2 (tr)uSDX Assembly

Alternative Bands Setups

We´ve got many user requests for alternative Band Setup. Personally we´re not really interested in that and lack the time to double- and triple check all the Information, but we wanted to give you -the user- the possibility to play around with it. Since (tr)uSDX is supposed to be a standardized rig, we cannot allow for totally custom Band Selection, but we´ve prepared 3 Options in Firmware for you:

Band-Slot AssignmentK1K2K3K4K5
Lo (current Standard)20m30m40m60m80m
Hi (Only Hi Bands)10m12m15m17m20m
Classic (Classical Bands w/o WARC)10m15m20m40m80m
Can be selected at in Menu 8.7 “Band Config”

Alternative, very comprehensive Schematic, drawn by KD4SGE & WA4ITD:

After Assembly, you need to install Firmware

Klick here to get to the Group Buy Instructions

Here are the Results of the Harmonic measurements:


The TRX was un-tweaked, and built completely according to the Schematic Values of Capacitors and Toroids. Harmonic suppression is better than -43dB on ALL Bands.

A Video on Filter Tuning

UPDATE: 16. March 2022 (Theoretical FDT86256 Values have been removed, as we have practical Values now) Theoretical BS170 Values still here for Experimentation.

Remarks for Alternative Bands Setups


The below Tables represent UNTESTED Component Values ! Use them with caution at your own Risk. The Values need to be tweaked for 5W@12V and Efficienct over 80%. Please report back in the forum about the Values that actually made it happen for you.

ATTENTION: This Table are THEORETICAL Values for 3x BS170 (Install ONLY Q1,Q2 and Q3 as PA FET)

F (MHz)3,565,357,0510,114,0518,0821,0524,928,05
This Table is for 3xBS170 (All Inductances in µH – All Caps in pF)

Depending on your Setup, you only need to place the desired Component-Values to the Right Band-Slots together with the FET you want to use and Activate it in Firmware.


CX0//CX1 ????

X Stands for Band slot (e.G. 1 for K1 -> so this would be then C10//C11)

“//” means: Those 2 are in Parallel. Putting Capacitors in Parallel is a simple Addition of Capacitance


CX0//CX1 for FDT86256 and 80m is supposed to be 1041pF

So we need to find 2 (available) Capacitor-Values, that will result in a total Capacitance closest to 1041pF as possible.

470pF//560pF would be close = 1030pF

620pF//430pF would be close = 1050pF

680pF//360pF -> BINGO = 1040pF

but a lot of other combinations are possible. Just use what you can get or have available and try to get as close as possible.

There might also be cases where you can achieve it with just one Cap. In this case place it to one of the 2 available Cap-Footprints and leave the other one empty.

Remember: (tr)uSDX Filter Capacitors ALWAYS need to be C0G/NP0 Types, rated for at least 100V !

Use some online or offline tool, to calculate the amount of Windings for your Toroids. I like this one: https://www.dl0hst.de/mini-ringkern-rechner.htm#en

Depending on Frequency you can use either T37-2 (Red) or T37-6 (Yellow) Toroids.

Happy tuning !