Old LOPT fm TV'S work well 3C85 cores --make sure there is no gap between the
two halves when re assembled
No cost ie scrap value
G3kev
Sent from my iPhone
On 17 Oct 2015, at 22:09, DK7FC <[email protected]> wrote:
> Hi,
>
> I took a FT-240-77 in my large PA a while ago. The primary winding can be
> seen here:
> https://dl.dropboxusercontent.com/u/19882028/MF/20130713_002528.jpg
> 47 turns were fine to switch a 475 kHz (nearly) rectangular signal with an
> amplitude to 320 V. From that, you can calculate the number of turns you will
> need. Let me think: A sine wave causes a lower peak flux in the core, so you
> are on the safe side. So you are on the safe side. 230V rms for 47 truns. If
> you want to run 300W at 50 Ohm, that's U=sqrt(P*R)= 78V rms, i.e. 47*78/230=
> 16 turns for the secondary winding. If your primary side is at 2.1 kOhm, you
> need sqrt(2100/50)*16 = 104 turns. You can use thin wire on the primary side.
> 104 turns is managable and the losses in the transformer will be low! A
> series C (1 uF MKP-10 1.6 kV maybe) to the primary winding may be needed to
> decouple DC. Then you are down at 50 Ohm and can use the well known double-pi
> LPF designs using 6.8 nF (-j50 Ohm) and 16.7 uH (j50 Ohm)... For further
> calculations are needed. Beware of simulations! :-)
>
> 73, Stefan
>
> Am 17.10.2015 20:50, schrieb [email protected]:
>> 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
>>
>>
>>
>
|
