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Need clarification on RF related concepts

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  Need clarification on RF related concepts dakupoto@gmail.com - 2016-10-15 23:44 -0700
    Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-16 04:37 -0500
    Re: Need clarification on RF related concepts Phil Allison <pallison49@gmail.com> - 2016-10-16 05:14 -0700
      Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-16 08:04 -0500
    Re: Need clarification on RF related concepts Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2016-10-16 17:36 +0300
      Re: Need clarification on RF related concepts dakupoto@gmail.com - 2016-10-16 23:27 -0700
        Re: Need clarification on RF related concepts amdx <nojunk@knology.net> - 2016-10-18 08:44 -0500
          Re: Need clarification on RF related concepts Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2016-10-18 11:06 -0400
          Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-07 13:38 -0500
            Re: Need clarification on RF related concepts George Herold <gherold@teachspin.com> - 2016-11-07 11:00 -0800
              Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-09 18:35 -0500
                Re: Need clarification on RF related concepts Jeff Liebermann <jeffl@cruzio.com> - 2016-11-09 19:59 -0800
                  Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-12 08:46 -0500
            Re: Need clarification on RF related concepts "nuny@bid.nes" <Alien8752@gmail.com> - 2016-11-07 11:09 -0800
              Re: Need clarification on RF related concepts "Michael A. Terrell" <mike.terrell@earthlink.net> - 2016-11-09 18:22 -0500
    Re: Need clarification on RF related concepts Tim Wescott <tim@seemywebsite.really> - 2016-10-16 14:28 -0500
    Re: Need clarification on RF related concepts rickman <gnuarm@gmail.com> - 2016-10-17 04:04 -0400
      Re: Need clarification on RF related concepts "Tim Williams" <tiwill@seventransistorlabs.com> - 2016-10-18 07:00 -0500
        Re: Need clarification on RF related concepts Jeroen Belleman <jeroen@nospam.please> - 2016-10-18 16:45 +0200
    Re: Need clarification on RF related concepts Jasen Betts <jasen@xnet.co.nz> - 2016-10-17 09:43 +0000

#431380 — Need clarification on RF related concepts

Could some electronics guru please help ?
I am a bit rusty on some RF concepts so I
request some clarifications from the gurus 
here.

By definition, a 4:1 balun has 4 times 
the impedance on the balamced side as the 
unbalanced side. For any inductor, the 
impedance is based on the reactance, which 
in turn is based on the frequency of 
operation.

So, what frequency is being considered 
here ? The reason I ask is that a balun
could be used as broadband impedance 
matching device. Thanks in advance for 
your help.


 

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#431389

On 10/16/2016 1:44 AM, dakupoto@gmail.com wrote:
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus
> here.
>
> By definition, a 4:1 balun has 4 times
> the impedance on the balamced side as the
> unbalanced side. For any inductor, the
> impedance is based on the reactance, which
> in turn is based on the frequency of
> operation.
>
> So, what frequency is being considered
> here ? The reason I ask is that a balun
> could be used as broadband impedance
> matching device. Thanks in advance for
> your help.
>

  It is my understanding that a balun is a transformer.
In order for a transformer to transform properly it needs to have
at least 4 times the inductive reactance of the impedance it is 
transforming.
Example: The primary of a 50 ohm transformer must have at least 200 ohms 
of reactance at the lowest frequency of operation. As you go lower
in frequency. at some point the reactance becomes less than 200 ohms and 
the transformer starts to become less ideal in transforming
the impedances.
So build your balun with enough impeadance to cover your lowest 
frequency and it will be broadband, (up to a point).
                                       Mikek

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#431403

aku...@gmail.com wrote:
>
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus 
> here.
> 
> By definition, a 4:1 balun has 4 times 
> the impedance on the balamced side as the 
> unbalanced side.
>

 ** Wrong - as per fucking usual. 


> For any inductor, the 
> impedance is based on the reactance, which 
> in turn is based on the frequency of 
> operation.
> 
> So, what frequency is being considered 
> here ?

** It's transformer - not an inductor. 


> The reason I ask is that a balun
> could be used as broadband impedance 
> matching device. Thanks in advance for 
> your help.
>

** Just like you can use a hammer instead of a screwdriver. 

 Works a treat, if you bang hard enough. 

 FFS,  piss of you 1/10 wit troll. 





....  Phil 

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#431411

On 10/16/2016 7:14 AM, Phil Allison wrote:
> aku...@gmail.com wrote:
>>
>> Could some electronics guru please help ?
>> I am a bit rusty on some RF concepts so I
>> request some clarifications from the gurus
>> here.

>> By definition, a 4:1 balun has 4 times
>> the impedance on the balamced side as the
>> unbalanced side.

>  ** Wrong - as per fucking usual.

>> For any inductor, the
>> impedance is based on the reactance, which
>> in turn is based on the frequency of
>> operation.
>>
>> So, what frequency is being considered
>> here ?

> ** It's transformer - not an inductor.

>> The reason I ask is that a balun
>> could be used as broadband impedance
>> matching device. Thanks in advance for
>> your help.

> ** Just like you can use a hammer instead of a screwdriver.
>  Works a treat, if you bang hard enough.
>
>  FFS,  piss of you 1/10 wit troll.
> ....  Phil

  Well that does seem very helpful,
one of those days* Phil?

                       Mikek

* a day when you skipped your meds.

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#431418

On 16.10.16 09:44, dakupoto@gmail.com wrote:
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus
> here.
>
> By definition, a 4:1 balun has 4 times
> the impedance on the balamced side as the
> unbalanced side. For any inductor, the
> impedance is based on the reactance, which
> in turn is based on the frequency of
> operation.
>
> So, what frequency is being considered
> here ? The reason I ask is that a balun
> could be used as broadband impedance
> matching device. Thanks in advance for
> your help.

A balun is a matching element between a balanced and
an unbalanced transmission line. The 4:1 balun is
in its simplest form an auto-transformer (2 identical
windings connected in series). The center tap is connected
to the unbalanced side ground, one of the ends is
connected to both the unbalanced non-grounded wire and
one of the balanced wires. The remaining end of the transformer
is connected to the remaining balanced line wire.

There can be an impedance transformation of 4:1 using
a similar transformer, but connecting the center tap to
the unbalanced non-grounded line and connecting the
common end of the transformer to ground wires of both
low-impedance and high-impedance line. The non-grounded
high-impedance line it taken from the top end of the
auto-transformer.

A similar effect can be achieved using transmission lines.
If we have a feed of impedance Z0, we can connect it to
a pair of lines of impedance 2*Z0 in parallel. If the
other ends of the lines are connected in series, there
will be a connection of impedance 4*Z0, but there is
a requirement to prevent current flow outside the transmission
lines, to prevent part of the circuit being short-circuited.
This can be achieved by coiling the lines on a suitable magnetic
core, creating an auto-transformer on low frequencies and
a transmission-line transformer on high frequencies.

Google gave pretty good responses to 'trnasmission-line transformer'.

-- 

-TV

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#431507

On Sunday, October 16, 2016 at 10:36:17 AM UTC-4, Tauno Voipio wrote:
> On 16.10.16 09:44, dakupoto@gmail.com wrote:
> > Could some electronics guru please help ?
> > I am a bit rusty on some RF concepts so I
> > request some clarifications from the gurus
> > here.
> >
> > By definition, a 4:1 balun has 4 times
> > the impedance on the balamced side as the
> > unbalanced side. For any inductor, the
> > impedance is based on the reactance, which
> > in turn is based on the frequency of
> > operation.
> >
> > So, what frequency is being considered
> > here ? The reason I ask is that a balun
> > could be used as broadband impedance
> > matching device. Thanks in advance for
> > your help.
> 
> A balun is a matching element between a balanced and
> an unbalanced transmission line. The 4:1 balun is
> in its simplest form an auto-transformer (2 identical
> windings connected in series). The center tap is connected
> to the unbalanced side ground, one of the ends is
> connected to both the unbalanced non-grounded wire and
> one of the balanced wires. The remaining end of the transformer
> is connected to the remaining balanced line wire.
> 
> There can be an impedance transformation of 4:1 using
> a similar transformer, but connecting the center tap to
> the unbalanced non-grounded line and connecting the
> common end of the transformer to ground wires of both
> low-impedance and high-impedance line. The non-grounded
> high-impedance line it taken from the top end of the
> auto-transformer.
> 
> A similar effect can be achieved using transmission lines.
> If we have a feed of impedance Z0, we can connect it to
> a pair of lines of impedance 2*Z0 in parallel. If the
> other ends of the lines are connected in series, there
> will be a connection of impedance 4*Z0, but there is
> a requirement to prevent current flow outside the transmission
> lines, to prevent part of the circuit being short-circuited.
> This can be achieved by coiling the lines on a suitable magnetic
> core, creating an auto-transformer on low frequencies and
> a transmission-line transformer on high frequencies.
> 
> Google gave pretty good responses to 'trnasmission-line transformer'.
> 
> -- 
> 
> -TV

Thanks to each of you for the insightful comments and 
jogging my memory. I am sorry I must have posted on the 
day when Phil's constipation was at its worst.

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#431637

On 10/17/2016 1:27 AM, dakupoto@gmail.com wrote:
> On Sunday, October 16, 2016 at 10:36:17 AM UTC-4, Tauno Voipio wrote:
>> On 16.10.16 09:44, dakupoto@gmail.com wrote:
>>> Could some electronics guru please help ?
>>> I am a bit rusty on some RF concepts so I
>>> request some clarifications from the gurus
>>> here.
>>>
>>> By definition, a 4:1 balun has 4 times
>>> the impedance on the balamced side as the
>>> unbalanced side. For any inductor, the
>>> impedance is based on the reactance, which
>>> in turn is based on the frequency of
>>> operation.
>>>
>>> So, what frequency is being considered
>>> here ? The reason I ask is that a balun
>>> could be used as broadband impedance
>>> matching device. Thanks in advance for
>>> your help.
>>
>> A balun is a matching element between a balanced and
>> an unbalanced transmission line. The 4:1 balun is
>> in its simplest form an auto-transformer (2 identical
>> windings connected in series). The center tap is connected
>> to the unbalanced side ground, one of the ends is
>> connected to both the unbalanced non-grounded wire and
>> one of the balanced wires. The remaining end of the transformer
>> is connected to the remaining balanced line wire.
>>
>> There can be an impedance transformation of 4:1 using
>> a similar transformer, but connecting the center tap to
>> the unbalanced non-grounded line and connecting the
>> common end of the transformer to ground wires of both
>> low-impedance and high-impedance line. The non-grounded
>> high-impedance line it taken from the top end of the
>> auto-transformer.
>>
>> A similar effect can be achieved using transmission lines.
>> If we have a feed of impedance Z0, we can connect it to
>> a pair of lines of impedance 2*Z0 in parallel. If the
>> other ends of the lines are connected in series, there
>> will be a connection of impedance 4*Z0, but there is
>> a requirement to prevent current flow outside the transmission
>> lines, to prevent part of the circuit being short-circuited.
>> This can be achieved by coiling the lines on a suitable magnetic
>> core, creating an auto-transformer on low frequencies and
>> a transmission-line transformer on high frequencies.
>>
>> Google gave pretty good responses to 'trnasmission-line transformer'.
>>
>> --
>>
>> -TV
>
> Thanks to each of you for the insightful comments and
> jogging my memory. I am sorry I must have posted on the
> day when Phil's constipation was at its worst.
>
  BTW, if you want a book that covers Baluns, Ununs and Transmision Line 
transformers with dozens of built examples including frequency response 
and loss curves, I recommend, 'Transmision Line transformers' by Jerry 
Sevick. Also includes many different ratio transformers.
                                               Mikek

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#431644

On 10/18/2016 09:44 AM, amdx wrote:

>> 
> BTW, if you want a book that covers Baluns, Ununs and Transmision
> Line transformers with dozens of built examples including frequency
> response and loss curves, I recommend, 'Transmision Line
> transformers' by Jerry Sevick. Also includes many different ratio
> transformers. Mikek

+1.  Great book.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

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#434163

amdx wrote:
>
>   BTW, if you want a book that covers Baluns, Ununs and Transmision Line
> transformers with dozens of built examples including frequency response
> and loss curves, I recommend, 'Transmision Line transformers' by Jerry
> Sevick. Also includes many different ratio transformers.


<https://ia802709.us.archive.org/6/items/fe_Transmission_Line_Transformers/Transmission_Line_Transformers.pdf>

-- 
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

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#434166

On Monday, November 7, 2016 at 1:38:10 PM UTC-5, Michael Terrell wrote:
> amdx wrote:
> >
> >   BTW, if you want a book that covers Baluns, Ununs and Transmision Line
> > transformers with dozens of built examples including frequency response
> > and loss curves, I recommend, 'Transmision Line transformers' by Jerry
> > Sevick. Also includes many different ratio transformers.
> 
> 
> <https://ia802709.us.archive.org/6/items/fe_Transmission_Line_Transformers/Transmission_Line_Transformers.pdf>
> 
Ahh.. thanks.  I found this from Amidon. 
http://www.introni.it/pdf/Amidon%20-%20Transmission%20Line%20Transformers%20Handbook.pdf

(rather large.)  

I think I'll ask Santa for one of those book reader things.  

George H.   
> -- 
> Never piss off an Engineer!
> 
> They don't get mad.
> 
> They don't get even.
> 
> They go for over unity! ;-)

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#434555

George Herold wrote:
> On Monday, November 7, 2016 at 1:38:10 PM UTC-5, Michael Terrell wrote:
>> amdx wrote:
>>>
>>>    BTW, if you want a book that covers Baluns, Ununs and Transmision Line
>>> transformers with dozens of built examples including frequency response
>>> and loss curves, I recommend, 'Transmision Line transformers' by Jerry
>>> Sevick. Also includes many different ratio transformers.
>>
>>
>> <https://ia802709.us.archive.org/6/items/fe_Transmission_Line_Transformers/Transmission_Line_Transformers.pdf>
>>
> Ahh.. thanks.  I found this from Amidon.
> http://www.introni.it/pdf/Amidon%20-%20Transmission%20Line%20Transformers%20Handbook.pdf
>
> (rather large.)
>
> I think I'll ask Santa for one of those book reader things.


    You're welcome.


    I bought an Irulu X10, 10" tablet w/octal processor 
(UltraOcta-A83)for $100 a year ago for e-books. it has 16 GB of flash, 
and Bluetooth. It runs Android 4.4.4.

    This looks like it's the current version:

    http://www.ebay.com/itm/351895892136

(iRULU-X2-Plus-10-1-Google-Android-5-1-Lollipop-Tablet-PC-Octa-Core-16GB-BT-4-0-)
-- 
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

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#434627

On Wed, 9 Nov 2016 18:35:13 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

>    I bought an Irulu X10, 10" tablet w/octal processor 
>(UltraOcta-A83)for $100 a year ago for e-books. it has 16 GB of flash, 
>and Bluetooth. It runs Android 4.4.4.
>    This looks like it's the current version:
>    http://www.ebay.com/itm/351895892136
>(iRULU-X2-Plus-10-1-Google-Android-5-1-Lollipop-Tablet-PC-Octa-Core-16GB-BT-4-0-)

The description says Android 5.1.  Good price and nice CPU, but I'm
concerned that 1GB working RAM is not enough for Android 5.1.  I have
several lesser phones and tablets floating around the office with 1GB
RAM.  They tend to be rather slow and jerky.  My collection is the
result of customer upgrades to tablets with 2GB RAM.  Does the 8 core
CPU compensate adequately for the lack of RAM or is it slow and jerky?

Also, the 1024x600 TFT screen is rather coarse, but probably adequate
for ebooks, PDF, and document reading.  The low res screen is probably
why the price is so low.  A higher resolution screen would be better,
but also much more expensive.

My current favorite and what I use is a Google Nexus 7 2013 (2nd
generation) tablet.  About $130-$175 used on eBay:
<http://www.ebay.com/itm/Google-Nexus-7-Android-Tablet-2013-UDC00234-/142173916521>
1920x1200 IPS (not TFT) screen and 2GB RAM with Android 6.0.  Make
sure you get a 2amp, not 1amp charger.

Incidentally, in anticipation of Android and application bloat, I
bought the 32GB internal storage version instead of the 16GB version.
I have not regretted the decision.  My 8GB devices are currently a
constant battle to clear out storage, with my 16GB devices rapidly
approaching where they will have the same problem.  The Google Nexus 7
tablet does NOT have a Micro-USB slot and requires a USB-OTG adapter
to read an external flash drive.  This has turned out to be a rather
clumsy way to expanding storage.  For my collection of eBooks and
PDF's, it's not a problem, but I also like to view movies, which
average 500MB/each and which rapidly deplete available storage.



-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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#435073

Jeff Liebermann wrote:
> On Wed, 9 Nov 2016 18:35:13 -0500, "Michael A. Terrell"
> <mike.terrell@earthlink.net> wrote:
>
>>     I bought an Irulu X10, 10" tablet w/octal processor
>> (UltraOcta-A83)for $100 a year ago for e-books. it has 16 GB of flash,
>> and Bluetooth. It runs Android 4.4.4.
>>     This looks like it's the current version:
>>     http://www.ebay.com/itm/351895892136
>> (iRULU-X2-Plus-10-1-Google-Android-5-1-Lollipop-Tablet-PC-Octa-Core-16GB-BT-4-0-)
>
> The description says Android 5.1.  Good price and nice CPU, but I'm
> concerned that 1GB working RAM is not enough for Android 5.1.  I have
> several lesser phones and tablets floating around the office with 1GB
> RAM.  They tend to be rather slow and jerky.  My collection is the
> result of customer upgrades to tablets with 2GB RAM.  Does the 8 core
> CPU compensate adequately for the lack of RAM or is it slow and jerky?
>
> Also, the 1024x600 TFT screen is rather coarse, but probably adequate
> for ebooks, PDF, and document reading.  The low res screen is probably
> why the price is so low.  A higher resolution screen would be better,
> but also much more expensive.
>
> My current favorite and what I use is a Google Nexus 7 2013 (2nd
> generation) tablet.  About $130-$175 used on eBay:
> <http://www.ebay.com/itm/Google-Nexus-7-Android-Tablet-2013-UDC00234-/142173916521>
> 1920x1200 IPS (not TFT) screen and 2GB RAM with Android 6.0.  Make
> sure you get a 2amp, not 1amp charger.
>
> Incidentally, in anticipation of Android and application bloat, I
> bought the 32GB internal storage version instead of the 16GB version.
> I have not regretted the decision.  My 8GB devices are currently a
> constant battle to clear out storage, with my 16GB devices rapidly
> approaching where they will have the same problem.  The Google Nexus 7
> tablet does NOT have a Micro-USB slot and requires a USB-OTG adapter
> to read an external flash drive.  This has turned out to be a rather
> clumsy way to expanding storage.  For my collection of eBooks and
> PDF's, it's not a problem, but I also like to view movies, which
> average 500MB/each and which rapidly deplete available storage.


I have used it to watch TV for hours at a time, with no problems. It 
sits on a stand, on top of a desktop computer, and under one of my 24" 
monitors so I can look over the top to use the computer, or down a few 
inches to see the tablet. I have a 32 GB micro SD card in it, full of 
old science fiction books.


    I bought mine in August of last year. It replaced a similar quad 
core that I bought in 2013. It was Kocaso M9100 9", and it only has 8GB 
of flash with 1 GB of RAM. It would freeze on video, quite often, so I 
only use it to check Email, or to use with the Magic Jack app, over my 
wireless router.


-- 
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

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#434168

On Monday, November 7, 2016 at 10:38:10 AM UTC-8, Michael Terrell wrote:
> amdx wrote:
> >
> >   BTW, if you want a book that covers Baluns, Ununs and Transmision Line
> > transformers with dozens of built examples including frequency response
> > and loss curves, I recommend, 'Transmision Line transformers' by Jerry
> > Sevick. Also includes many different ratio transformers.
> 
> 
> <https://ia802709.us.archive.org/6/items/fe_Transmission_Line_Transformers/Transmission_Line_Transformers.pdf>

  I've been looking for that for a long time, since I lost a lot of hardcopies of ARRL stuff during a move. Thanks.


  Mark L. Fergerson

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#434547

nuny@bid.nes wrote:
> On Monday, November 7, 2016 at 10:38:10 AM UTC-8, Michael Terrell wrote:
>> amdx wrote:
>>>
>>>    BTW, if you want a book that covers Baluns, Ununs and Transmision Line
>>> transformers with dozens of built examples including frequency response
>>> and loss curves, I recommend, 'Transmision Line transformers' by Jerry
>>> Sevick. Also includes many different ratio transformers.
>>
>>
>> <https://ia802709.us.archive.org/6/items/fe_Transmission_Line_Transformers/Transmission_Line_Transformers.pdf>
>
>    I've been looking for that for a long time, since I lost a lot of hardcopies of ARRL stuff during a move. Thanks.


    You're welcome.


-- 
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

[toc] | [prev] | [next] | [standalone]

#431455

On Sat, 15 Oct 2016 23:44:16 -0700, dakupoto wrote:

> Could some electronics guru please help ? I am a bit rusty on some RF
> concepts so I request some clarifications from the gurus here.
> 
> By definition, a 4:1 balun has 4 times the impedance on the balamced
> side as the unbalanced side. For any inductor, the impedance is based on
> the reactance, which in turn is based on the frequency of operation.
> 
> So, what frequency is being considered here ? The reason I ask is that a
> balun could be used as broadband impedance matching device. Thanks in
> advance for your help.

As mentioned, it's a transformer.  If it's in it's normal operating band 
of frequencies, then the leakage inductance of the transformer is 
negligible, and what the driver "sees" is largely 4x the impedance of the 
load.

Note, too, that "negligible" covers a much wider impedance variation than 
most other sub-disciplines can stand, unless you're trying to make a 
power combiner or some such.

-- 
www.wescottdesign.com

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#431513

On 10/16/2016 2:44 AM, dakupoto@gmail.com wrote:
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus
> here.
>
> By definition, a 4:1 balun has 4 times
> the impedance on the balamced side as the
> unbalanced side. For any inductor, the
> impedance is based on the reactance, which
> in turn is based on the frequency of
> operation.
>
> So, what frequency is being considered
> here ? The reason I ask is that a balun
> could be used as broadband impedance
> matching device. Thanks in advance for
> your help.

The impedance of a transformer is not the inductive reactance of the 
coils in the transformer.  A transformer reflects the circuit connected 
to the secondary to the primary according to the turns ratio.  The 
voltage and current scales by the turns ratio and the impedance scales 
by the turns ratio squared.

-- 

Rick C

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#431627

"rickman" <gnuarm@gmail.com> wrote in message 
news:nu20lk$8d2$1@dont-email.me...
> The impedance of a transformer is not the inductive reactance of the coils 
> in the transformer.  A transformer reflects the circuit connected to the 
> secondary to the primary according to the turns ratio.  The voltage and 
> current scales by the turns ratio and the impedance scales by the turns 
> ratio squared.

Of an ideal transformer, yes, but those aren't made with coils!

All real transformers are transmission line transformers, and obey impedance 
matching rules, whether you like it or not.  Some are even constructed with 
transmission line theory in mind, and attain stupendous bandwidths as a 
result.  The best part is they're so easy to design.

A conventional (lumped equivalent) transformer cannot do flat bandwidth out 
beyond, say, 90 degrees phase shift.  An ideal TLTF (again not physical, but 
a real one can get much closer) keeps on working, despite thousands of 
degrees phase shift!  :-D

Tim

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

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#431641

On 2016-10-18 14:00, Tim Williams wrote:
> "rickman" <gnuarm@gmail.com> wrote in message
> news:nu20lk$8d2$1@dont-email.me...
>> The impedance of a transformer is not the inductive reactance of the
>> coils in the transformer.  A transformer reflects the circuit
>> connected to the secondary to the primary according to the turns
>> ratio.  The voltage and current scales by the turns ratio and the
>> impedance scales by the turns ratio squared.
>
> Of an ideal transformer, yes, but those aren't made with coils!
>
> All real transformers are transmission line transformers, and obey
> impedance matching rules, whether you like it or not.  Some are even
> constructed with transmission line theory in mind, and attain stupendous
> bandwidths as a result.[...]

I'm always on the look-out for stupendous-bandwidth transformers.
How wide is that? I'm aware of Sevick's work: Roughly 3 decades
of bandwidth. I want more!

I've managed to make inverting transformers, 1:4 transformers
and hybrids with 5 decades of bandwidth. These are made of
bits of straight UT-47 coax strung with Vacuumschmelze's tiny
amorphous tape-wound ISDN transformer toroid cores. Amazing
things, these little cores, though not without quirks.

I'd love to find a way to make similar performance 1:2
transformers, but my attempts have been disappointing up to
present. The limiting factors are the unwanted capacitance to
coax screens and the residual inductance of junctions. The
end of the manufacture of my favourite Vacuumschmelze
transformer cores has set me back by at least an octave, alas.
I now wish I'd bought more of them...

Jeroen Belleman

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#431568

On 2016-10-16, dakupoto@gmail.com <dakupoto@gmail.com> wrote:
> Could some electronics guru please help ?
> I am a bit rusty on some RF concepts so I
> request some clarifications from the gurus 
> here.
>
> By definition, a 4:1 balun has 4 times 
> the impedance on the balamced side as the 
> unbalanced side. For any inductor, the 
> impedance is based on the reactance, which 
> in turn is based on the frequency of 
> operation.
>
> So, what frequency is being considered 
> here ? The reason I ask is that a balun
> could be used as broadband impedance 
> matching device. Thanks in advance for 
> your help.

A balun is a transformer, a 4:1 balun is a 2:1 ratio transformer.

(this suprising relation can be derived from P=I squared R)

Useful frequency depends on the design of the transformer. 4:1 
baluns good* for 45 to 900 MHZ operations were common in the days of
analogue broadcast television.

(*) good-enough anyway.

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

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