Hello Chris, Hello Clemens,

wish to share a couples of mumblings..
I don't know if the saturation formula used calculating B on 
transformers is valid also for inductors.. probably we should ask some 
more addicted guy, there is something that does not make me happy using 
it from an aestethical point of view but could be wrong ...
Beside this, 2kW on 50 ohm should mean rad(2000*50)=316Vrms not 600 I'm 
wrong?
Unfortunately I will probably cook my FET during the weekend so I have 
not yet 1 kW for testing.. but Chris let me ask: have you already 
checked the attenuation curve of your LPF? are you sure the LPF is 
correctly resonated? or could you excite your PA at lower frequencies 
and see if the behaviour is still the same?

I had the same problem with a PI LPF it was loading a lot the TX and 
heating a lot.. I made coils bigger and bigger but no changes.. 
switching to T type like W1VD design with coils made on T200A-2 (the 
T225A-2 were not available) solved all problems at power level of 3-
400W with good attenuation of armonics and very low insertion losses. I 
agree my power was one fifth.. but a check could be worth ;-)

GL de Marco Ik1HSS

----Messaggio originale----
Da: [email protected]
Data: 25-mag-2017 14.28
A: <[email protected]>
Ogg: RE: LF: Iron dust toroids and heating

Hello Chris,

>> I was wondering if the #3 material which is rated for use 
>>from 0.05 to  0.5 MHz, and has several times the permeability would 
be a better
>> choice for more power through it? 

>Yes that sounds like a good concept.

Look what the mini ring core calculator is showing (see attachment) and 
draw your conclusions.
The calculations are completely based on amidon data.
I've chosen 600V RMS ,that's the voltage drop across L2 at the 2kW 
level.
For #3 I had to resort to T200 size because 225 is not available for 
this material.

73
Clemens
DL4RAJ 

 

>-----Original Message-----
>From: [email protected] 
>[mailto:[email protected]] On Behalf Of DK7FC
>Sent: Thursday, May 25, 2017 2:09 PM
>To: [email protected]
>Subject: Re: LF: Iron dust toroids and heating
>
>Hi Chris,
>
>Am 25.05.2017 12:40, schrieb Chris Wilson:
>> I was wondering if the #3 material which is rated for use 
>from 0.05 to
>> 0.5 MHz, and has several times the permeability would be a better
>> choice for more power through it? It probably gives a higher Q with
>> fewer turns, allowing the use of larger wire without having
>> overlapping layers in the winding?
>>    
>
>Yes that sounds like a good concept.
>
>It is interesting to follow your plans. Actuelly i would like 
>to try to 
>build a  2.5 kW or larger PA as well, just for interest of course. I 
>would of course use it together with a dummy load only, 
>because you must 
>not radiate more than 1 W here in DL, and i am a conformist and under 
>the spell of authorities (german: autoritätshörig) :-)
>It would be interesting to deal with the problems that would 
>appear with 
>such PAs. For say 3 kW and the comfortable situation to have a 
>suitable 
>60 V power supply, i would simply build a current mode class D 
>PA, hard 
>keyed with an IXDD614CI and 2x 4x IRFP260N FETs. For the LPF i 
>would use 
>the T225A-2 together with RF litz wire, maybe 250x0.1mm, available at 
>https://www.spulen.com/hf-litze-250-x-0-1-mm-100-g-spule.htmland 
>WIMA-FKP-1 capacitors, the 2 kV version...
>
>Good luck and fun with your projects.
>
>73, Stefan
>
>
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