Hello Hari
If you are getting difficulty to obtain ferrite rods please follow the link for an alternate solution. My present Linear is with 4x811A and I am using this tuned Bifilar cathode input . SWR of 1:1 is easily obtained and the only problem is that an SWR meter is necessary at the input for tuning. Also it is tunable from 40 to 10 mtrs. Actually it was for an 813 Amp but it is doing a good job with 811A's. I am using it for the past four years without any problem.
http://www.lu1dma.com.ar/lineales/813%20Amplifier.htm
Warm regards
Jayapraksh
Jayapraksh
VU2JLH
From: Hari <harigee@yahoo.com>
To: "HamBrewers@yahoogroups.com" <HamBrewers@yahoogroups.com>
Sent: Thursday, 25 April 2013 10:50 PM
Subject: 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
73
Pramod
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