[Boatanchors] Choke Info Needed

[Carl]

----- Original Message ----- 
From: "mac" <w7qho at aol.com>
To: "Carl" <km1h at jeremy.mv.com>
Cc: "Mark K3MSB" <mark.k3msb at gmail.com>; "List Boatanchors" 
<boatanchors at mailman.qth.net>; "Kenneth D. Grimm,K4XL" <grimm at sbc.edu>
Sent: Friday, October 09, 2009 1:52 PM
Subject: Re: [Boatanchors] Choke Info Needed


>
>
>
>
> On Oct 9, 2009, at 6:59 AM, Carl wrote:
>
>> Low C was only before higher values became readily available/ affordable 
>> and pretty much confined to pre WW2.
>
> Yes, of course, but we were talking tradition......


My tradition starts in the early 50's; prior was old history.


>
>> In a modulator with a 5-25H or higher swinger input and 40+ uF  output C 
>> the ripple is not audible.
>
> Obviously.
>
>> This assumes that the driver stages are well filtered to eliminate  the 
>> GIGO effect. Minimum bleeder current is needed to keep the HV  from 
>> soaring and once the modulator tubes are on they provide the  remaining 
>> bleeder stabilzation.
>
> And all a swinging choke really does is allow the use of a higher 
> resistance, lower wattage bleeder resistor in those cases where the  load 
> current will fall below a critical value during normal operation,  CW 
> being the classic situation.


That was far from the original reason. A wirewound resistor was cheap and 
chokes were expensive.
The swinger is simply an economy version of the smoothing. Nothing mandatory 
about it except typical
ham mythology


>
>> The resultant HV variation in a Class B modulator is better than  most 
>> SSB linears.
>>
>> In an AM only RF amp many do away with the choke and use a lot of C  when 
>> a low impedance transformer is used. However when using old  high 
>> impedance iron a choke input is recommended with SS rectifiers  and 
>> mandatory with 866's. I use only SS in all the power supplies  and a mix 
>> of transformers and filter schemes.
>
> My original query to Mark was why a swinging choke? Subsequently  learned 
> he was building up a PS for an ART-13.  Swinging choke nice to  use on a 
> choke input filter if you can find one but not mandatory as  many appear 
> to believe.  I use a 10H, 300ma "smoothing" type in the PS  for my ATC.


I use a 12H that was on hand for rmy ATC followed by a stack of 220uF 
electrolytics.
Great regulation, takes up minimal space, and works well. Love to watch the 
autotune!

Carl
KM1H


>
> Dennis D. W7QHO
> Glendale, CA