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Here's a corrected version of that chart showing how TXA,TXB,TXC get mapped to specific bands.
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Corrections are:? 30m should read 10m for 30mhz,? ?and? "else c=0 for 40m, else 80m". Note that the 10m LPF also handles 12m and 15m, the 20m LPF also handles 17m, the 40m LPF also handles 30m,? and the 80m LPF also handles 60m, true for all versions. I've added a third line to show Allison's hacked v3,v4 board, which fixes the LPF harmonics. The symbols a, b, and c refer to signals TXA, TXB, and TXC from the Nano out to the three LPF relays. ########################## Here's what the routine setTXFilters() does in the firmware for v3,v4,? and? v5,v6.? Also v3,v4 with Allison's hack: ? ? ? ? ? ? ? ? ? ? ? ? 10m? ?20m? ?40m? ?80m
ver 3,4:? ?abc = 000? ? 100? ? 110? ? 111? ? ? ? # a=0 for 30m, else b=0 for 20m,? else c=0 for 40m, else 80m
ver 5,6:? ?abc = 000? ? 100? ? 010? ? 001? ? ? ?# 1 to engage each filter for 20m,40m,80m,? but 30m is always inline
allison:? ? abc = 000? ? 010? ? 001? ? 100? ? ? ?# hack to v3,v4,? now similar to v5,v6 boards except filters ordered differently
On Wed, Jan 15, 2020 at 08:25 AM, Jerry Gaffke wrote:########################## Allison, KB1GMX, gets major kudos for this fix addressing the LPF harmonics, which Farhan then used on v5 and v6: ? ??/g/BITX20/wiki/uBITX-spur-and-harmonics Allison kept the physical placement of the v3,v4 filters the same as much as possible to avoid excessive rework,? Farhan ordered them logically on the new v5,v6 builds.? Allison's hack can be made firmware compatible with v5,v6 boards by either swapping around the TXA,TXB,TXC signals via cutting traces and adding wire jumpers, or by stuffing all the LPF L's and C's differently. Unfortunately, it's a lot of work to do all the mods required for Allison's hack, and difficult to verify without a spectrum analyzer. Replacing the relays with Axiom parts on v3,v4 boards is easier, adding an outboard LPF filter assembly is easy and thorough. It is possible to operate the uBitx on 160m.? But for all versions, you must add a low pass filter appropriate for 160m? in line between the uBitx and your antenna to cut down the harmonics.? Otherwise the 3'rd harmonic will be? almost as strong as your 160m fundamental. Jerry, KE7ER Here's what the routine setTXFilters() does in the firmware for v3,v4 and v5,v6 boards: |
