Hi folks,
In my 137 kHz tx I also had an output filter. Trying to use all kind of
ferrites I noticed that they normally get rather warm (or hot with the
wrong type of ferrite) if I used it for some longer transmissions.
>From that point on I used air based coils.
If I am not mistaken: 56 turns 0,7 mm wire on a piece 40 mm pvc tube with
a cap on one end to fix the coil to the bottom of the tx chassis.
If somebody is interested I can dig out the coils from my junkbox to
verify the data ....
btw. I will be retired in a month. You can expect me back on 137 kHz after
that event!
73 Wil - pa0bwl
> I forgot to mention one important thing in my last reply:
>
> From the earlier discussions on this subject I got the impression that
> T130-3
> and T200-2 cores were suggested as alternatives to the 3C85/3C90.
>
> The mixes #2 and #3 are powder iron, not ferrite as the 3F3 and 3C85/3C90.
> I
> beleive they are poorly suited as power transformers on LF/MF but make
> good
> inductors for low-pass filters on 136 and 500kHz. This is true at least
> for the
> #2 mix. On 500kHz I remember seeing reports of severe LPF heating with the
> #3
> mix, I will have to check again on that.
>
> Some of the gurus please correct me if I'm wrong here. I just wanted to
> press
> the "pause and think again" button before someone possibly orders inductor
> cores to use for a transformer.
>
> I'm still a beginner/learner in this game, the above is just how I see
> things
> today.
>
> 73's
>
> Paul-Henrik
>
>
> Quoting "Johan H. Bodin" <[email protected]>:
>
>> Yes, 3F3 is even better than 3C85/3C90 for power transformation at a few
>> hundred
>> kHz. The 3F3 cores, if coloured, are light blue. Philips sold their
>> ferrite
>> business to Ferroxcube: http://www.ferroxcube.com/
>>
>> 73
>> Johan SM6LKM
>>
>>
>> Paul-Henrik wrote:
>> > Have a look at Ferroxcube (Philips) cores of 3F3 material. As far as I
>> can
>> > interpret datasheets for these, they should work fairly well as
>> transformers up
>> > to 500kHz with a DC component and up to 1MHz without DC.
>>
>>
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