Thursday, April 25, 2013

Re: [HamBrewers] Re: 811 Filament choke value

 

Pramod,

   No not an SMPS iam planning to use a transformer for filament , these days getting a ferrite rod is difficult hence the idea to go for a toroid.I had look at the SMPS design for the HT but yet to make up my mind to do that ! 

73
Hari 


From: Pramod <vu2ttp@gmail.com>
To: HamBrewers@yahoogroups.com
Sent: Sunday, April 21, 2013 6:37 PM
Subject: [HamBrewers] Re: 811 Filament choke value

 
Hari,
You cannot use a ferrite torroid if the filament supply is DC as it would result in core saturation thereby rendering it useless. I have never seen a torroid used in this application, universally in almost all GG hf amps people use bifilar wound 20 to 30 turns on a 1\2 inch dia 5 inch long ferrite rod with a mu of 125. Basically this choke has to just feed dc bias to the filament while simultaneously blocking the rf excitation from getting into your filament pwr supply, really needed if you are using the SMPS there....
73
Pramod


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