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Groups > sci.electronics.design > #433850
| From | amdx <nojunk@knology.net> |
|---|---|
| Newsgroups | sci.electronics.design |
| Subject | Re: 50 ohms to 0.02 ohm transformer |
| Date | 2016-11-04 09:33 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <nvi668$hgn$1@dont-email.me> (permalink) |
| References | (4 earlier) <nvfrar$295$1@dont-email.me> <nvfske$7eb$1@dont-email.me> <iZqdnaJegPX4D4bFnZ2dnUU7-IcAAAAA@giganews.com> <nvhr7o$ahc$1@dont-email.me> <nvi1uu$kr$2@dont-email.me> |
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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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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