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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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#433670

On 3.11.16 19:15, amdx wrote:

> 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


You are not reading the schematic correctly. There is a transformer
formed by the tuned circuit in the coil turret and its link coil.

Besides, there is the impedance of the thermo-cross RF current
meter on the way, as well.

A transformer in the cable will only worsen your results.

-- 

-TV

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#433682

On Thursday, November 3, 2016 at 1:37:50 PM UTC-4, Tauno Voipio wrote:
> On 3.11.16 19:15, amdx wrote:
> 
> > 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
> 
> 
> You are not reading the schematic correctly. There is a transformer
> formed by the tuned circuit in the coil turret and its link coil.
> 
> Besides, there is the impedance of the thermo-cross RF current
> meter on the way, as well.
> 
> A transformer in the cable will only worsen your results.
> 
> -- 
> 
> -TV

right, I don't think the OP needs a 0.02 output Z,  

 he simply needs to be able to  drive some signal into 0.02 Ohms.

m

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#433695

On 11/3/2016 12:37 PM, Tauno Voipio wrote:
> On 3.11.16 19:15, amdx wrote:
>
>> 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
>
>
> You are not reading the schematic correctly. There is a transformer
> formed by the tuned circuit in the coil turret and its link coil.
>
> Besides, there is the impedance of the thermo-cross RF current
> meter on the way, as well.

  Thermo-cross? Your looking at the thermocouple?
It heats and the voltage developed drives the 'Multiply Q By' meter.
My ohmmeter reads .1 ohm when I measure just the 0.02 ohm resistor or 
the series thermocouple and 0.02 ohm resistor. So the thermocouple has 
very low resistance.

>
> A transformer in the cable will only worsen your results.
>

  I see the coil (winding) on pin 1 and 2 of the turret.
  I don't see what it links to.
Can you point out the other winding that makes a transformer?
                        Thanks,  Mikek

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#433700

On 11/3/2016 12:37 PM, Tauno Voipio wrote:
> On 3.11.16 19:15, amdx wrote:
>
>> 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
>
>
> You are not reading the schematic correctly. There is a transformer
> formed by the tuned circuit in the coil turret and its link coil.
>

  I'm can not disputing that;
  I see the B+ (342V) connected to R121 (220 ohm) and going to the 
unmarked variable inductor, then to pin 4 and the anode of the tube.
But I don't know how you know the are magnetically coupled?
It seems to make sense, I just would never have picked that up.

                                   Mikek


> Besides, there is the impedance of the thermo-cross RF current
> meter on the way, as well.
>
> A transformer in the cable will only worsen your results.
>

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#433710

On Thu, 03 Nov 2016 13:31:03 -0500, amdx wrote:

> On 11/3/2016 12:37 PM, Tauno Voipio wrote:
>> On 3.11.16 19:15, amdx wrote:
>>
>>> 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
>>
>>
>> You are not reading the schematic correctly. There is a transformer
>> formed by the tuned circuit in the coil turret and its link coil.
>>
>>
>   I'm can not disputing that;
>   I see the B+ (342V) connected to R121 (220 ohm) and going to the
> unmarked variable inductor, then to pin 4 and the anode of the tube.
> But I don't know how you know the are magnetically coupled?
> It seems to make sense, I just would never have picked that up.

It is magnetically coupled because (A) that's the only way it'd work, and 
(B), it's toobs, and that's how toob radio stuff works.

-- 

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

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

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#433712

On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:

> On 3.11.16 19:15, amdx wrote:
> 
>> 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
> 
> 
> You are not reading the schematic correctly. There is a transformer
> formed by the tuned circuit in the coil turret and its link coil.
> 
> Besides, there is the impedance of the thermo-cross RF current meter on
> the way, as well.

Oh lordy, I saw that days ago and didn't catch it.

Andy: the DC resistance of that thermocouple unit is going to be pretty 
close to the RF resistance, and I'll bet it's around 50 ohms -- or at 
least a hell of a lot closer than 20m-ohms.

-- 

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

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

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#433733

On 11/3/2016 2:39 PM, Tim Wescott wrote:
> On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
>
>> On 3.11.16 19:15, amdx wrote:
>>
>>> 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
>>
>>
>> You are not reading the schematic correctly. There is a transformer
>> formed by the tuned circuit in the coil turret and its link coil.
>>
>> Besides, there is the impedance of the thermo-cross RF current meter on
>> the way, as well.
>
> Oh lordy, I saw that days ago and didn't catch it.
>
> Andy: the DC resistance of that thermocouple unit is going to be pretty
> close to the RF resistance, and I'll bet it's around 50 ohms -- or at
> least a hell of a lot closer than 20m-ohms.
>

  No it's very low ohm.

My ohmmeter reads .1 ohm when I measure just the 0.02 ohm resistor or 
when I measure the thermocouple and 0.02 ohm resistor in series. So the 
thermocouple has very low resistance.

                             Mikek

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#433764

On Thursday, November 3, 2016 at 2:52:49 PM UTC-7, amdx wrote:
> On 11/3/2016 2:39 PM, Tim Wescott wrote:
> > On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
> >
> >> On 3.11.16 19:15, amdx wrote:
> >>
> >>> 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.
> 
>   No it's very low ohm.
> 
> My ohmmeter reads .1 ohm when I measure just the 0.02 ohm resistor or 
> when I measure the thermocouple and 0.02 ohm resistor in series. So the 
> thermocouple has very low resistance.

Er... but this is about something in the 1.9 MHz range, so there's a bit of
a problem in using a DC measurement.   Skin depth is about 0.05 millimeters
in copper at that frequency.   1mm wire, 100 mm long, is 12 milliohms at 1.9 MHz,
and only 2 miliohms at DC.
<http://chemandy.com/calculators/round-wire-ac-resistance-calculator.htm>

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#433825

On 11/3/2016 2:39 PM, Tim Wescott wrote:
> On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
>
>> On 3.11.16 19:15, amdx wrote:
>>
>>> 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
>>
>>
>> You are not reading the schematic correctly. There is a transformer
>> formed by the tuned circuit in the coil turret and its link coil.
>>
>> Besides, there is the impedance of the thermo-cross RF current meter on
>> the way, as well.
>
> Oh lordy, I saw that days ago and didn't catch it.
>
> Andy: the DC resistance of that thermocouple unit is going to be pretty
> close to the RF resistance, and I'll bet it's around 50 ohms -- or at
> least a hell of a lot closer than 20m-ohms.
>

  I did a quick crude experiment this morning before work.
I set my 50 ohm sig gen to 400mvpp, I then connected it to the
input of the 260A (thermocouple input).
  The the sig gen voltage dropped to 20mvpp, from this I get an input
impedance of 2.5 ohms for the thermocouple input.
   Maybe time for a second transformer.

                                   Mikek

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#433834

On 4.11.16 13:26, amdx wrote:
> On 11/3/2016 2:39 PM, Tim Wescott wrote:
>> On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
>>
>>> On 3.11.16 19:15, amdx wrote:
>>>
>>>> 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
>>>
>>>
>>> You are not reading the schematic correctly. There is a transformer
>>> formed by the tuned circuit in the coil turret and its link coil.
>>>
>>> Besides, there is the impedance of the thermo-cross RF current meter on
>>> the way, as well.
>>
>> Oh lordy, I saw that days ago and didn't catch it.
>>
>> Andy: the DC resistance of that thermocouple unit is going to be pretty
>> close to the RF resistance, and I'll bet it's around 50 ohms -- or at
>> least a hell of a lot closer than 20m-ohms.
>>
>
>  I did a quick crude experiment this morning before work.
> I set my 50 ohm sig gen to 400mvpp, I then connected it to the
> input of the 260A (thermocouple input).
>  The the sig gen voltage dropped to 20mvpp, from this I get an input
> impedance of 2.5 ohms for the thermocouple input.
>   Maybe time for a second transformer.
>
>                                   Mikek

Do not do that - you risk of burning the RF current meter and the
terminator resistor. The 5763 will put out around 10 W of RF when
properly matched.

-- 

-TV

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#433850

On 11/4/2016 8:20 AM, Tauno Voipio wrote:
> On 4.11.16 13:26, amdx wrote:
>> On 11/3/2016 2:39 PM, Tim Wescott wrote:
>>> On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
>>>
>>>> On 3.11.16 19:15, amdx wrote:
>>>>
>>>>> 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
>>>>
>>>>
>>>> You are not reading the schematic correctly. There is a transformer
>>>> formed by the tuned circuit in the coil turret and its link coil.
>>>>
>>>> Besides, there is the impedance of the thermo-cross RF current meter on
>>>> the way, as well.
>>>
>>> Oh lordy, I saw that days ago and didn't catch it.
>>>
>>> Andy: the DC resistance of that thermocouple unit is going to be pretty
>>> close to the RF resistance, and I'll bet it's around 50 ohms -- or at
>>> least a hell of a lot closer than 20m-ohms.
>>>
>>
>>  I did a quick crude experiment this morning before work.
>> I set my 50 ohm sig gen to 400mvpp, I then connected it to the
>> input of the 260A (thermocouple input).
>>  The the sig gen voltage dropped to 20mvpp, from this I get an input.
 >>  impedance of 2.5 ohms for the thermocouple input.
>>   Maybe time for a second transformer.
>>
>>                                   Mikek
>
> Do not do that - you risk of burning the RF current meter and the
> terminator resistor. The 5763 will put out around 10 W of RF when
> properly matched.
>
    Yes, I'm aware of all the cautions regarding the thermocouple.
Almost every website I read has a thermocouple warning, the only person 
that says "relax, if the thermocouple is still good your unlikely to 
burn it out," is a guy that worked at Boonton and has his inspection # 
on many units.
My sig Gen with a 50 ohm output impedance would not drive enough current 
to harm the thermocouple.
When the Multiplier is set to 1, there is 20mv across the 0.02 ohm 
resistor, that is one amp of current! About all I can get out of my
sig gen is 200ma.
   But yes, the part is unobtainable, so I use care.
Easy to monitor the voltage across the LOW connector and GRD, that
is the voltage across the 0.02 ohm resistor.
                                  Thank, Mikek

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#433893

On 4.11.16 16:33, amdx wrote:
> On 11/4/2016 8:20 AM, Tauno Voipio wrote:
>> On 4.11.16 13:26, amdx wrote:
>>> On 11/3/2016 2:39 PM, Tim Wescott wrote:
>>>> On Thu, 03 Nov 2016 19:37:44 +0200, Tauno Voipio wrote:
>>>>
>>>>> On 3.11.16 19:15, amdx wrote:
>>>>>
>>>>>> 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
>>>>>
>>>>>
>>>>> You are not reading the schematic correctly. There is a transformer
>>>>> formed by the tuned circuit in the coil turret and its link coil.
>>>>>
>>>>> Besides, there is the impedance of the thermo-cross RF current
>>>>> meter on
>>>>> the way, as well.
>>>>
>>>> Oh lordy, I saw that days ago and didn't catch it.
>>>>
>>>> Andy: the DC resistance of that thermocouple unit is going to be pretty
>>>> close to the RF resistance, and I'll bet it's around 50 ohms -- or at
>>>> least a hell of a lot closer than 20m-ohms.
>>>>
>>>
>>>  I did a quick crude experiment this morning before work.
>>> I set my 50 ohm sig gen to 400mvpp, I then connected it to the
>>> input of the 260A (thermocouple input).
>>>  The the sig gen voltage dropped to 20mvpp, from this I get an input.
>>>  impedance of 2.5 ohms for the thermocouple input.
>>>   Maybe time for a second transformer.
>>>
>>>                                   Mikek
>>
>> Do not do that - you risk of burning the RF current meter and the
>> terminator resistor. The 5763 will put out around 10 W of RF when
>> properly matched.
>>
>    Yes, I'm aware of all the cautions regarding the thermocouple.
> Almost every website I read has a thermocouple warning, the only person
> that says "relax, if the thermocouple is still good your unlikely to
> burn it out," is a guy that worked at Boonton and has his inspection #
> on many units.
> My sig Gen with a 50 ohm output impedance would not drive enough current
> to harm the thermocouple.
> When the Multiplier is set to 1, there is 20mv across the 0.02 ohm
> resistor, that is one amp of current! About all I can get out of my
> sig gen is 200ma.
>   But yes, the part is unobtainable, so I use care.
> Easy to monitor the voltage across the LOW connector and GRD, that
> is the voltage across the 0.02 ohm resistor.
>                                  Thank, Mikek


The 5763 is a transmitting tube. It was a very popular driver tube in
the tube era ham transmitters, driving usually a pair of 6146's for
about 200 W output.

-- 

-TV

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#433687

"amdx" <nojunk@knology.net> wrote in message 
news:nvfrar$295$1@dont-email.me...
> 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
>
>

The coax is driven from the winding connected to pins 1 &2 of the turret. 
That winding couples RF from the plate winding connected to pins 4 & 8. The 
coax feeds the series load of the thermocouple and the 0.02 ohm resistor.

Regards,
Tom 

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#433666

amdx wrote...
>
> What problems can I expect with a 1 turn secondary?

 It's all a matter of the core.  I made a 1:20 step-up
 transformer with a 1-turn primary.  The primary "wire"
 was a copper strip 1-inch wide.  The secondary was 20
 turns of a large litz wire, wound with mucho Kapton
 tape insulation.  The 1-turn primary voltage was 500V,
 and the secondary voltage was 10kV.  It was amazing
 to contemplate a foot of thick 1-inch-wide copper
 strip, holding off 500V eed-to-end.  Worked great!


-- 
 Thanks,
    - Win

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#433885

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.  

-- 
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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#433895

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. Measuring higher Q's does not need
(or tolerate) increased excitation to the DUT.

-- 

-TV

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#433908

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

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#434010

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

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#433957

On 11/3/2016 5:55 AM, 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
The guys who make CD Spot Welders should know about this stuff.

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