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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th Jun 2018, 5:40 pm   #21
Argus25
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Default Re: Amidon and Micrometals toroids.. other brands ?

Quote:
Originally Posted by jpdesroc View Post
I have some 330uH@3.3A (100mOhms) powdered iron toroids on hand..
The 330uH would give around 2.9k ohms@1.4Mhz.
I would put 0.1uf on each side of it to the ground..
It would work, but anything in the region of 10uH to 50uH would probably be plenty too. One trick to avoid having to have another core or toroid is simply to thread a few ferrite beads over the tinned copper wire that leads to the center tap and the bypass capacitor.
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Old 7th Jun 2018, 6:29 pm   #22
Jon_G4MDC
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Default Re: Amidon and Micrometals toroids.. other brands ?

I have enjoyed this thread very much.
Just one thing - the CB transistors specified in the Chris Honey design now hard to obtain.
You still find them listed but in my experience, if you buy, what you get are fakes.

There are Semelab parts D1001,D1002 etc - same story. Some I received had been re-cycled!
You could see milling marks on the tabs where old solder had been removed. It's a mine field.

Also forget to mention in connection with original topic..
What do we know about Palomar Engineers? They have also been a source of Iron-dust and Ferrite cores I think.
Is it just an alternative name?

Last edited by Jon_G4MDC; 7th Jun 2018 at 6:35 pm.
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Old 7th Jun 2018, 10:27 pm   #23
Argus25
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Default Re: Amidon and Micrometals toroids.. other brands ?

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Originally Posted by jpdesroc View Post
Very informative stuff you gave me here..
Nowhere on the net I could find a nicely explained example
of how to 'understand' these transformers behaviour,
specially at low frequencies..
Only some fraction of the useful information that exists is on the net, after all it has to be scanned & uploaded, much of it is in historical textbooks in every field of science. I have a library of very useful information in books and much of it is not on the net yet. If you tell that to a teenager they won't believe you. For example I have some equation solutions in one book that are not available anywhere on the net. There was a science TV show in AU where a fellow got a prize for a "new invention" the Judges googled it and it wasn't there, but it was in Popular Mechanics magazine 1930 or similar just not on the net.

One other point, if you are using different transistors to the ones I used, the bias resistor may have to be altered so the voltage drop across the 1N4004 is about right for the particular transistors , and possibly a low value resistor might need to be placed in series with the 1N4004. In any case, when your amplifier is finished, you will need to load it into an appropriate non inductive 50R dummy load and feed it with a generator and examine the output on the scope to make sure all is well.
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Old 7th Jun 2018, 11:08 pm   #24
jpdesroc
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Default Re: Amidon and Micrometals toroids.. other brands ?

[QUOTE=Argus25;1050002]
Quote:
Originally Posted by jpdesroc View Post
Very informative stuff you gave me here..
Nowhere on the net I could find a nicely explained example
of how to 'understand' these transformers behaviour,
specially at low frequencies..
Quote:
One other point, if you are using different transistors to the ones I used, the bias resistor may have to be altered so the voltage drop across the 1N4004 is about right for the particular transistors , and possibly a low value resistor might need to be placed in series with the 1N4004. In any case, when your amplifier is finished, you will need to load it into an appropriate non inductive 50R dummy load and feed it with a generator and examine the output on the scope to make sure all is well.
I will not use the 2N5945's in your schematic.
I don't have any and they list around $30.00 each on eBay!!
Way too expensive for my project..
BUT I checked in my power transistor bin and found some
MJE15028G power NPN's rated at 30Mhz min, 50W, Vce 120v and Ic continuous 8amp.
https://www.onsemi.com/pub/Collateral/MJE15028-D.PDF
I know this is not the 'normal' transistor to pick up
for such a project but I should give a try
since it will run at a low 1,400khz freq. carrier.
I tested the hfe and it stays around 100 up to Ic = 2.5amp.
The hfe starts to drop a little passed 2.5amp.
Your feedbacks are greatly appreciated !
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