Date: Sat, 17 Oct 2015 18:50:05 +0000
Message-ID: <20151017185005.Horde.St3c5AcU4xXnauLSsbRCow9@posti.anvianet.fi>
From: phl@netikka.fi
To: rsgb_lf_group@blacksheep.org
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 <562270DF.6060606@posteo.de> <4984ACE6DAD948639B45FCDA15692B5B@lindavideo>
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Subject: Re: LF: TX Toroid Material
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Status: O

Hello Ken,

For transformers I have used Amidon -77 ferrite material successfully  
on 136 and 472 kHz. Same goes for Ferroxcube 3F3 ferrite material.

For inductors in filters or chokes the Amidon -2 iron powder mix as  
suggested by Stefan has worked well for me on 472 kHz and I have seen  
it used in many working 136 kHz designs too.


For matching a 2 kohm anode impedance to 50 ohm using a ferrite  
transformer I would be very careful, you will really have to calculate  
the number of turns and get it right in order not to saturate the core  
since the voltage swing is large at the 2 kohm level at those powers.  
At least this is my humble non-professional opinion on the subject.


BR

Paul-Henrik, OH1LSQ


Quoting Ken <ken.h.wright@btinternet.com>:

> Hi Stfan.
>
> I have been looking at the 77 type material, but waiting for other group
> members opinion.
>
>
>
> 73
>
>
>
> Ken
>
>
>
>   _____
>
> From: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7FC
> Sent: 17 October 2015 17:02
> To: rsgb_lf_group@blacksheep.org
> Subject: Re: LF: TX Toroid Material
>
>
>
> PS: For the RF transformers i often use N30 ferrite material with good
> results. An AL of 4000 nH or above is a good choice. If you want to use
> Amidon ferrite cores, use type 77 material (available on most distributors).
> 73
>
> Am 17.10.2015 17:41, schrieb Ken:
>
> 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