Re: uBitX CAT problem on 40m #ubitx #ubitx-help #ft8

Tom, wb6b

Eventually I'll set up a proper ground island and shielding (like put my uBITX in a case), but in the meantime I'm having success with these toroids on the USB Cat cable. The black cable, with one at the radio and one at the raspberry Pi. This also helps reduce the RF noise from the Pi while receiving.

The clamp-on filter, on the white cable, is for the connection to a USB audio adaptor. I used a 2-3/8 toroid on the HDMI cable.

Transmitting on 80 meters was causing my internet to quit. I wound the power and ethernet cable to my router through a 2-3/8" toroid and that fixed that. I placed a grounded shield (aluminum "mini loaf" pan) around the power supply for the internet modem to get rid of the noise it was causing in the receiver. Eventually, I'll move all the wiring for the internet elsewhere, as far as possible from my ham station. 

On a side note, I used one of the 2-3/8 toroids to make a 1 to 9 impedance matching transformer for my 55 foot long (stealth) 80 through 10 meter non-resonate antenna. I placed another 2-3/8 toroid (with 10 turns of coax) 25 foot down the coax of the antenna cable to block the common mode RF. (The shield is the main counterpoise) Amazingly, it is a fairly good match for those bands, but I normally use it with an auto tuner.

I purchased these toroids from Palomar Engineering. The small ones on the black USB cable, were rated for 1 to 10 MHZ. The large ones, if I recall, were 1 to 30 MHZ.

Tom, wb6b

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