I spent the first 10 years as a ham QRP and worked the world and I was lucky to have a dipole and vertical (vertical worked better). Now 40 years later I'm getting back in and going QRP w/ EFHW.?

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Be very careful playing on 160m in the uBitX stock configuration. ?The PA easily puts out over 30watts with the second and 3rd harmonics to join the party as well. ?You should have a fuse in-line to stop the fets letting out the smoke. ?There is no ALC to tame the amp at low frequencies. ?Plus with the small heat sinks the fets go into melt down quickly.

The problem with relying on tuners to cut harmonics is it is hit or miss. I have a L network tuner I use. Sometimes, on some frequencies, my antenna is in near prefect tune and the matching box is basically passing the transmitter output direct to the antenna. In that case the L network has no chance to act like a low pass filter and remove anything. Maybe there are other tuners that stay in circuit, even when the antenna is a match, with some resonance to possibility act as a band pass filter.?

Tom, wb6b

Would something like this on the output help?

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.arrl.org/files/file/Technology/tis/info/pdf/8809017.pdf&ved=2ahUKEwjGlvW8m4zdAhUn54MKHSfJCSQQFjABegQIBxAB&usg=AOvVaw3uTeG3YM8UtUS_8W-P5N5V

Bill K8UH,

I think part of the problem here is many get posting one by one in the Email
and from moment to moment they have at best a vague notion of whats
going on till it grabs there attention. The problem then information and
postings are history that has gone past them.

I seriously wonder how many see this in the web format where scrolling
back is as easy as the mouse wheel.? ? Even with the web form if it not the
top 20 active threads it goes into the second of nth page and gets lost there.

Its why stuff gets, needs to be repeated so often.? Maybe the wiki function need to??
be populated.?

Allison

John:
Unfortunately, my uBitx Raduino died,and i haven't had the time to fix it and test my circuits. I should get to it this week.However the simulations are clear, it will work. The fix though is to change the impedance to 25 ohms, of the filters, which allows the capacitor values to triple.That reduces the effect of the relay capacitance. The output transformer needs to be rewound, the filters changed, and a 1:2 transfomer added to get back to 50 ohms. That is the only artwork change, the transformer.

Howard
Quoting John KC9OJV <greusel@...>:

I'll check the finals. I have some spares, just in case.

I'd love to be able to control the power out on the uBitX without opening it up and turning a trimmer pot. If it had a control for output power, I'd use it. The stock machine, as I'm sure you've noticed, doesn't have a way to reduce the output power.

So it is what it is. Perhaps I was naive that it wouldn't blow up while trying to tune for a few seconds.

Based on what you have told us.? Beats us.

Likely finals.
First without a load assure yourself the power supply is ok.

The easy test for fried finals is pull the wire that power them
(and them only). I think it s brown.

Also hint if you are running more than 10W on any band, surprised
you should not be when heat gets them.

Allison

On Wed, Aug 1, 2018 at 10:24 AM, iz oos wrote:

I would use ferrites with permeability close to 800, not the powdered iron toroids like the red and the yellow you have selected (permeability is less than 10).

For a parallel-resonant transformer, we don't want an excessively high permeability; what we want is the core material which will provide the highest Q at the frequency(ies) of interest.? The high-side winding impedance should present a reactance which is near the geometric mean (gm) between the 50 Ohm input and the? Antenna's feed impedance at its end (1500~4500 Ohms).? A 49:1 impedance transformation (7:1 turns ratio) presents a nominal impedance at the antenna terminals of 2450 Ohms as has been previously stated, and for this case the gm is ~350 ohms.? The reactance of the coil in the parallel circuit should be equal to the gm on the lower/lowest band of intended use -

I.E. a T80-2 (red) toroid with 36 turns #24 = 7.13uH.? The reactance at 7.0Mhz is ~315 ohms... close enough for our purpose.? On 40 meters a capacitance of between 65pF and 75pF will resonate the matching unit across the band, assuming the antenna wire is resonant (presents zero reactance) at ~7.100Mhz.
On 30 Meters, the same coil will present an inductive reactance of ~450 ohms, and require 32~38pF of capacitance to resonate the system, assuming the wire is resonant (again, zero reactance point) within the 10,100 ~ 10,150Mhz band.
So, a single -Resonant- EFHW tuner can be used (with separate, resonant antenna wires) on two adjacent amateur bands, I.E. 40 & 30 Meters.

On 20 Meters, the reactance of the coil is on the order of 630 ohms and required capacitance on the order of 18pF, and both of these figures present difficulties in actual implementation.? In the first issue, a gm of 630 Ohms suggests an antenna impedance of well over 6000 Ohms, which is un-achievable in nearly all terrestrial environments; the second issue is that the 18pF figure is inclusive of stray capacitance, which may be 10pF (or more) depending on materials and physical construction...? this will make tuning on 20M very sharp, and offer only a very limited tuning range because the minimum capacitance of the variable capacitor may well be equal to the capacitance necessary to resonate the antenna system.

Having two separate [switched] coils makes it possible to cover 4 or 5 bands with a single matching unit - 40/30 Meters on Coil #1, and 20/17/15 Meters on Coil #2.? Two wires will? cover four bands: A) 40/20 Meters, and B) 30/15 Meters...? a third wire is required for 17 Meters, if desired.

The gm for 40 & 30 Meters is 8.33Mhz, so the T80-2 coil should have a reactance of 350 ohms at this frequency; which is 35 turns on a T80-2 toroid.? The total capacitance necessary to resonate the system at 7.0Mhz will be in the range of 70~80pF, and at 10.12Mhz will require 30~40pF to resonate the system, minus whatever stray capacitance is present.

The gm for 20~15 Meters is ~17.52Mhz, so the T80-6 coil should have a reactance of 350 ohms at this frequency; which is 27 turns on a T80-6 toroid.? The total capacitance necessary to resonate the system at 14.0Mhz will be in the range of 36~44pF, at 18.13Mhz in the range of 20~28pF, and 15~20pF at 21Mhz, minus whatever stray capacitance is present.? The 15pF figure at 21Mhz is very low, indicating that tuning on 15 Meters will be rather sharp, that tuning range may be limited, and that efficiency will be a bit lower on 15 Meters (depending on both stray capacitance and stray inductance in the actual construction).

Denis,
Lots of static crashes, and very few signals.??
Dan, W2DLC

Step 1: Out with the DVM.
73 de ZL2DEX

I was tuning up on 160m, and the poor thing went dead. Won't power back up, either. Looks like I need to tear it down and find what mischief I did.

Finals? Or power supply? Suggestions from the symptoms?

73,
NG3P

Chris, what’s your antenna setup like? I am also on 40m CW, but in Ohio.

73

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Dan,

I have been calling CQ on and off from 3:00PM CST and nothing. I am not hearing much on 40M. Will look for you later.

Denis, WB8SKP

Hi Brent,

First,I cannot comment on whatever an l-match is unless you an l-network to match the transmitter for 50 ohms. The usual configuration has the inductor in series and the tuning cap to ground at the output end. That configuration is low pass and is just what the doctor ordered. One of the other configurations is high pass and will not help.

Low pass type antenna tuners have been cited as reducing the harmonics to legal levels in the U.S. I am using such tuners here while I am also building low pass and maybe band pass filters to go in-line between the transmitter and everything else downstream.

If we twist all knobs full right and change resistors to try and get a couple more watts (of overdrive?) then nasty byproducts get much worse. HF Signals says the microbitx is a ten watt radio on 80 meters and the power out drops as we go up in frequency. That is how I treat mine.

As for the olde daze, the required specs were a lot more lax than now. I'm sure you must have heard about all the RFI and TVI caused by hams using those old rigs (even though they were new at the time). Your comments are comparing apples to bananas. To quote one of my grandfathers, "the only thing good about the good old days is they are gone".

Those undesired products are removed with some types of tuners. I think Allison delineated some of them including L-networks. She has provided a lot useful info here. Others are working on internal mods to improve the uBitx performance and I will probably add something to mine. Later. Anything worthwhile along that line is going to be major surgery. The box I made for mine may not have enough space for any daughter boards. Hint, hint.

Let me recommend the CEC software for your uBitx after you get it working. Search terms include "KD8CEC", the author of the software. I am not using all the features available with his software but it makes the uBitx much more user friendly and makes CW really usable. I made a simple mod to control the CW sidetone level. Without that your ears will bleed. I am living without AGC or S-meter. They are not needed by me but you may want them for yourself. Louder is S-more and weaker is S-less:)

If you add all the mods with available kits and include the larger, touch screen displays the overall cost is much less attractive. That does not matter to some of the uBitx owners. Some of bought to experiment and lean. Enjoy *your* radio.

73,

Bill KU8H

--
bark less - wag more

Adam,
The microphone is polarized.
The switch you had received is connected between PTT line and GND and not in series with the microphone.
The microphone is connected between GND and Mic input. On the microphone capsule you can see that one of the pads is connected to the aluminum shell. That pad goes to GND, the other pad to Mic input.?
When you press the switch you should hear the relays engage and see an increase in current consumption. When you speak the current consumption should increase.
Don't forget to have a dummy load or an antenna attached to the Ant connector.

73,
Ion

VA3NOI

I gave several calls.? I'll come back in about an hour and try again.??
Dan, W2DLC

I'm calling CQ right now on 7.277MHZ.? I don't hear anyone else.
Dan, W2DLC