From: "Clemens Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <08B5A81DD2D14C84874DD10EEB145569@lindavideo>
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Date: Sat, 17 Oct 2015 18:48:57 +0200
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Subject: LF: RE: TX Toroid Material
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Hi Ken,

I believe two of your component values are off.
I calculate 201µH for the L next to the tubes,625pF for the shunt C and 1.1mH for the second L .
For the 201µH L I would use iron powder (Amidon #2), for the 1.1mH #43 ferrite.
Use the mini toroid calculator to find the appropiate size regarding number of turns and
allowed flux with safety margin.

73
Clemens
DL4RAJ 

 

>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org 
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Ken
>Sent: Saturday, October 17, 2015 5:41 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: LF: TX Toroid Material
>
>Dear All. I am having problems with the choice of material for 
>the output network of the 475kHz Valve TX. The network is an L 
>– C – L, ‘T’ network with an input impedance of 2100 ohms and 
>a load of 50 ohms, for this configuration the input L is 
>7.7mH, shunt capacitance is 117pf, and output L is 1.1mH. The 
>PA design using a 6146 low power or 813 high power work fine 
>when simulated using LT spice IV. When testing in the real 
>world using the 6146 there is in excess of 800v rms rf on the 
>network side of the anode coupling capacitor, but nothing 
>after the input L. I can only conclude that I using the wrong 
>type material for the toroids, I used the largest size 
>(unmarked) toroid which gave me a modest number of turns. I 
>have checked the Amidon tables and Iron Powder because of the 
>low AL values, which leaves Ferrite, which mix would you 
>recommend? The simulations give me output powers 90W for the 
>6146, and 300W for the 813. I would be grateful for any core 
>material advice .
>
> 
>
>Ken Wright.
>
>M0KHW
>
> 
>
>