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peeling the onion, slowly. I thought the problematic band was 15 Meters for SSB?? No its basically 20mhz and up as in all 15/12/10 for SSB. Allison

Now if one does all that and really wants 20 and up spurs and all.... Simple add an inline (between radio and antenna jack) 28mhz low pass filter. and leave it there.? If it well made it will be

Warren: I'm peeling the onion, slowly. I thought the problematic band was 15 Meters for SSB? Gordon: I don't understand what you are asking me. I provided the simulation file for the 80 meter filter.

Regarding ' Has anyone else thought of just designing a separate TX board for use with the V3/V4 ubitx?' I agree completely considering that many have a separate receiver already. Il 03/set/2018

Kees, Before you remount K3 remove the audio switching path from it.? Many get? feedback from that path.? Also it can be inserted form the bottom. Also the big issue is all the spaghetti traces.

Forgive me if this is way over simplified. I’m not an RF designer,? but couldn’t you manually just insert an appropriate LPF from your ant. connection to the antenna to reduce harmonics on that

Why use linear amp with lower efficiency for CW?? Class C can be shaped for keying and offer much mroe power with far less consumed.? However binding the two ubitx to a QSX amp is not easy.

Let’s do it… Sent: Monday, September 3, 2018 3:26 PM To: [email protected] Subject: Re: [BITX20] K5BCQ uBITX Relay Switched LPF/BPF board The QRP Labs LPF filters are rated at 10W according to Hans

Got it Howard. And I agree with both the strategy and the necessary amount of improvement. On mine, a six dB improvement would make all bands legal for CW harmonics. That would be a nice solution for

You can also? modify the existing filter for a faster roll-off which MAY catch enough of the 15m spur .....for instance. The plot labeled "1" is the original LPF, the other plot is the modified LPF.

You can also see, in the picture with the uBITX board, that the 2N3904's have already been pulled, waiting for the 2N2222A's ..............and other incremental improvements.?? 73 Kees K5BCQ

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