Thursday, August 31, 2017

Ergonomic BITX Enclosure -- 3D Print

Wow, Michael's amazingly cool BITX enclosure looks like you could use it to ask Scottie to beam you up. 
Put an end to those freakish contortions -- 3D print yourself an Ergonomic BITX box! Very FB Michael. Thanks. 

Hi Bill and Pete:

I thought you’d be interested to see my ergonomic enclosure for the BITX40. While operating homebrewed regen radios, I noticed that my hands/arms/shoulders were becoming uncomfortable after a while. After thinking about this for a few days, I realized that the dials on the front of these small radios were forcing my hands into freakish contortions—and having both hands on the dials at all times while tuning made matters worster faster! So I did some homework and determined that our arms and hands most naturally hold things toward each other, as though they are holding a small cylinder by the ends. But the conventional “dials-and-speaker-facing-front” radio case forces us to twist our hands up and outwards from our bodies to twist things. See my blog post for illustrations of this problem.

My enclosure design for the BITX40 re-orients the volume and tuning knobs toward the sides of the radio, making their operation much more natural—and pleasant. Although it’s not retro, it does have an unconventional appearance and should fit in quite naturally with all the other homebrewed solutions featured on SolderSmoke. 

You can visit my post at; the box is available for download and printing at Thingiverse:

By the way, I also have a 3D printable mic for the BITX40:

73, Michael VE1LEB

Saturday, August 26, 2017

Speech Processor and Antenna Tuner/SWR meter for BITX

Check out the blog of homebrew wizard K.P.S. Kang.   OM has a nice speech processor based on the LM386.   He also has a very simple antenna tuner and SWR bridge.  FB OM.

Monday, July 24, 2017

KC8WBK's Cakepan BITX Enclosure and PVC Mic/PTT Grip

I talked to Paul KC8WBK last night during the regular 7277 kHz Sunday night BITX gathering (7 pm local). I like his BITX enclosure.  Very practical and economical.  It provides ready access to the circuitry.  He also has nice enclosure for the microphone and push-to-talk switch. He has more info on his page. 

Thursday, June 1, 2017

KY3R's Metalized Cigar Box BITX Enclosure

Bob KY3R writes:

Bill:  I was watching your visit with Farhan, and you mentioned your penchant for building projects into wooden hobby boxes, and using copper  flashing for shielding. I want to share my solution. 

I snatched up any old cigar boxes I come across. For shielding I use "metal repair tape." This is the stuff used for joining or repairing dryer lint vent ducts, and it is available at any hardware store. Very lightweight, and you just cut the desired lengths, peel off the backing, and press onto the inside of the box. The only drawback is that it is aluminum and doesn't take solder very well, but it is easy enough to add one or two short lengths of wire from the circuit ground plane to a terminal bolted down onto the case interior. 

The attached photos show my current project--a Por Larranaga cigar box in the process of being converted into a home for a BitX-40! I haven't yet fully decided exactly how to position the unit in the box, but as shown in one of the potos, it fits with plenty of room for later mods. As for other decisions, I toyed with the idea of painting or covering the outer box, but I am leasing toward leaving the original cigar box labeling. Arguable adds a bit of "soul," plus who needs a clean panel and all that fancy stenciled lettering anyway.I'll know which knob is which! <g>

73, and as always, thanks to you (and Pete, of course) for your continued work on the SolderSmoke  podcast.

Bob Keller, KY3R

Thursday, April 6, 2017

Hot Water BITX 40 Hack

Fred's idea really resonated with me.   My first SSB rig was an HW-32A, the 20 meter version of the rig shown above.  If -- as I suspect -- these rigs are anything like the HW-101, they are not aging well. Heath's drive for economy resulted in rigs that don't hold up to well over time. I remember the sound of the  plastic HW-101 dial clutch cracking when I pushed the button.

BITX40 Modules to the rescue! Put a mono-band board inside an old mono-band rig.   There are a lot of possibility here.  Some ideas:

-- Put that Heath VFO to use.  Maybe convert it to solid state.  Or just put the LCD from an Si5351 in the window (Pete did this with an HW-101).

-- Get the S-Meter wiggling.  

-- Keep the final amplifier circuitry in there and let the BITX drive it.  This will give you a QRO option.  Bill N2CQR 

Hello Fellows,
Attached is a picture of my BITX-40 V3 adapted to a Heath kit Single Bander HW22. This is a work in progress but what a neat way to bring an old boat anchor into the present.
The only parts of the HW 22 used were the front panel and case and knobs. Modifications yet to be  incorporated include: AGC , a USB port on the front panel to access the Arduino, and a PTT/CW mode switch.
I enjoy your pod cast and web site…Best of 73 KC5RT.

Wednesday, March 29, 2017

ND6T's Forward and Reverse Power Meter for the BITX

RF Monitor
by Don Cantrell, ND6T

In response to several requests for a VSWR and output power monitor I have developed a simple circuit to be easily added to the BITX (or any transceiver) and some software to get it working. I used a 20 dB directional coupler design, sometimes called a “Stockton bridge”, that is simple, broadband, and requires no adjustment.

The sensor circuitry is mounted on a small piece of printed circuit board that is held in place under the mounting nut of the BNC antenna connector, replacing the ground lug that was originally supplied. The (brown) wire from the 2-conductor “ANT1” plug feeds through the center of one toroid core (T1) and solders to the BNC jack, the other (black) solders to the new board's ground plane. Two new wires connect to the Raduino plug for reading and display of the results.

I began with a square of un-etched printed circuit board stock, one inch on each side, and drilled a 3/8” hole near one corner to fit over the antenna jack. Leaving enough room for the mounting nut, I glued 4 small pieces of PC board as solder pads. The two transformers are T37-43 ferrite cores wrapped with 10 turns of AWG#24 wire in a single layer. The 50 ohm terminations are ½ watt 51 ohm resistors. I hand-selected two of the ones closest to 50 ohms but this is not critical (what's an ohm between friends?) ¼ watt will work fine at these levels. I used two 1N34A diodes for detectors.

I mounted all of the components upright to save space. A short jumper wire feeds from T1 secondary through the center of T2 to the forward detector as that primary winding. Note that you do not wrap this around the core, just pass it through like the antenna lead on T1.

Don't have any #24 wire? Use whatever you have that will fit 10 turns. Don't have a T37 core? A T50 or even T60 will work. It is best, however, to stick to 43 mix ferrite unless you adjust the turns accordingly. Capacitor voltage or temperature coefficient is not important. Got lots of room around the antenna connection on your build? Then go large with the PC board and give yourself some space for component mounting and ease of connection.

Testing is simple. If windings have the proper polarity then, when you transmit into a dummy load, there should be a couple of volts DC on the “Forward” solder point and a very low voltage on the “Reflected” pad. The coupler works the same in both directions, meaning that if it were built outside of the BITX, then you could reverse it and get the same readings by switching voltage pads. A nice check of operations. 7 watts on my build resulted in a bit over 2 volts volts on the output, well under the maximum 5 volts allowed on an Arduino® A/D input.

I included some formulas in the software to average the peaks during SSB operation and displaying it every 3 seconds. The results are also displayed after a half-second key down in straight-key mode. The power reads out as watts in both forward and reverse directions. As usual, the Arduino sketches are available free by emailing

Not using a digital readout? Just attach meters and adjustment pots to the output connections. If you want just one single-movement meter then use a switch and a trim pot for each switch position.

de ND6T

Tuesday, March 28, 2017


BITX CW Update
By Don Cantrell, ND6T

Since the last post (February 25, 2017 “Putting the BITX Raduino on CW”) I have made a few changes in the sketches, added a variable keying speed control, and added a Straight Key mode. In the ensuing weeks it has performed nicely on the air, superb reports from everyone.

The primary reason for the initial sluggishness in calling up the original keying routine was that the display updating necessitated a sizable delay to keep it from flickering. By moving the display update out of the loop() and putting the CW into a “while()” structure made the delay essentially disappear. It also cleaned up the code, modularizing it to make it easier to re-configure and to steal whole sections to use in other sketches. I decided to use iteration counts (how many times the subroutine ran) to create the time-out to return from CW transmit to receive. This is called “semi-break in” operation and is used on many rigs. This is still primarily a 'phone rig, after all. I was reminded about how fast the Arduino works by the number of iterations it performed in 1.5 seconds...100,000! Zoom! Yes, it read the paddle inputs 100,000 times in one and a half seconds.

The next big change was a speed control. I am not a fan of menus. I want to turn a knob and go. So I drilled another hole in the front panel of the BITX and mounted another 10K linear taper pot. I wired it like the tuning control: +5 volts to one side, chassis ground to the other, and the wiper to an unused A/D pin on the Raduino. Since the new speed control was right near the tuning control, I just wired from that for the end connectors.

The CW function reads the value and converts directly to Words Per Minute. The display shows the two-digit speed at the end of line 1 right after the “Idle” indicator on my program. I have it set for 10 to 35 WPM, pretty much my normal range. It can be changed to cover whatever range the operator would like by a couple of simple changes in the code. That code is still extremely short, small, and in simple Arduino.

I am not a person that shuns Straight Key mode, though. In fact, I rather prefer it. It is simple, understandable, and has character. Much like a persons' hand-written messages. An operator's fist is as distinctive as his call. And who can send CW slower than 10 WPM on a paddle?

With the current sketch, turning the keyer speed control to less than 10 WPM replaces the speed indication with “SK” and directs the program flow to the straight key function. Again, after 1.5 seconds of no key closure, the BITX returns to receive.

The only glitch occurs if the straight key uses a 2-conductor plug or has the sleeve and ring conductors shorted and is plugged into the 3-conductor key jack. Do that and the Raduino sees it as a request for a “dash” from paddle. This is handled by reading the speed control. If the control is set for “SK” then all is well. Leave it on a keyer speed position with such a straight key plugged in then you can expect the BITX to start transmitting “ DAH DAH DAH...” until you realize your error.

Although I was initially worried about key clicks due to the fast rise time of the keying envelope I don't see much difference from my other CW rigs. My Icom 746pro is not bothered just 100 Hz away from the 50dB over S9 signal when using a 50Hz receive filter. No one I have worked notices a problem. One operator using my conversion thought it had some chirp but it turned out to be receiver overload instead. Not the BITX, another receiver, relax.

Dmitry, EI3JQ, reported that he had to use a lower value series resistor at the signal injection point at C132. He says that the 470 ohm resistor resulted in low output. Further reports are still pending but I expect that different builds will show variation. It is my opinion that the CW output should be no more than the SSB PEP level to maintain signal purity and lessen component strain. The average power difference is nearly 10 dB and should be taken into account. Dmitry had much lower power, though. He reports nice CW contacts both in Europe and Russia now.

I also re-wrote the sketches to reduce the number of synthesizer and display refreshes. The newer versions of the etherkit Si5351 libraries ( v 2.0.2  and v 2.0.3) shut off the synthesizer outputs for a brief time when programmed for frequency. This creates a clicking in the audio. My earlier sketches were constantly updating so it was particularly irritating. Jerry, N5KYD, found this problem. I suggest using v 2.0.1 until the library is further corrected but my newer sketches have profitted from the experience.

If anyone wants a copy of the current sketch with CW, for either the 40m Raduino BITX or the 60 meter version, just write me at: ND6T@ARRL.NET  for a copy. There are changes made almost daily, lots to improve. The fun is in the innovation, after all!

de ND6T