On Mar 22, 2005, at 2:04 PM, Wade Bates wrote:
> I am also looking to make a transformer for the input of a tetrode amp
> but
> only for 160 and 80 have been doing a lot of reading but haven't quite
> figured it out. 50 to 200 ohms also. I would only be running about 50
> watts
> input. Am putting 4 4-250 in parallel. What could I use and how may
> turns?
The bifilar xfmr at:
http://www.somis.org/D_a_05.GIF
would work for 160m and 80m. If you use Mu=125 material, it would need
fewer turns. 4, 4-250As in AB1 in parallel sounds formidable if one
uses c. 4kV for the anodes and 800v for the screens.
cheers, Wade
> Any help would be
> ----- Original Message -----
> From: "R.Measures" <r@somis.org>
> To: <gdaught6@stanford.edu>
> Cc: <amps@contesting.com>
> Sent: Tuesday, March 22, 2005 12:44 PM
> Subject: Re: [Amps] 50ohm:200ohm toroidal transformer
>
>
>>
>> On Mar 22, 2005, at 9:07 AM, gdaught6@stanford.edu wrote:
>>
>>> Hi all,
>>>
>>> I'm trying to build a 50:200 ohm broadband transformer for the input
>>> of a tetrode amplifier. Sevick's book and Measures' website give
>>> instructions for such a 2.4 inch unun. Sevick says it can handle
>>> over a kW: I only need a 100W job.
>>
>> George -- I used a 2.4 inch core because it was large enough to wind
>> myself without having to hire a lepruchuan. The amount of extra money
>> spent for the 2.4" core is minimal. A caveat -- If the amplifier is
>> to
>> be used above 10MHz, a Mu=40 core is preferable because Mu=125 cores
>> begin to saturate c. 13MHz. In my experiences, sellers of ferrite
>> cores and sellers of automobiles are comparable in truthfulness.
>>
>>> The ARRL handbook says a 1.5 inch
>>> version will handle over 100W. Does anyone have a "recipe" I could
>>> follow to make such a thing? Requirements are:
>>>
>>> a) 50 Ohms to 200 Ohms
>>> b) 3-30MHz
>>> c) low loss (I don't want it heating up and self-destructing)
>>>
>>> What core material and what size should I use? What is the best
>>> place to get one (or two) of the cores? What wire and how many turns
>>> should I use?
>>>
>>> I readily confess that I'm woefully knowledge-and-understanding-
>>> deprived in this area!
>>>
>>> Thanks in advance for any help!
>>>
>>>
>>> 73,George T. Daughters, K6GT
>>>
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
>>
>> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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