Category: BITX20

Farhan Visits Northern Virginia and SolderSmoke HQ

Our good friend Farhan came to Northern Virginia last week for the 50th Anniversary Symposium of AMSAT. We were really delighted that he also came to SolderSmoke HQ. Elisa and I gave him a lightning tour of Washington DC (including a quick visit to The Air and Space museum) and then we headed back to the shack from some radio work.
In the picture above you can see my BITX-20 (that Farhan designed) off his right shoulder. Off his left shoulder you sits my ET-2 rig. I really wanted to show Farhan how well the N0WVA regen performs — he was impressed, especially when we started listening to SSB contacts. It was really amazing that we were doing this with just one J-310 FET. This was great fun. Farhan tells me that he will soon take up the “two transistor challenge.”
When he was here in 2017, I tried to demonstrate my version of Rick Campbell’s R2 Direct Conversion receiver. Unfortunately, when I tried to show off the “single signal” capability that is the whole purpose for this receiver, it was NOT producing a single signal output — you could hear the signal on both sides of zero beat. One of the small AF chokes I had used had gone open, knocking our one of the two DC receivers. This time I had the problem fixed and single signal reception was successfully demonstrated.
Farhan brought me two pieces of test gear that I have needed for a long time: A step attenuator and a two tone generator. Paired with his Antuino, these devices will bring about a big increase in capability on my bench.
It was really great to have Farhan in the shack. We had a great time talking about ham radio and homebrewing. Elisa and I both really enjoyed hearing from Farhan about his travels and about his life in India. We are all really lucky to be in the same hobby as Ashhar Farhan. Thanks for the visit Farhan.
Here is a quick video of Farhan tuning the BITX 20.

Walter KA4KXX Operates his FB Al-Fresco HB Scratch-Built BITX 75 (Video)

Dear Bill N2CQR:

For your amusement, the attached video (from 2:20 – 3:40) shows
me operating portable at a tailgate event using my second
scratch-built BITX, with this one running 45W on 75M.
Features include analog VFO, a 16-pin LM380 with all ground
pins heat-sinked for powerful audio, and 3-transistor uBITX-type
low-level RF amps. The 8-crystal filter is also like the uBITX design
but at an 11 MHz IF. The microphone amp is a 741 Op Amp which I
believe has better gain, gain adjustability, and frequency response than
any of the transistor designs. The transmit adjustable driver amp is adapted from the FET
circuit used in the Wee Willy. The Transmit LPF is hard-wired to the antenna connector
for simplification and to minimize RF losses, so in receive mode the single relay in the rig
connects the receive section in parallel, which causes some signal loss, but not much.
Finally, and most notably, I believe that my RF Power Amp is the only one in the world to use
model airplane engine mufflers as heat sink cores…

72,
Walter
KA4KXX
Orlando, FL

KC1FSZ’s Peppermint III Homebrew BITX with Mods


Hi Guys:

I had some time over the holiday to finish off my second scratch-built rig. I am very thankful that I got the work done on these projects before I read Pete’s “Don’t Build It” diatribe. That would have been very demoralizing. 🙂

Scratch build #2 (called Peppermint III) is still fundamentally BITX although I’ve made changes this time around. I’ve switched to ADE-1 mixers with LO ports driven by adjustable gain buffers (ala N6QW LBS). I’ve noticed that performance can be improved a lot if you can buffer/tweak the LO levels of the VFO and BFO (particularly carrier suppression on TX). I did W7ZOI TIAs in the IF chain. I’ve also taken the shielding/layout of the finals more seriously and have been able to dial up the power a lot (I did the KB1GMX thing with cutting off the drain pin on the IRF510 and using the tab). The software is also greatly improved and now supports LSB/USB modes as well as software-driven PTT control for RTTY/FT8 and the hooks for my poor man’s panadaptor. I’ve been working lots of stations on QRO.

Total build time was about three months (half the time of #1) and the layout came out much smaller than before. I made a trip over to Williams/Sonoma after Christmas and picked up the 2018 edition of the Peppermint Bark candy tin on discount and I think I can make it all fit. More to follow …

Happy New Year and 73s,


 Bruce KC1FSZ


The Triple Scratch-Built BITX Club — Do you qualify for membership?

OK, so how many of you guys can join Steve M0KOV and me in the Triple Scratch-Built BITX Club?

Bill

Below are my three Bitx builds.

1st build.
Closely follows Farhan’s original 20m design but I soon changed the VFO for an arduino/ad9850. It was a fast, get me on the air build, it worked, but not well.
The output amp was built on a separate board as part of its exorcism.
2nd build.
This was to be my two band Hill Topper, we don’t have mountains in Yorkshire. Built with separate stages slotting into the eddystone box to save space and to help with shielding. The receiver worked very nicely, the output kept blowing irf510’s. I later found that they were a hopeless batch. Very hard to work on.

3rd build. Big is beautiful. Arduino/si5351 straight into the modulator and into the mini-circuit mixer through a driver as discussed. Norton feedback RF preamp and a ne5532/lm386 AF amp. At the moment it’s on 80m but it did start on 40m. It’s still a work in progress and I will have to sort that soldering iron band change.
73 Steve M0KOV

N2CQR Wins a Contest AGAIN!

Pete N6QW suggested I do a blog post on this.


This past weekend I dusted off my old scratch-built, all-analog, no-chips BITX20. (THREE CHEERS FOR FARHAN AND HIS BITX DESIGN!) I hooked it up to my trusty CCI .1KW (note decimal point) amplifier and my new 135 foot store-bought doublet. This all happened just as the Worked All Europe DX contest was kicking off, with lots of activity on 20. TRGHS. I was in. My contest operating style was in the category of “relaxed-casual-noncompetitive.” I took a lot of breaks. In fact there were more breaks than non-breaks. You have to pace yourself in the contest world.

My results:

8 SEPT: DF0HQ, SN7D, GM6X, DP6A, S51A, DL0HN, DB0HX, OZ5E, DJ5MW, HG7T, IK4UPB, VY2ZM, G6XX, EF1A, LZ5R, 9A5W, YP0C, F6HQP, DL7ON, HB9DQL, ON6NL, DA0WRTC, 9 SEPT: EI7M, P3X, RU1A, DP7D, SP2KPD, DL0WW.

 P3X might not count because, you see, Cyprus is considered to be in ASIA. Really?

Anyway, I ‘m assuming that I am the winner in the homebrew, discrete component , all-analog transceiver category. Woo Hoo!

The contest rig is pictured above. Before you point to the glowing numerals and cry foul, realize that the little Altoids box between the two speakers holds a San Jian frequency counter that was deliberately kept OUTSIDE the BITX box. So it is more of an outboard accessory. I can run the BITX 20 without the digital assist — I have an old fashioned non-digital dial pointer to indicate frequency. The “Low – High” switch you see switches the VFO from the low portion of the 20 meter phone band to the higher part of the band. The box below the BITX 20 holds the uBITX.

Seriously though, I was quite pleased with the performance of the doublet.

SolderSmoke #205 Solstice, Mars, Antennas, Displays, Phasing Fix, VFOs, Lexicon, MAILBAG

June 23, 2018

 SolderSmoke Podcast #205 is available:

http://soldersmoke.com/soldersmoke205.mp3

 — Summer solstice. Mars Observations. Graduations. Internships. Fathers Day.

 — Antenna Angst: Pete’s tribander and Bill’s Moxon. Insulation and resonance?

 — Pete’s work on color displays.

— Bill goes back to fix up older projects:

— Fixing the Frankenstein Phasing RX. Found an open choke!

 — Tightening up the HRO Dial.

— Achieving Juliano Criteria stability on a BITX20 VFO.

— Lexicon additions: “Scratch Built” “Hardrock Radio”

https://english.stackexchange.com/questions/39551/where-does-the-saying-made-from-scratch-originate

 — PastaPete: http://www.pastapete.com/

MAILBAG:
Bob Crane W8SX Corrspondent at FDIM
Ralph AB1OP Building LBS
Bruce KC1FSZ Digital Pot
Jason W5IPA uBITX in Juliano Blue
Rogier KJ6ETL ON THE AIR WITH A uBITX
Special thanks to Tim Walford for 25 years of Hot Iron.

Digital Pot

No, this is not some on-line mail order thing. Bruce KC1FSZ has done something that I find both amazing and horrifying: he using a “digital potentiometer” as the AF gain control in his BITX. Remember when pots were simple and pure, when they were just a metal wiper that ran across a crescent of carbon of increasing resistance? Well, those happy days are apparently behind us my friends. What now? Will we have endless discussions about where to find the driver for the 10k pot? Will Facebook or Amazon or Microsoft secretly seize control of the data on our AF gain, perhaps to sell us hearing aids? But enough of my ludism. Good going Bruce. AGC beckons.

Hi:

I’ve built a few BITX rigs from scratch now and I’m starting to move to a modular approach using fabricated PCBs to make it easier/faster to build/mix/match the stages. My audio amplifier module is based on the LM386. I know others have moved away from this chip, but it still works for me.

I’ve added one feature to my audio amp stage that opens up some good possibilities. Instead of the traditional potentiometer between the AF preamp and the LM386, I’ve inserted a digital potentiometer (MCP4131-103) that is controlled by three extra pins on the microcontroller. The digital pot lists for $0.81 on Mouser so it’s no more expensive than a physical pot and it’s way more versatile.

Why do this?

  • The module is quick to make if you’re building a lot of rigs.
  • AF gain can be controlled via the CAT port.
  • AGC control can be done in software. This enables all kinds of fancy AGC “attack” and “release” controls that can be seen in the docs for commercial rigs.
  • This is an enabling feature for remote ops, which is why I did this in the first place.
  • AF gain can be controlled using the same encoder (different mode) as is used to control frequency, etc. if you wanted to build a more compact rig.

The board is shown below. This is one of my first forays into KiCAD/PCBs/etc. so it’s probably not as “tight” as it could be. Also, I’m using through-hole components so it’s old-school building. But the board only costs $7 on OSHPark and it’s pretty quick to wire up. Anyone who wants to order one from them drop me a line and I’ll send you the link.

Schematic below.

73s,
Bruce KC1FSZ


KC1FSZ’s Above Board, Al Fresco, Free Range, QRO, 4-Foot-Long, Wood-Based BITX

DON’T BOX IT UP BRUCE! LET THAT RIG LIVE FREE AND BREATHE!

COULD THIS BE THE WORLD’S BIGGEST BITX?
Hi Guys:

First off, congrats on back-to-back SPRAT covers.

I’ve succeeded in my QRO quest. Now I’m running the finals from 28V using a home-brew linear power supply and getting about 20W out. LM723 + 2N3055’s. I’m making a lot more contacts too. The only problem is that the “Peppermint Line” is close to 4 feet long now! (Photo below). I don’t know how N6QW gets his rigs packed into such small cases. Putting the various boards in edge-wise will probably help a lot, so that’s going to be my approach to the final packaging job.

73s,

Bruce KC1FSZ

HB2HB QSO with KC1FSZ and his Al Fresco Scratch-built BITX

I had some good luck on the ham bands last weekend. First, I was called by Bruce KC1FSZ — this time he was on his Al Fresco scratch-built BITX-on-a-board. FB. The next day, I called CQ on what seemed like an empty 17 meter band. I heard someone come back — it sounded like DX. I had to swing the Moxon a bit — oddly, I thought, to the south-east. FR5FC was calling me from Reunion Island. TRGHS.

Here’s a follow-up message from Bruce:

Hi Bill:


Great to catch up with you on 40m yesterday. I was using the Peppermint II which is a scratch-build of the BITX-40 for the most part, although I did my own digital VFO/BFO and made a few other modifications in order to be able to use it on 80m. It took about 8 months of noodling to get the thing to work, but it was a great learning experience.

As discussed, I’m working on a 24V power supply (LM723 + 2N3055) and a push-pull IRF510 final so that I can get some more power.

I got a few more Williams-Sonoma Peppermint Bark tins off of EBay so I’m ready to start boxing things up as soon as the linear is working.

73s,

Bruce KC1FSZ

Termination Insensitive Amp Boards from VU3ZMV — Eagle Files

Bill:


Here are the eagle file data for the TIA, that I love to use as incorporated in Farhan’s ubitx.

 The TIA , I tried to realise two such on a double sided pcb measuring less than an inch.

It mounts one TIA on each side. I suppose one could simply homebrew.

It has provision for 5 pin berg (male right angle) and would be easy to plug into the main board. We may not need PTH except the connector. We can use bare pins soldering on either side.

Here are the eagle files I created.

Termination Insensitive Amp Boards from VU3ZMV — Eagle Files

Bill:


Here are the eagle file data for the TIA, that I love to use as incorporated in Farhan’s ubitx.

 The TIA , I tried to realise two such on a double sided pcb measuring less than an inch.

It mounts one TIA on each side. I suppose one could simply homebrew.

It has provision for 5 pin berg (male right angle) and would be easy to plug into the main board. We may not need PTH except the connector. We can use bare pins soldering on either side.

Here are the eagle files I created.

Another Source for BITX Amp Boards – AG4ZP

Thanks for sharing (the infor on the modular BITX boards). I actually had a similar idea a number of years ago and designed a small PCB for the ubiquitous BITX amplifier design. I have the project shared on OSH Park and you can get three of them shipped for $5.

The project is shared here.
73,
Ryan AG4ZP

 https://oshpark.com/shared_projects/6mnfQQ6e

Modular BITX Boards

AE7KI (VK2APG), FT8, and WAS on a BITX20

I’ve had several very nice conversations with Gerry AE7KI (aka VK2APG). His Australian accent sets him apart from the other Tennessee stations. Last time we talked Gerry mentioned having competed Worked All States with his BITX20 (below). Very cool.
Gerry also alerted me to a new digital mode created by Joe Taylor. This one is called FT8. Gerry is using it to good effect on the 6 meter band. Here is Peter Marks’ initial reaction to FT8:

http://blog.marxy.org/2017/07/new-weak-signal-mode-ft8.html

As I type, there are 252 stations monitoring 6 meters for FT8 signals. You can see a map displaying these stations here:

https://pskreporter.info/pskmap.html

Put Yourself on the BITX Map


On Jun 9, 2017, at 4:53 PM, Doug W wrote:


Seeing the topics for regional operator lists got me thinking. If words are good, pictures are better. I set up a google map that you can add yourself too to help visualize where everyone is located. I was going to add people that responded to the other topics but out of respect for privacy (and my laziness) this should be entirely opt in only. The map is only accessible with the link below. The interface is reasonably intuitive but I will do my best to explain how to add yourself.

go to

https://drive.google.com/open?id=1Oa_egVdStSJBF5C7mpS6MXrkces&usp=sharing

type your address in the search bar on the top of the map (the box with the magnifying glass to the right)

hit enter or click the magnifying glass
verify the location displayed
click add to map at the bottom of the box that pops up
now click the pencil/edit icon at the bottom right of the box
change the highlighted address to your call sign and click save at the bottom left of the box
you can also add more information to your spot if you choose to
bookmark the link and check back as more people add themselves

I am making this sound much more complicated than it is. If anyone can describe the process better please do.

Indonesian BITX: Check out the BRITX

Pretty cool, don’t you think?

Here is the Google translation of the “about” portion of OM Dian Kurniawan’s blog:

Electronics is something very interesting. In it are stored many miracles of His creation. The almost limitless opportunities for creativity make electronics an art medium. Countless things are ultimately made easy and possible with electronics…. Feel free to start. Life starts from a cell. Let’s keep working for a better life. Salam.

It is obvious that OM Dian has THE KNACK and is a member of the International Brotherhood of Electronic Wizards. Does anyone know his callsign?

There is a lot of very cool stuff on his blog, including some mind-blowing applications of small, color displays. Check it all out:

https://diankurniawan.wordpress.com/


Indonesian BITX: Check out the BRITX

Pretty cool, don’t you think?

Here is the Google translation of the “about” portion of OM Dian Kurniawan’s blog:

Electronics is something very interesting. In it are stored many miracles of His creation. The almost limitless opportunities for creativity make electronics an art medium. Countless things are ultimately made easy and possible with electronics…. Feel free to start. Life starts from a cell. Let’s keep working for a better life. Salam.

It is obvious that OM Dian has THE KNACK and is a member of the International Brotherhood of Electronic Wizards. Does anyone know his callsign?

There is a lot of very cool stuff on his blog, including some mind-blowing applications of small, color displays. Check it all out:

https://diankurniawan.wordpress.com/


Homebrew Peppermint BITX: KC1FSZ Goes Scratch-built and Sweeps a Filter

Hi Bill/Pete:


Congratulations to Bill on the award. Very well deserved!

I just watched the video that Bill made with Farhan and I really enjoyed it. As usual, lots of useful information there.

Farhan’s demo of the Sweeperino was particularly timely because this past weekend I was doing something very similar.

As I’ve mentioned to Bill before, I am working on a scratch-built BITX to accompany the Peppermint BITX-40 module rig that I’m running right now. I took Pete’s advice and started from the audio end. After building the audio amplifier, product detector, and first/last pair of IF amplifiers, I was able to connect the VFO where the BFO is supposed to go and enjoy a pretty reasonable direct conversion receiver. It works great!! My first working receiver.

So my next step was the crystal filter. I puzzled over all of the different articles, tried to follow the G3UUR method, sorted crystals, etc. and finally put the whole thing together. But all along I’ve had this doubt that I could have possibly followed all of the steps closely enough to achieve the precision needed for a 3.5 KC SSB filter – it just didn’t seem possible.

Last week I decided to try to “sweep” the filter. This was a multi-day undertaking in itself. I pieced together the microprocessor, an AD9850, a TIA amplifier, the RF power detector from the SSDRA book, and some software that generates the necessary frequency sweep and collects power readings. The picture of the test rig is included below. It’s not much to look at.

With low expectations (and wires that are too long), I ran a few seeps and then downloaded the data onto my computer for analysis. No fancy software here, I’m just using Excel. When I put the data into a line chart in Excel, what emerged from the jumble of seemingly random numbers was a thing of beauty: a 3.5 KC passband right below 12 MHz. It’s the next stage beyond the Joy of Oscillation: The Joy Of Selectivity!


It’s even showing about the right insertion loss. Note the setup is very primitive and noisy so the fact that I can’t measure anything below -8dB isn’t surprising, you can ignore that part.

But I’m starting to get the feeling that this might actually work. Onto the diode mixer …

73s,