This is 29 turns each of 10 awg enameled wire bifilar over a 0.5" x 7.5"
rod. It is in a well-worn box labeled "B&W FC-25A" but I have no idea if it
is the th actual B&W product.
Steve KK7UV
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "Roger" <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Tuesday, December 23, 2008 7:45 AM
Subject: Re: [Amps] [rfamplifiers] which cathode choke?
> That sounds like the old Radiokit 30A choke kit. It worked well down to
> 160M with a single 4-1000A
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Roger" <sub1@rogerhalstead.com>
> Cc: <amps@contesting.com>
> Sent: Tuesday, December 23, 2008 12:15 AM
> Subject: Re: [Amps] [rfamplifiers] which cathode choke?
>
>
>>
>>
>> jeremy-ge wrote:
>>> Id lean to the B&W, it gives you almost 500 Ohms Xl at 160 which is
>>> OK.
>>> Bypass the filament transformer end with .05 to .1 uF discaps. Ive no
>>> idea what the MFJ's intended use is.
>>>
>> "Back in the old day", I wound a number of them on ferrite rods. I
>> only
>> remember the approximation of size but it seems as if the specs were
>> in
>> one of the handbooks. The rod was between 1/2 and 5/8" in diameter
>> and
>> about 6" long. The winding was close spaced, bifilar wound using #10
>> enameled wire. One would handle a pair of 3-500's or 8877. I had a
>> bunch
>> of them but they and a lot of other stuff went when I did the first
>> thorough clean out of "stuff I'll probably never use". I wish I had
>> all
>> that *stuff* back.
>>
>> At any rate, the chokes were easy to wind, worked well, cost little,
>> and looked good. I say they worked well. They was 80 through 10. I
>> never tried one on 160 and I don't remember the impedance.
>>> The homebrew will work also but you will have to keep an eye on the
>>> voltage drop.
>>>
>> I used one of the above on a pair of 813's with the voltage remaining
>> well with in spec. Too bad it was so long ago that I don't remember
>> any
>> specifics.
>>
>> 73
>>
>> Roger (K8RI)
>>> Carl
>>> KM1H
>>>
>>> ----- Original Message -----
>>> From: "Steve Flood" <kk7uv@bresnan.net>
>>> To: <rfamplifiers@yahoogroups.com>; <amps@contesting.com>
>>> Sent: Sunday, December 21, 2008 8:19 AM
>>> Subject: [rfamplifiers] which cathode choke?
>>>
>>>
>>> I have three different bifilar wound ferrite rod chokes.
>>>
>>> A homebrew choke measuring 127uH
>>> A B&W FC-25A measuring 44uH.
>>> An Ameritron/MFJ #10-15115-1 measuring 19uH.
>>> The measurements were taken on one winding with an Elenco LCR meter.
>>>
>>> Which one would best for grounded-grid 813's operating 160m thru 20m?
>>>
>>> Thanks, Steve KK7UV
>>>
>>> _______________________________________________
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>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
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