Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.electronics.design > #434010

Re: 50 ohms to 0.02 ohm transformer

Show all headers | View raw

On 11/4/2016 4:46 PM, amdx wrote:
> On 11/4/2016 2:24 PM, Tauno Voipio wrote:
>> On 4.11.16 20:24, Jeff Liebermann wrote:
>>> On Thu, 3 Nov 2016 07:55:14 -0500, amdx <nojunk@knology.net> 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
>>>
>>>
>>> Are you perhaps building an AM broadcast band to power line coupler?
>>> If so, how much RF power?  If not, just ignore the following.
>>>
>>> Way back on college daze, I helped build such a contrivance for the
>>> campus AM radio station.  The problem was how to keep 60Hz AC from
>>> going back through the transformer and AM modulating the final stages.
>>> The fix was to use a ferrite toroid, which coupled the RF quite
>>> nicely, but none of the 60Hz.  As I barely recall from 46 years ago,
>>> it was an ordinary ferrite toroid core about 2" OD.  However, I don't
>>> recall the ferrite material used or number turns involved.  No need
>>> for a pot core since the transformer was inside an aluminum box.  I'll
>>> see if I can find some details (time permitting).  Google for "carrier
>>> current AM transmitter"
>>>
>>> Also, do you really need broadband for your unspecified application?
>>> Going from 0.5MHz to 1.7MHz without tuning is nice, but if your
>>> transmitter doesn't change frequency, an LC tuned arrangement (tapped
>>> coil or two capacitors) might be easier than a toroid.
>>
>>
>> It seems that the OP is hacking an old Boonton Q meter, attempting
>> to extend its measurement range, without the proper theoretical
>> background to do it properly.
>
> Pretty true, I'm a fish monger by trade..
> The transformer was an attempt to use a different more stable osc.
> Abandoning that for now, in favor of getting my Q measurements done.
>
>> Measuring higher Q's does not need
>> (or tolerate) increased excitation to the DUT.
>
>  You're correct again, in "does not need increased excitation"
>
>  but I'm not increasing excitation, I'm lowering it.
>
> I'm lowering the drive voltage from 20mv to 4 mv this changes
> the multiplier of the Q meter from 1 to 5. With that I can measure
> up to a Q of 1250.
>
>  If you would like to be helpful, I'd like to measure the low mv RF
> signal. I could use a design for a diode detector to measure down to
> 3.33mv with the output driving a DMM. I would like a low capacitance
> input, probably a fet input MPF102/2N3819 which I have, and an amp using
> 2N2222, 2N2907, 2n3904, or 2n3906 which I have. I also have 2n4401/4403.
> 1n34A will be the diode I'd have. Frequency range 500kHz to 1700kHz. I
> want it to run from 9V. FWIW, the source impedance is 0.02 ohms.
>  I understand it will be non linear, that is fine, I can build up a
> cheat sheet of the 4 voltage setting I have interest in, 3.33mv, 4mv,
> 5mv and 6.66mv. I can use my scope to get enough accuracy to make the
> cheat sheet.
>
>                         Thanks,  Mikek
>
>
>
   I have pretty well solved what was a ground loop problem putting the 
60Hz signal on my osc. So the transformer is not so important now. Maybe 
later, because I would still like a more stable osc.

   Solving the ground loop allows me to use a scope or RF meter to 
monitor injection voltage, but the scope allows turning drive to zero, 
the RF meter still only goes to 2mv.

                                  Mikek

Back to sci.electronics.design | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

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

csiph-web