Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
It looks like the filter is designed for 50 ohms in and out. The transformer
inductance is also a part of the filter. It's value should be about the same as L1 so to use it at 50k to 200K, you'll need to rewind for a lot more turns on the primary and both secondaries if you keep the same core material. Scaling it all and then optimizing for Coil Q of 40 and regular cap and coil values, I get new values like: L1 680nH - 100uH C1 470pF - .022uF C21 180pF - .027uF L2 1.8uH - 100uH C22 470pF - .022uF T1 680nH (13:6:6 Turns) - 100uH (1911:882:882 Turns) I strongly recommend changing T1 to a much higher mU core material. This should result in -3dB points at 50 and 200 kHz, flat pass-band and -30dB at 20 and 500 kHz. Good luck finding a 50 Ohm antenna at these frequncies. An active antenna may be the way to go, otherwise you'll need many acres for all the wire. On Sun, 11 Sep 2005 12:09:16 -0400, TRABEM wrote: I am trying to scale an existing front end receiver (butterworth bandpass) filter to a different frequency range. Unfortunately, it has a transformer in the original design, so I'm stuck. I also don't know how to handle the load presented by the active front end component other than it's probably not significantly reactive. The existing filter is for a 7 Mhz receiver, I'd like to have a similar filter design for 50 to 200 Khz. The filter components and transformer winding details are in the document at: http://www.amqrp.org/kits/softrock40...0Assy%20v1.pdf The input chip is an FST3126, spec sheet is at: http://www.fairchildsemi.com/ds/FS/FST3126.pdf The spec for the T30-2 transformer core is at: http://partsandkits.com/T30-2.htm I have aade filter design software, but it isn't allowing me to plug in the transformer into the design page of the software....so, I need to know it's equivalent circuit I think. The transformer winding details are on page 4 of the document and the schematic of the front end is page 9. Ultimately, I need new values for L1, L2, C20, C21 and C22. If someone can give me a reasonable guess as to the equivalent circuit of the transformer and the IC (U5), I can do the rest of the job myself using the aade filter software. Thanks, T |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Phone line as SW antenna [04-Apr-00] | Info | |||
Phone line as SW antenna [04-Apr-00] | Info | |||
Variations on the channel TRF AM tube tuner; and a question | Shortwave | |||
Phone line as SW antenna [04-Apr-00] | Shortwave | |||
Phone line as SW antenna [04-Apr-00] | Info |