First rough draft at a daughterboard that allows off board right-hand-side filter switching..... without having to ​rebuild the filters etc.

Will check more carefully.   If anyone sees really stupid layout issue, please speak up.    Capacitors 0.1 uf   Inductors (surface mount)  100 microhenries.    

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From: BITX20@groups.io <BITX20@groups.io> on behalf of Kees T <windy10605@...>
Sent: Saturday, August 11, 2018 2:46 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Harmonics

 

All,
I'm going for some daughter boards to see how well this works (below). I still like using the exact components off the stock uBITX board. I would mount the 3 diodes on the uBITX board and the 2N3904 they drive on the daughter board, along with the 8 relays.

Hans,
What are the dimensions of one of the QRP Labs LPF boards (distance between the 2 sets of 4 pin headers and overall width/length and height with components of the board and if you offer unpopulated LPF boards. 

Michael,
I agree that a Nano would offer more flexibility as would a CD4028 for selection of additional filters beyond 4.....but the rework gets more complex and the cost goes up. Good luck to you and your design, that's what it's all about.

73 Kees K5BCQ

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I was thinking of something less costly.....such as: the existing  TXA, TXB, and TXC all drive 2 relays each (on both ends of the LPFs). Then you add a 3 diode "OR" to those 3 select lines to drive the 4th relay which, in it's normally closed state, "has picked" the 4th LPF (as it does today on the uBITX). Activation of any of the three pulls it "off" the LPF and grounds it. That would only require 3 diodes and a 2N3904 driver for 4th relay.

RF IN and RF OUT is bussed to the 4 relays.