# Raspberry Pi rpitx for SSB with filter?

Using rpitx, we can transmit SSB using a single GPIO port from the Raspberry Pi. This of course uses square waves so creates a lot of harmonics.

If I were to use a couple of daisy-chained 70 cm bandpass filters on the GPIO output, would there be any harm in using this output for ham radio?

My aim would be to either connect it up to a PA, or to an upconvertor to go to 2.4 GHz for Es'hail-2 usage.

I understand that it wouldn't be the "cleanest" signal, but would be be legal and usable?

• A spectrum analyzer would be advised to ensure you're not transmitting a mess of spurious trash (despite your filtering). Also, don't forget that most USB power supplies (which you'll use to power your RPi) are very noisy. Make sure that too is clean. – Synchros Apr 24 '19 at 20:08
• 434MHz USB output from RPITX version 2 starts at 6:22 of this YouTube video. I am surprised to see that the carrier and opposite-sideband rejection are quite good. Results of a two-tone test would be very interesting. – Brian K1LI Apr 25 '19 at 20:08