your posts make you look?
> 
> 
> I posted pics of actual isolating transformers made with micro-coax.
> And some nice sub-ns-risetime 100 volt pulses that were pumped through
> similar transformers. Why would a customer be turned off by something
> that works?
> 
> A sub-ns rise time into a 50 ohm load implies equivalent leakage
> inductance in the 10s of nH. 
> 
> [1] invite interesting tales of actually making components.
> 
> 
  At least you actually do something, not like a good many here that 
would like to make people think otherwise.

  I spend more time at actually experimenting with what works the best 
instead of fighting with PC software that only gets it close but not
good enough.

   I just love those that talk shit and most likely hardly even touch a
piece of equipment. When they do I am sure they're all thumbs and 
fingers with it and most likely end up getting some one else to do it 
for them and take all the credit for it.

   Those guilty of this need not to step forward, I already know who 
most of you are.

Jamie