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 <[email protected]>:
Hi Stfan.
I have been looking at the 77 type material, but waiting for other group
members opinion.
73
Ken
_____
From: [email protected]
[mailto:[email protected]] On Behalf Of DK7FC
Sent: 17 October 2015 17:02
To: [email protected]
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
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