|To:||"Alberto di Bene" <[email protected]>, [email protected], [email protected]|
|Subject:||LF: Re: [Lowfer] [TECH] Help needed on toroid trasf. construction|
|From:||Frank Gentges KØBRA <[email protected]>|
|Date:||Mon, 11 Jun 2001 10:06:03 -0400|
Alberto,To wind such a transformer you can use the Amidon FT50-J core with an initial permeability of 5000. for a 10 kHz bottom end you will need about 17 turns for a 50 ohm source/load. For the other 4:1 side you will need 4 times that. With separate windings it will start dropping out at about 10 MHz. To extend it higher you will need to twist wires together for a 5-filar winding. The 4x winding is made up of 4 of those all connected in series. I use Radio Shack wire wrap wire here which is readily available. However, to get 17 turns of 5-filar wire wrap wire on that little core may be too hard. You may either go to smaller wire or a larger core such as an Amidon FT87-J core.
In any event I will be glad to wind up such a beast and send it to you. Before I start, let me know which side is 50 ohms and is the other side 4x50 = 200 ohms or is the turns ratio 4:1? Or is the 4x side 50 ohms and the 1x side 12.5 ohms or 1/4 the number of turns? How much space is available?
I wound a similar 1:1 replacement for the TenTec RX320 which made a real difference.
Frank K0BRA At 01:34 PM 6/11/01 +0200, Alberto di Bene wrote:
Hi all, I need some words of wisdom and a bit of help about the construction of a small toroid transformer. First the antefact : I swapped recently my TS-850 for a TS-950SDX, a very fine radio, but much less sensitive on the LF band than the TS-850. Looking at the schematics, and doing some filter simulation with Electronic Workbench, I think to have found the culprit, i.e. L3, a small toroidal transfomer, with ratio 1:4, which is inserted in the signal path, after the input attenuator, and before the filters bank. With all probability, its response at 136kHz leaves much to be desired. The TS-850 doesn't have any such transformer, the signal goes straight to the filters. So I have decided to replace it. Looking in the MiniCircuits catalog, I have found what seems to be the ideal replacement, the T4-6T-KK81 model, which has a -3dB response from 10kHz to 100MHz. Problem is that this transformer is not carried in stock by the Italian distributor, and both they and the MiniCircuits sales office have a minimum quantity amount for an order.At this point the only choice is to build it myself. And this is were your help couldcome in my rescue. I need to know what your experiences are in building such a wideband kind of transformers. What is the best type of material, caveats to not forget, optimal number of turns, you name it. TNX for any help, 73 Alberto I2PHD To unsubscribe, send to [email protected] "unsubscribe lowfer" (Do not send to list!!) Send on list submissions to [email protected]
Frank Gentges KØBRA [email protected]
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