The Return of Pete's Simple-ceiver Plus (and a possible analog option)

Winter is approaching ladies and gentlemen, and it is time to think about radio projects.   Bob N7SUR suggested a direct conversion receiver project.  I think this is a great idea.   As a kid, I had fallen victim to the idea that building receivers was "too hard" for radio amateurs. Not true!  DC receivers to the rescue!  Carry on with the DC revolution first launched by Wes W7ZOI in 1968.

Pete N6QW is providing guidance and tribal knowledge via his blog.  For those of you who want to join the ranks of those who have defied the conventional wisdom and have broken through the "receivers are too hard" barrier.  I say build yourself a DC receiver.  Build it from scratch.  Many of you already got your feet wet in homebrewing with the Michigan Mighty Mite project.  Now it is time to jump into a DC receiver project.  

You folks already know what kind of VFO Pete will prefer:  It will be an Si5351.  That's fine.   But I will try to keep the banner of discrete component analog ludite-ism flying high.  This morning I ordered a batch of 7.37 MHz ceramic resonators.  I hope to pull them down into a significant portion of the 40 meter phone band.  If this works, I will share the batch with anyone who wants to joining my Analog Army (remember the CBLA?).   Note (above) that Pete has magnanimously left open the possibility of using a non-digital VFO. What a guy!    

Check out Pete's project here: 

http://n6qw.blogspot.com/2017/08/a-new-line-of-transceivers-difx_19.html

Pre-eclipse Solar Observation

I'm not sure if I'll be able to get a look at the eclipse tomorrow -- I'll be at work,  and in any case Washington DC will be far from the zone of totality.  But all the eclipse talk made me want to get my old 4 inch reflector telescope out today for at least one solar observation.  And yes, I know not to look through the 'scope. I projected the image onto a piece of white paper.   Notice the three large sunspots at the center of the solar disk.  Pretty cool.  

BTW, it is easy to aim the scope at the sun without endangering your eyesight.  Don't ever put your eye to an eyepiece (even on the spotting or aiming 'scope) when ole' sol is in the sky!  Instead, just look at the shadow that the scope tube is casting on the ground.  Make it circular and you will be very close to having the main tube aimed at the sun. See below.   

 I like to have the eyepiece aimed down at the ground or well above horizontal to avoid the danger of someone accidentally walking through  the powerful sunbeam coming out of the eyepiece.  You do have to be careful, especially if there are kids around. 

Building an Airplane in the Basement with Insulation Foam, Tape, Glue, Poplar...

But this one is not a model RC plane.  This kid intends to pilot this plane while actually sitting in it.  

As a parent, I must say this is really nuts.  Stick to the models Peter!  Or maybe put some goggles on the big dog and let him fly it!  

Nevertheless, this is an inspriational look at what can be built in a basement using stuff from Home Depot or Lowes.    

For more info see:
http://hackaday.com/2017/08/14/building-an-ultralight-out-of-foam-in-a-basement/#more-268614

Here's Peter's earlier Cargo Plane project:

Voltage Regulators as Audio Amplifiers - Who Knew!?

Mike KC7IT pointed out that the AF amplifier chip in my Sawdust regen receiver is actually a TL431 voltage regulator. Mike writes: "It's using the voltage reference input as audio in, and the voltage being regulated as the audio out."  It works great as an audio amplifier, and with just three terminals it is a lot easier to use than our normal LM386 or 741 chips. I'd never seen a regulator used this way.

Here's the data sheet:  http://www.ti.com/lit/gpn/tl431

And here are a couple of sites that discuss this very interesting repurposing:

http://theradioboard.com/rb/viewtopic.php?t=6733

http://techlib.com/electronics/audioamps.html#TL431

A Regen that is NOT Evil

Look at that thing.  It is already painted Juliello -- this is a very good sign.  Steve Silverman sent me one of these Sawdust Regen kits a few years ago.  I put it together this week for my nephew John Henry who is very interested in Morse and ham radio.   

This is a regen that even I can love. It is simple, small and stable.  40 meters comes booming in.

Look at the schematic.  Why haven't we used that simple three-terminal AF amp IC before?   

Get your Sawdust Gear here: https://breadboardradio.com/breadboardradio/Products.html

International Brotherhood and the BITX Rigs

Bore and Heriberto's uBITX board

Nowhere is the International Brotherhood of Electronic Wizards more evident than in the work on the rigs designed by Farhan.  With the BITXs we see rigs designed in India that are now being built and modified all over the planet. Here are just a few examples of the global collaboration currently underway:

In Italy, Giuseppe is putting a BTX40 on 20 meters and making it a dual bander: 

Hi everyone, I just completed some tests on a Bitx40 running in 20 meters band. I addes the 20 as secondary band activate when needed. I apply some mods to switch to secondary QRPLab BPF filter centered to 20 meters and removed the C91 and C92 caps to work in USB. I done some RX tests in the weekend of iaru hf contest to listen some stations Active.
Here the issues registered:
1) the 20 RX sensitivity was a bit weak compared to 40 meters. I need to increase volume. ( To receive the 20 meters the vfo run to 26 MHZ, mybe some stage suffers of poor performance in this High frequency?)
I also tryed to increase the vfo over maximum allowed by raduino, using external buffer, but no results.
Please read the issues as: work but could work better!

2) the RX was not very clean: voice acceptable, but RX of Digital mode not very stable ( probably the cause could be the vfo shift for poor tuning control. I need to add lock function in firmware ...) Or interferences for free wire of connection.

3) Sometimes when switch on or change vfo to other band or mode, the bf amplifier start a self oscillation ...Resulting in my wife's screaming (the tests were also performed during the night!)

No tests was performed at the moment in TX because i need to install the LPF for the new band.
The firmware to make the test was a modified version of 1.17.1, few temporary mods to preset the vfo b to 14 MHz USB and correct the freq. Display.

These my tests.
Giuseppe Callipo IK8YFW.

Pavel is a young fellow in Cuba who is doing great things with the Raduino software: 



Hi to all.

The code was updated, the change log is this:

v1.4Update to catch up with the features added in the Raduino v1.17.1 from Allard's code (CW SPOT and bug fixes)

• Upgraded the operations instructions
  • More user friendly version with embedded images.
  • Add instructions for the S-meter, AGC and TX-power mods details and tricks.
• Moved all images to its own folder "images".

As usual tips/bugs/comments/suggestions are welcomed, you can reach the code here: https://github.com/pavelmc/bitx40/

There is a inoffensive bug in the calibrate process, in which the actual calibrate value is not correctly showed in the LCD until you move the pot to adjust it, I'm working on it.

I'm slowly working in this direction now:

• Bug removal in the calibrate function.
• Finish the upgrade of the Si5351mcu lib with some improvements.
• Adding CAT support via ft857d lib (https://github.com/pavelmc/ft857d):
• Full compliance needs get rid of all the blocking delay() sentences and that need a structural/paradigm code change and a lot of testing (I have Fldigi/MixW/Hamlib to test, I think if that 3 works the rest will do it)
• Moving to a library (yatuli: https://github.com/pavelmc/yatuli) for the pot usage, that will ease the process of implementing the CAT as almost all delay() calls are related to pot/clicks, so I'm on it.
• Maybe implement a multiclick lib to optimize the code and make it more easy to understand.

 Any thoughts or whishes related to that?

I plan to make the CAT operation optional via a #define declaration as not all of us will/want-to use that.
73 Pavel CO7WT

Here we see Bore in Montenegro working on a uBITX designed in Cuba by OM Heriberto

Hi Colleagues

Bore Lezaic from Montenegro is working on the uBitx PCB designed by Heriberto -CM2KMK- from Havana, Cuba

Here some pictures he(Bore Lezaic) have posted in my FB wall.

Any question regarding uBitx PCB please send to Heriberto Gonzalez Mendoza at cl2kmk@frcuba.cu (please take care with the email address it is slight different to his actual call sign).
Qrv's
73's Jc

Bore and Heriberto's Board

Hidehiko in Japan was struggling with some LCD noise in his experimental BITX40.  I passed along the active filter circuit that I'd first seen in Roy Lewallen's Optimized QRP rig. 

To

BITX20@groups.io Jul 29 2017 at 4:22 AM I've finished the Bitx40 experimental project today. I added the AF-AGC and LM386 POP limitter with raduino v1.20.1 (Thanks Allard). And I also added the DuinoVOX for Digital Mode operation. It's a great radio but the problem is only the "LCD noise" when increasing the AF volume. hi... Can I reduce this noise? Or I have to use the analog VFO? Any suggestions welcome.
ja9mat Hidehiko

To Hidehiko JA9MAT: 

Very simple.  Just three parts.   NPN transistor (like a 2N3904) and a 47k resistor (collector to base) 100 uF cap (base to ground).   Vcc the collector. Emitter goes to the DC power input of the AF amplifier.  You can see my use of this circuit in the schematic in this blog post:
Look in the lower right, near the LM386 AF amplifier.  Click on the schematic to enlarge.  73  Bill N2CQR 

My Organic Chip Rig with an LTSpice Schematic

Thanks Bill,
Well I added "3-parts"(2N3904+47kohm+100uF) between the D18(1N4148) and the junction of R111(100ohm) and R1113(220ohm). The noise has absolutely gone!
ja9mat Hidehiko.

_._,_._,_

ZL2CTM's Homebrew Transceiver Project

Wow, Charlie has a lot of very cool ideas in this initial video.   Some suggestions: 

-- With the IRF-510 in the final, beef up the heatsink, and follow Farhan's lead by including an option for 24 volts on the drain.  That would take you  up to 20 watts or so (for those who are so inclined). 

-- Could that Teensy SDR board work at the IF frequency?  If so, consider putting it ahead of the crystal filter.  This would enable us all to join the Waterfall Signal Purity Police Force. 

-- I love the OLEDs too, but I found them to be noisy.  I minimized the noise with shielding around the OLED and active decoupling on the power line to the AF amplifiers.

More of Charlie's work here: 

https://plus.google.com/107506245856154702088