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David, Manual switching is only one of the options. There is also a small board you can add which can mux the 3 bits from the Raduino to all 6 sets of relays......but it would require a small code

Thank you, Alyson, for even more education I’m just about finished building a UHF repeater for emergency work, and I’ll be able to turn back to this rig at some point. I don’t need it to work

Yep, sorry, you were lowering the impedance, raising the capacitance. Slip of the tongue. (I use Siri) You might tell us how you changed each value in those filters.

Start with 1V is adequate as the dive is Current not Voltage for transistors. Altering the resistors make the previous stage a bit happier and lower the loss to the resistors but the basic issue is

The QRP Labs LPF filters are rated at 10W according to Hans Summers, the BPF filters he sells are not, probably because of the series current the capacitors have to handle or larger inductors

Gordon: Thanks for your concurrence. To prevent others from being confused, I am raising not lowering the capacitance, which I am sure is what you meant. And yes, I am trying to come up with an easy

Howard, I get your point. And a six DB improvement makes the device a much better transceiver per the regulations With simple unshielded wiring to three external relays, in my tests I found the fifth

Warren: The fifth and the 7th are at -45dB now. You are missing my point. The design of the filter directly effects the level of the harmonics. Yes, the stray? capacitance creates a "sneak" path

First there are two issues one being poor harmonic filtering and Kees is addressing that here. The other is spurs from inadequate filtering above 17M,? That requires band pass filters before the

Kees: Why manual band switching? Could not the code select the proper filter according to frequency the user selects on the uBitx? Could not the RF Switching be done using pin diodes or FET switching?

Howard When I measured 80 meter harmonics the particularly troublesome ones were 5th at 18 MHz and 7th at 25 MHz. In both cases the attenuation of the stock uBitx at those frequencies was limited by

Kees & Group: Please Clarify: I thought I was told some time ago on this post that only passband filters would address the uBitix issues. If that earlier statement was correct, why are people working

I previously mentioned that I would try to reduce the harmonics by changing the output to 25 ohms and adding a step up transformer to go back to 50 ohms for the output. This would allow tripling the

An alternate improvement is replace Q10/11/12 with mmbt2369 or BFr106 as the 3904 is not impressive at 45mhz. Allison

Henning, There are errors in the diagram and the levels are really different than shown. Looked at your diagram and its assumptions are wrong.? If the final mixer can accept -1dbm without producing

Lawrence G., I tried a few things along that path.? made matters worse and that was also tried with external level 7 mixer and level 17 external mixers.? ?It was then a rock fell on me and I

That’s funny! Best little joke today!! Even a novice in my day knew that kind of stuff. Oh how times change !!

MRM, The not so funny part Is I've been saying that for over two years and especially the last two months. The whole idea of minimally filter 3-30 mhz radio is wishful thinking.? When I first said

I solved the root cause, an open wire. But, now the Arduino does strange things, it locks up, sometimes I get very distorted CW xmit waveforms. The mystery continues.

There is also the outstanding, yet related, issue with switching sidebands on CW (i.e. CWU to CWL or vice versa) with KD8CEC's code which I had? previously documented.? Try this on any commercial