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Old 19th Mar 2019, 11:10 pm   #16
MrBungle
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Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: Homebrew SSB Transceiver

Your filter values are way different to mine on 20m. I wonder if there's a mismatch between stages. I've got a 3dB point of 16.4 MHz, 30dB down at 22.5MHz. Insertion loss at peak is around 1-2dB. My calculated values were normalised for off shelf capacitors. I can't remember where I got them from, possibly GQRP club. I've run the inductors through toroids.info based on the values presented:

c1 - 180pF
c2 - 390pF
c3 - 390pF
c4 - 180pF

l1 - .773uH - 14t T50-6
l2 - .904uH - 15t T50-6
l3 - .773uH - 14t T50-6

Terminating 50 ohms at one end shows a flat VSWR and 50 ohms in the pass band on my MFJ259 analyser. Swept with my AWG and power meter and it's about right. I think it was about 50KHz off. I didn't check return loss as VSWR was good enough to worry about dB here and there.

I used T37-2 toroids, which was a bad idea as they get rather hot!
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