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Today kids probably can't even buy razor blades :-((? Steve kb1chu

on the 3 pin power plug on the ubitx the middle pin is the pa and the pin to the outside edge is the board power

Be careful, how that PFET thing works is tricky.
Several "how I done its" are out on the web with the PFET in the schematic drawn backwards.
Here's some old threads on reverse polarity protection, everyone has an opinion, some have several.
These point to posts specific to the PFET, but there's plenty more in the threads.
? ??/g/BITX20/message/35632
? ??/g/BITX20/message/35434

Vince
How many ppr did the one you used have? I have a piece of 2 inch aluminum bar stock that I was going to turn down for the knob and possibly for the flywheel if it is needed.
--
Allen ?Merrell

Surprised someone has not mentioned using a P-channel power MOSFET for reverse polarity protection this low current application.
(I think someone has on an older thread that this is re-hashing)
You can find them with pretty low Rds these days.? ~ 0.06 Ohms.
That rivals the contact resistance of a relay, plus no power consumed by energizing coils.
(the power loss trade off is power consumed by the relay coils verses the difference between relay contact resistance and Rds)
We are talking < 500mA here.?

I quickly found an app note from TI.


Regards,
Gary
AG5TX

THANK YOU KEES K5BCQ for your wonderful service to the uBITX community.

Mike N6CMY

Allison
Thanks for all mod proposals and great discussions. Just got my v3 unit after two month of delivery struggle throw the postal service here in Sweden. Now starts all the fun. I have one question that I think partly has not been covered by this thread apperently as it is about power mods. However, Farhan stated the the RX NF should be around 14 dB as there are no preamp and a passiv diod mixer. Perhaps OK for lower band but how about 28 Mhz. I saw in your final? mod statement that you had change the post mixer IF transistor to a better Ft version? BFR 106. I guess that will improve the NF slightly but is it enough. Will there be a need for a preamp also on the Rx side for the higher bands? Of course you can always argue that with low power output there are no advantage to hear stations you can?t reach. But if you hang on a 50 W PA I guess there is a need for some kind of improvement of the receiving performances at least on 10 M. And will the replacement of Q 10 also include change of C11 to 470pF and R13 to 8.3 ohm to boost 30 MHz?
Ulf sm0cgl since 1959

Thanks

I used one of those on a CB-to-10 mod I had done. I had to modify the software to ignore some pulses from it 'cuze it was too sensitive. I made the knob for it out of 2.5" aluminum round bar. Give that thing a good spin with that knob on it and it turns for a good long time! But to make a fine adjustment, no problem at all. Clean and smooth.

Vince - K8ZW.

--
Michigan VHF Corp.

I assume you were vaguely pointing in the direction of the relay trick, powering the coil through a diode.
That's a good solution, one I might use for a KW rig someday
Or even 100 Watts.
Though I'd still have a fuse.

For the uBitx, and me not being a mechanical engineer, diodes and fuses seem quite appropriate.
This rig has too many relays already.? ;-)

Reversing diodes shorting/ blowing fuses and diodes in series with power leads, brute force, works but is quite unnecessary. See more far more elegant solutions at .

On Thu, Jun 7, 2018 at 9:27 AM, bobh_us

<rwhinric@...> wrote:

Microsoft has done a good job with Minecraft after buying it from Mojang. I’m keeping an open mind.

If you notice a lot of high-frequency hiss in the receive audio on your BITX40 there is a simple remedy for this.
(This might be more noticeable if use headphones while operating.)?

There is a little know feature described in the LM386 Application notes called "Bass Boost".
By simply adding a capacitor and a resistor in?series between Pins 1 and 5 of the LM386 you can taylor the audio response of the amplifier.?

Wayne Burdick, N6KR (of Elecraft Fame) has been utilizing this trick for years, starting with many of the QRP Rigs he designed for the?
Norcal QRP Club.?

I used the capacitor and resistor values specified in the Norcal 40a schematic with good results for both CW and SSB receive.
These are 0.01 uF capacitance in series with 1.8 K ohms between pins 1 and 5.

You can try this by tack soldering the capacitor and resistor together and carefully touching one end of the pair to pin 1 and the other to pin 5
on the LM386. ?If you like how it sounds you can make it permanent. ?I was too lazy to remove my BITX40 board to install the parts
on the bottom of the board so I just tack soldered the pair directly to the pins on the chip on the top side of the BITX40 board.?

Cheers

Michael VE3WMB?

P.S. This is an LM386 trick only so it will not work on the uBITX.?

BITX QSO Afternoon/Evening, Sunday, June 10, 3PM & 7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere.

Join us as we make contacts with our BitX-40s or uBitXs or anything else on 7.277 MHz in 40 meters!

This is a worldwide event for BitX40 (and other QRP)?stations starting at 3PM and 7pm in each time zone. To participate, call CQ BitX on Sunday, starting at?3PM and/or 7PM?your local time. The BitX QSO Night continues through the evening and conditions usually improve after sunset, so it is worthwhile to participate later in the evening.

Suggested Best Operating Practices:

Work at QRP power levels unless conditions require more power.
Call and listen for CQ BITX on the hour and every quarter hour.
It is helpful if you call CQ BITX with your callsign, name and location.?
Repeat your callsign a number of times during your CQ BITX and during QSO's.
Start a QSO by confirming the callsign, location, name and signal report of the other operator.
Say the callsign, name and location of the other operator so others can hear.
If the frequency is busy, avoid long conversations.
After your initial QSO is complete, ask if there are any other stations who would like to contact.

Report your QSO's, discuss propagation, noise, signal reports, audio reports, antenna type, etc. in this thread.

This is an undirected, scheduled event.? The BITX QSO Night relies on you to call CQ BITX to initiate contacts with other stations, so warm up that final and transmit a few calls on Sunday evening.? Talk to you then!
--
John - WA2FZW

I have been looking into using a different encoder, I have an optical 400ppr which is very smooth (fresh from China) looks to be good quality but is close to 2 inches in diameter. I ran across a neat looking capacitive ?unit that can be set from 48 ppr to over 2000 ppr ?which looked interesting to me. They say they have a longer life than the magnetic or optical. The one I was looking at was made by CUI ?and the number of it is AMT103-V. I ordered one from Mouser. The shaft goes through it which I close to what I wanted . I plan on using a bearing on each side of the encoder with a flywheel (metal disc) on the back side which should have a good free spinning motion. Speed is going to depend on how fast the arduino can read it so this is where the adjustable ppr setting would come in handy.?
--
Allen ?Merrell

I'd put that fuse in the +12 line first.?
Easy to imagine supply ground having an alternate path through house wiring and RF ground rods,
vehicle sheet metal, etc.? I believe Allison once said she puts fuses on both +12v and ground,
which is more than I usually see.

Splitting it into two portions, fusing most of the rig at 0.5 Amps and the IRF510's at 3 Amps,
means you don't need a smoke inducing event within the main part of the uBitx to blow the 0.5A fuse.

I've printed this out. Something to do on a rainy day maybe?

Thanks,

tim ab0wr

On Thu, 07 Jun 2018 10:33:24 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Here's an outline of how to get dangerous with LTSpice:

Download the free LTSpice from Linear Tech:
? ??
It primarily targets the various MSoftWindows operating systems.
They also have a version out now for Mac OS-X.
Will run under linux with Wine.

Also download this
file:??/g/BITX20/files/KE7ER/ubitx_pa.asc

Kick off LTSpice.
Click File, then Open, browse for that ubitx_pa.asc file you just
downloaded. Should display a schematic of Q90 on out through the
finals for the uBitx.

Click the RunningMan menu icon (5 over from the left edge) to run the
simulation. It should open a second window to show waveforms, but the
window will be empty. Click on nodes in the schematic to see the
voltage waveform at that point. Double clicking will erase all other
waveforms and just show the last one selected. Click where wires
enter into part symbols to see currents there.

Edit part values by clicking on that value.
Edit wires by using the Scissors icon to cut away wires, then using
the Pencil icon to add new wires.? (You first have to click somewhere
in the schematic to select that window.) You can add grounds, caps,
coils, resistors and diodes by clicking on their icon in the menu
bar. Click the AND-GATE icon to explore the various other parts
available to you.

Someday, click the Help menu item, browse the destructions.

LTSpice is an incredible gift from LinearTech to the electronics
hobbyist and professional engineer. It has a full catalog of the
various LinearTech products and complete demo circuit simulation
models for each. Fortunately, it is also a first rate generic analog
simulator with an easy to use interface.

Jerry, KE7ER

On Thu, Jun 7, 2018 at 09:37 am, Jerry Gaffke wrote:

I'm not one that takes easily to new tools,?
but found LT-Spice easy to get started with.
Changes can be hacked in and checked faster than it takes for my
soldering iron to heat up.
You can easily instrument voltage, current, power dissipaton, and
much more.
It's worth a couple hours of fiddling with to get started.
I'm no expert, but let me know if you get hung up on those first
steps.

Jerry,

I've prototyped things for 55 years. It's why I like Surfboards so
much.

I might try LT-Spice someday again if I ever get any spare time.

My ubitx is built in a U-type case, a U bottom matched with a U top.
Pain in the butt to get to the bottom!

Right now I'm trying to figure out why this mmic amp is giving me 25db
gain instead of 12db. Don't know if I am measuring wrong or the
datasheet is wrong below 500mhz.

It's so doggone simple its hard to believe I am measuring wrong!

tim ab0wr

On Thu, 07 Jun 2018 09:37:57 -0700
"Jerry Gaffke via Groups.Io" <jgaffke@...> wrote:

Tim,

I'm not one that takes easily to new tools,?
but found LT-Spice easy to get started with.
Changes can be hacked in and checked faster than it takes for my
soldering iron to heat up. You can easily instrument voltage,
current, power dissipaton, and much more. It's worth a couple hours
of fiddling with to get started. I'm no expert, but let me know if
you get hung up on those first steps.

My uBitx is easily flipped over, I don't mind working on the bottom.
The (mostly) solid ground plane (mostly) ensures my new stuff doesn't
see the old stuff. And vice-versa.

Jerry, KE7ER

On Thu, Jun 7, 2018 at 09:13 am, Tim Gorman wrote:

Jerry,

One of the reasons I want to put it before Q90 is to make it easy to
access and test.

If you'll remember I was the first person on here to show spectrum
analyzer screen shots showing how the 3rd order IMD and carrier
suppression is marginal. I don't plan on doing anything less with
this amp in the chain. If Q90 distorts it should show up in 3rd
order IMD results.

I'm not much on LTSpice and that genre of software. I tried using it
once but just too many demands on my time to learn how to use it.
Easier to just measure actual results!