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SCWIS, or anyone, I remember that a filter was calculated for 13.560, but here in France I cannot use that frequency, so I need a filter for 13.870mHz. Can you help?
Thanks !
SCWIS, or anyone, I remember that a filter was calculated for 13.560, but here in France I cannot use that frequency, so I need a filter for 13.870mHz. Can you help?
Thanks !
Bertrand at Radio Bon Esprit
Total posts : 45366
Total posts : 45366Thanks Neil,
But how to find 0.1000 uH 0.4613 uH (or 0,5) and 1.30 uH components Does it exist ?
My problem is that with the present filter (13560 kHz) I have a great loss of power, using Power Pixie withe Q1 2N2219 and Q2 2N3053. After the filter, HF power does not exist anymore. Does it come from the filter ?..
Thanks
Total posts : 45366It is not likely that a filter designed for 13.56 MHz would have significant loss at 13.8 MHz because standard designs set the cutoff frequency at about 1.2 times the “nominal” frequency. Maybe something else is wrong. You could try decreasing the capacitor values by about 10% but I don’t think this will work.
As for calculated parts values, there are a couple of ways to find parts for filters. One is to use the closest standard values. For this type of low pass filter use the closest smaller standard value for the inductors and capacitors. This will raise the cutoff frequency but there is plenty of tolerance for this before the second harmonic will pass. Generally, these filters are designed to have the cutoff frequency 1.2 times the operating frequency. There will be little harm if this is raised by the smaller value components (within reason).
Another approach is to wind your own inductors. This would involve obtaining some toroid cores suitable for the frequency of operation and calculating the number of turns required.
The loss you observed could be due to the filter if the inductors or capacitors have high loss at 13-14 MHz. Using the correct toroid cores and low loss capacitors I have observed loss of about 1 dB (about 11%) in a 5 pole filter at 1680 kHz.
You might also consider the use of the 2N3053. This has a rather low gain-bandwidth product (Ft) of 100 MHz. One with an Ft of 300 to 500 MHz would probably work better.
Neil
Total posts : 45366Thank you Neil,
I checked the filter, apparently, nothing wrong. But still a little power at L4/C8 and nearly nothing behind …
What do you think of the 2N3553 for example ? (Ft = 500) (RF performance = 175 mHz)
Bertrand
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