Author: Peter Marks

Ken G4IIB’s BITX Journey

The work of Ken G4IIB has been on this blog before — he helped many of us make use of the amazing RTL-SDR Dongle SDR receivers. He has recently turned his attention to the BITX40 Module and offers some great ideas for testing and for modification. Ken’s description of the smoothness of his audio adds a very evocative term to the SolderSmoke Enhanced SSB lexicon.

Hi Bill, Pete

Many thanks for your respective responses to my plea for help in setting up SI5351 derived BFO to my BITX40 board. You were both on the money.


Pete suggested that I had too much gain in my HB amplifier from the SI5351 output to the modulator and indeed that proved to be true. Once sorted I also noted that I was getting extra hiss on switching to one of the sidebands as you pointed out Bill this proved to be due to incorrect placement of that particular BFO frequency.

These BITX40 boards that Ash Farhan has developed and released to the world wide community of Radio Amateurs are worth every penny. Because they are so hackable (not just the circuitry but now the Raduino code also) it means that you can tailor it to your specific specification and in the process you are likely to learn new stuff and make new friends. I describe my BITX40 incarnation and experiences below:

Upon first firing up the BITX I was getting quite a lot of mains hum from my PSU’s (I thought that at least one of these PSU’s was a quality item) but obviously not up to the job. I constructed a simple one transistor capacitor multiplier (this converted a humble 1000uF cap into a 1F cap) and the noise magically disappeared. By coincidence I note that Bill discussed this technique in a recent pod cast. Another advantage of this technique was that I got a 2V drop across the transistor so by running this on 13.8V I get 12V out so I run the PA section on un-smoothed 13.8V (this gives me 12 watts of RF out) and run the receiver section on the smoothed 12V output from the multiplier, happy days.

My thoughts were to turn my BITX into a multi band (several bands rather than all bands) rig and I figured that using high side mixing (running the VFO at 19Mhz (12Mhz + 7 Mhz) rather than the existing low side mixing (12Mhz – 7Mhz=5Mhz VFO)) would be a better option. For example running it on 17M would mean using high side VFO anyway. I also wanted the ability to be able to switch sidebands especially on the lower frequencies so that I could use the rig for Digital modes in my case this was to be achieved by coding the Arduino to run a BFO on one of the SI5351’s clk ports.

I bought my BITX prior to the release of the Raduino so I had already commenced (with the aid of a new found radio friend and RF mentor) coding an Arduino VFO/BFO using a UNO and SI5351. Like I said at the beginning once you let folk know that you are starting on a new and interesting project you start to engage the more practical members of the ham community and they just want to get involved and help. Yet another good reason to buy a BITX . We used code originally developed by Jason Mildrum NT7S and Przemek Sadowski SQ9NJE and tailored it to suit the BITX40 and our requirements. This include high side VFO with frequency step adjustment and a BFO with long push BFO changeover. This meant that my BITX front panel should stay very minimalistic 2 knobs.
Getting the VFO to work was simple as the DDS socket was used and to better accommodate the high side VFO I modified the board by tombstoning caps C91 & C92.

Getting the BFO to work proved to be more problematic I was troubled with hiss and other noise. Words of wisdom from Pete Juliano when asked if I was doing something wrong were: ” No –it is just that we tend to think our projects are like Lego type building blocks where everything mates and snaps together. Sometimes more is required”. True Pete and that gives us the opportunity to learn new stuff!

To cut a long story short I found that the best place to connect the BFO was on the modulation transformer T4 thus bypassing the BITX BFO stage altogether. I was also getting hash noise believed to be emanating from the Uno. At this stage my after market Raduino arrived from India. I fired this up and noticed that I was not getting any hash noise from it. This pointed us to a coding problem and the LCD refresh was altered on our code and the problem disappeared. Below a picture of the module showing the BFO connections to T4 and the large heat-sink with the IRF510 insulated from it. Also shown is the capacitor multiplier and a glimpse of the Raduino in the foreground. Not the most elegant box but this is likely to change pending further refinements. It’s still work in progress and this box gives me plenty of room.

The Raduino is a fantastic piece of kit for the money extremely neat and well thought out. The coding is comprehensive and innovative and works well. However, from an aesthetic and ergonomic point of view there were a few things that I personally did not like in terms of how it operates and performs. I could not get away with the potentiometer tuning, you can tune 50Khz of the band and then when you near the pot edge it increments/decrements and you can re-tune. I found this clunky to use and in addition the Raduino would hunt causing the last digit to increment then decrement causing an annoying warble on audio. In my opinion a Rotary Encoder would be better solution. On the plus side, although not mentioned on the Hfsigs web site the Raduino code does come with other functions such as changing sidebands by temporary high siding the mixer, a RIT, VFO B and CW tone. If you download and read the Raduino code from Github you will see this extra functionality which I believe you can make use of via extra switches (not supplied). The current Raduino code does not have any external BFO options as said it relies on the crystal BFO and temporally high siding the VFO to change from LSB to USB on 7Mhz.

The Raduino module itself is just too good and neat not to use. As I did not have the where for all to fully understand and amend Ash’s code I decided to use the Raduino but to load it with the code that we have developed for he Uno and Addafruit SI5351 board. This would give me near conventional tuning via a rotary encoder, adjustable step sizes via quick push of the encoder switch and USB/ LSB switching via long push of the encoder switch by virtue of the SI5351 generating the BFO frequency. I have retained a copy of Ash’s Raduino code just in case I wish to revert to it. I put a new header on the Raduino P3 connector so that I could connect a rotary encoder and use the 2nd clock output and then changed our code to run on a Nano. I had to add a correction factor in the code to cater for calibration differences in the SI5351’s (in my case 1.21Khz).

As previously indicated I had a little trouble arriving at the correct BFO frequencies I found that 119940 and 119970 gave me LSB and USB respectively for my high side VFO (19Mhz) if you use low side VFO (5Mhz) then these would be reversed. We further refined these frequencies by injecting white noise into the mic amp and looked at each transmitted sideband on my RTL-SDR dongle via HDSDR (a useful piece of test equipment). By adjusting the carrier trimmer to show the carrier in the extended HDSDR spectrum display we could see how much to move the BFO frequency to best occupy the crystal filter pass band, see image below. This frequency adjustment being achieved by a coding change. The frequencies I consolidated on to cater for my particular crystal filter are 119941 LSB and 119969 USB. We then nulled the carrier back out. My audio is now as smooth as a maiden’s inner thigh, trust me the image will follow!

So now I can get on and build an AGC and think about some sort of S meter. As for putting the BITX on other bands, whilst I now have a VFO capable of going anywhere, I would need to address band pass and low pass filter and switching arrangements. I may still experiment with this but, as pointed out by Ash in a recent pod-cast, the BITX single superhet design is not best suited to multi band operation but can be quite easily changed to operate on another single band. He also indicated that he was developing a dual superhet with consideration for multi band operation. Once released this might be a better option for multi-band use.

In the mean time folk should just get a BITX40, hack it to bits and share with us their customised versions.

Ken G4IIB


VK2EMU’s Biscuit-Tin Direct Conversion Receiver


Bill and Pete:
First Sound
The enclosure came first, then the radio. The Homebrew challenge – build something in a Christmas Biscuit tin – only one rule, no mains power.
Step one – eat the contents.
VK2WI is an Australian version of W1AW and transmits weekly new bulletins on a number of bands from 160m to 23cm. On 80m the frequency is 3595kHz, so let’s build a DC receiver for that.
I used a 7190kHz crystal, divided by 2 with a 74HC74 to get 3595kHz. The rest of the radio is pretty standard – double tuned front end, NE612 mixer, followed by a TL071 and a LM386. The reduction drive on the tuning cap gives a band spread of about +/- 300Hz.

The boards are all 2 inch x 2 inch and made on a PCB mill that I was given a few years ago.
There should be enough room in the bottom of the tin a pack of 8 C cells to make the radio truly portable. Next step is to fit an audio low pass filter.
It is a pleasure to sit on the rear porch and listen to the Sunday night broadcast on a home brewed radio, while eating the contents of another identical tin – I wonder what I will do with that one?

73 Peter VK2EMU



VK3YE’s GREAT “QRP by the Bay” Event

Last weekend Homebrew Hero Peter Parker VK3YE hosted another of his amazing twice-yearly QRP events. It was at a park near the iconic Chelsea Pier in Melbourne. Peter Marks VK2TPM sent a very nice write-up with pictures:

http://blog.marxy.org/2017/02/qrp-by-bay.html

 And a nice audio report:

http://s3.marxy.org.s3.amazonaws.com/audio/QRP_By_the_Bay_2017.wav

 Peter Marks reports that most of the on-the-air activity was on the 120 foot ham band (40 meters for you modernists). Many BITX40’s were on display.

ZL1UEM’S Tiny OLED Si5351 Arduino VFO


Hugh ZL1UEM has come up with a very creative way to take maximum advantage of the small size of the Si5351 board, the Arduino, and the OLED display. He even has the rotary encoder in there. Look carefully — he uses both sides of the board. Very nice. Thanks Hugh!

Hi Bill,

First let me say that I have been an avid follower of the SS blog and podcasts since the days of your podcasts involving Mike KL7R.

Like many others I was tempted to purchase the $49 surface mount module from HF Signals. As a keen home brewer I felt guilty about employing a prebuilt board but excused my decision on the grounds that I would build a DDS and other accessories myself.

In addition to follow the SS blog I also check Pete’s blog regularly and was excited by his OLED VFO for the Bitx40.

I constructed it on a small double sided matrix board with plated through holes. A bit of noodling led to the layout shown in the photos. There is only one board with components mounted on both sides. The board came to life on the first power up but the text spilled off the bottom of the display.

I assumed that the sketch that I had downloaded from Pete’s blog was for a different OLED module. I knew that he had also used a yellow/blue OLED, the same as mine, previously so emailed him requesting a sketch for this OLED.

I was taken aback when he informed me that the sketch I had was the same for both the dual colour OLED and the black and white one too. Pete suggested that I swot up on the use of OLEDs generally and that perhaps I should first experiment with the text size to begin with. He also offered some advice about the mapping of the screen.

I soon discovered that the text size was not the cause of my grief and that I needed to look elsewhere.

I first tried running the ssd1306_128x64_I2c sketch from the sample sketch folder and was rewarded with the message “Height incorrect, please fix Adafruit _SSD1306.h”. A search of the Internet revealed that I needed to edit the .h file and find “#define SSD1306_128_64” which was commented out and uncomment it and make sure that the other two options, _32 and _16, were commented out.

My next problem was how to edit the specified .h file. I tried notepad but the text all ran together. Another internet search revealed that Notepad++ was a suitable choice and it did indeed cut the mustard.

A reload of the sketch completely restored the display to full functionality.

All this may be obvious to many but it was all new to me and if I had not been prompted by Pete l would not have had learnt so much and would not have had the same sense of achievement when it all came together.

Many thanks to you and Pete for providing a focus for my hobby.

73’s
Hugh ZL1UEM

Schematic for the RTL SDR Dongle Front End

Here it is. Very simple. I used an obsolete 40673 dual gate MOSFET. I didn’t need both gates so I just soldered them together. You could probably substitute an easily obtained MPF-102 JFET. The capacitors and the coil in in the gate circuit form a parallel LC filter circuit that resonates in the 40 meter ham band. The 1 Megohm resistor maintains a very high impedance for the LC circuit, helping to maintain circuit Q (sharp response). It also drains off any charge that builds up on the gates. For the antenna input I just put 2 turns on the 4.5uH coil — this too helps maintain LC filter response. The 470 ohm resistor serves as the load and limits quiescent current through the MOSFET. It should pull about 19 milliamps — with a 9V battery that should give you around 26 hours of listening time between battery changes. That’s fine with me — I don’t use this thing that much.

Realize that I’m using this with an RTL-SDR dongle that has been given the familiar modification that allows it to use direct sampling in the HF bands. Some ideas here:
and here
and here

Adding a Homebrew Front End to an RTL-SDR HDSDR Receiver

I started playing with the RTL SDR dongles again. I wanted to use them to confirm that my BITX signal is NOT 9 kc wide (it is not). I also wanted to try to confirm the aircraft band frequencies in use in this area.

So I got the HDSDR software running and plugged in the dongle that I had modified for HF use. It worked great, but I could see (literally SEE) that it needed some bandpass filtering and perhaps a bit of RF gain. So today I threw together this device. Dual gate MOSFET (gates tied together) with an LC filter on the gate. Power from Malaysia via the 9V battery.

It works great. It was fun to add a bit of homebrew to an otherwise soul-less commercial receiver. But beware: that waterfall is addictive, even for a hardcore Hardware Defined Radio guy like me.

“First Light” on Brad’s Direct Conversion Receiver

So cool. You can just feel the enthusiasm. Congratulations Brad!

Bill and Pete:

After 63 years, I was finally able to build a DC receiver of my own design. We achieved “first light” at 7:20P last night. I attached the antenna, speaker, then applied power – and a all of a sudden “Bob’s your uncle!!” There are some things I still don’t quite understand but right now none of that matters as I listen to the sound of clean, crisp CW pouring out of the speaker and filling the room!! Major components – SI5351, SBL-1, TL072 op amp bandwidth filter, LM386 audio amp. I plan to use clk2 of the SI5351 with some Arduino code to create the companion transmitter and CW keyer. Life is good!!!
Brad WA8WDQ

W8LM’s BITX on a Board

The purpose of the BITX40 project was to encourage modification, experimentation, and more frequent melting of solder. I think these pictures from W8LM serve as yet another reminder that this goal is being achieved. The contrast with the big appliance rig in the background is, in so many ways, striking. You’d be understandably reluctant to take a soldering iron to the commercial rig, but the BITX seems to be crying out for hot iron and solder smoke.

W8LM wrote (on the BITX20 group):

Guys- Here are pix’s of my BITX40 fired up today in Receive for testing. #1 I have the tuning clicks- so I will be debugging that. #2 shown in the pictures is my test of calibration which was not necessary. I used a T and put my ICOM 756proII and the BITX40 on the same antenna (a Windom flat top at 33Ft) The display of both read 7.1700 pretty much the center of the band and I was copying 4’s,8’s and 2’s at 23:30zulu) By moving volume controls up and down I could listen to both rigs same frequency, audio comparison acceptable. An AGC circuit is in order. The mylar-plastic cone of the surplus speaker lacks fidelity. Unfortunately the 16×2 display did photograph well. It’s a start– de W8LM

A Mighty Mite, a BITX40, an ILER, some Arduinos, and the Joy of Oscillation in the United Arab Emirates

Martin A65DC sent us this wonderful report on his efforts in the UAE. His e-mail nicely conveys his enthusiasm. I was especially pleased to see that wooden enclosures are catching on (another fellow on the BITX20 group is using a cigar humidor). Thanks Martin! Please keep us posted on your UAE homebrew adventures.

Hi Bill and Pete,


My name is Martin, and I am listening to every episode, sometimes more than once, thank you for an excellent show boys. I am a ham in the United Arab Emirates and operate radio as A65DC.

I just wanted to share my “JOY OF OSCILLATION” moment with you, I had the moment two days or so ago.. fantastic!

Well it is not super tidy, but as a proof of concept is totally acceptable. red and green goes to the variable cap (above).
Next to the Mighty Mite (above) is my bitX40, what a fantastic board!! I have big plans for this radio. But for now it will stay in its wooden box and keeps me company.
This (above) is another kit build, 20m SSB kit from EA3GCY Javier. ILER20, please have a look, this is where you should start if you are into kit building!! the instructions are fantastic.
I added some Arduino magic to it with a SI5351, and then I was sitting and looking at my big UNO board, hmmm USB port, why not further develop the code and use the port as CAT control.
I can now connect this rig to e.g. N1MM and control it, read and write frequency (in current version) I am simulating the protocol of a TS590, but that turned out to be a bad choice, I should have gone for a simpler radio, like a 140 or something, the 590 has loads of CAT commands that my code needs to answer… this radio is my QRO 20m as rig it sports the 20w amplifier kit from K5BCQ and will put out a whooping 22w! Several contacts from A6 into Europe and some over to Indonesia.. fun stuff, two kits from different vendors together with some own building and coding.. I love it.

On the workbench now is an Arduino CW keyed based on K3NG, the Arduino code is very well written and it has loads of functionality, most of what I will never use.. but as a keyer it is superb.
This is my keyed circuit, super simple stuff, it is here connected to the Mighty Mite as a test, works 100% I am now researching a good circuit for a CW transmitter/transceiver for 40m that will be in the 5 to 10w range to use my new keyer with.


Again, thanks for a fantastic show guys,

73
A65DC, Martin

Colin M1BUU Achieves SOTA “Mountain Goat” Status — With Rig Built ON THE MOUNTAIN TOP

Stiff upper lip OM! MUSN’T GRUMBLE and all that…

Our friend and BITX builder Colin M1BUU has opened up a new area for ham radio masochism: EXTREME MOUNTAIN-TOP RIG BUILDING. That’s right my friends. You read that right. Colin has taken the solder smoke to new heights. Soon, these guys will be pouring scorn on those of us using “shack built” rigs. Congratulations Colin! Well done!

Colin’s write up from http://reflector.sota.org.uk/t/colin-m1buu-mountain-goat/14559 :

The general story goes something like this –
I started with SOTA way back in 2004, aged 24. Just after I found SOTA, I also found love – Fiona and I will celebrate our 10th wedding anniversary in April. You know how the story goes……….
Winter time has generally been quiet in terms of family stuff, so it’s generally this time of year when I activate, usually January to March.
You’ve heard of extreme ironing, right?


Being a prolific builder of radio kits, I thought I would do my own twist on Extreme Ironing – Extreme Solder Ironing!
Today was the day. I took a RockMite kit, a home made key kit and a home made vertical antenna kit up to the summit of Whernside G/NP-004. I assembled the kits using a gas powered soldering iron. Thankfully I took my little tent with me, the weather wasn’t exactly tropical.
The kits went together well and the RockMite fired up first time without any debugging, although the building took much longer than I had reckoned.
I was late on air, but eventually Barry N1EU found me for my first contact. Shortly after followed SP9AMH, OH9XX and finally EU2MM to earn me my needed points. Mountain Goat was in the bag! The QSB was very evident today, QSO’s were tough, except with OH9XX, who was ear blasting. :smile:
Firing up the FT817 (I intended to share my success with as many as possible!), I worked a handful more stations on CW and SSB, but my time was rapidly dwindling.







Finally, I’d like to say thanks for all the support given by numerous SOTA participants over the years, There’s a number of great, inspirational people we’ve lost in that time and I think about lots of them all the time. Roger G4OWG was particularly on my mind today as I learned of the route I took today from one of his posts. I never met Roger in person, but he was a keen chaser and fairly local to me.
73, Colin
Edit – I forgot to put forward my thanks –
Thanks to Dennis G6YBC (Kanga Products) for sponsoring a RockMite ][ ver. 1 PCB
Also thanks to Pete G4ISJ for supplying the solder!

SolderSmoke Podcast #193: BITX 40, OLEDs, KWM-4, Noise Abatement

SolderSmoke 193 28 Jan 2017


Report from Pete on BITX 40 Session with California radio club.

Update on the BITX40 Module Revolution
— Check out the BITXHACKS page. Send in contributions.
— BITX20 mailing list very active.
— Raduino!
— Interview with Farhan with W5KUB — Eliminating the commercial gear.
— BITX 40s on the beach in Australia. FB

Bench Reports:

Pete:
— Color Displays!
— KWM-4
— OLED MADNESS!

Bill:
— Fixing up the old HT-37 HT37 to HT37 QSO with W1ZB
— Dabbling in VHF with Ramsey Aircraft band receiver. NOT FUN.
— Going all IC with Si5351 OLED NE602 rig.
— BANDSWEEP
— OLED Noise and the Active Decoupling solution.

Using LTSPICE as a diagnostic or understanding tool.

Of Waterfalls, Homebrew Rigs and Casual Critics on 40 meters. Words of Wisdom from W8JI.

LEXICON: HAYWIRE TOMBSTONE BIKESHEDDING from Todd K7TFC

Some great recent interviews by Eric 4Z1UG:
Ian G3ROO Origins of ROO Regen at age 8
Hans Summers G0UPL Balloons! NO COMMECIAL GEAR
David White WN5Y ELECTROLUMINESCENT RECEIVER EXPLAINED
Rob Sherwood NC0B

MAILBAG:

Chris KD4PBJ’s BITX 40 with improved stability
Jerry W0PWE built a DIGITIA! Very nice. Worked Keith N6ORS and heard me! TRGHS
Mike AB1YK’s Al Fresco Scratch built BITX. But give that LC VFO another chance Mike!
Steve N8NM 30 meter rig with salvaged CB LC VFO. FB
Keith N6ORS Franken SDR rig with parts from the 1980s. FB
SKN Bandscan from Mike WA6ARA I worked W1PID Jim!
What is Mikele up to?
Rocking Johannesburg and Kirghizstan via local repeaters:


When Bypass Caps are Not Enough: Active Decoupling

I was having a noise problem with my NE602 Si5351 OLED display receiver. There was an annoying high pitched whine in the audio output. The source was easy to identify: If I reached in and unplugged the OLED display, the noise disappeared.

Next I had to find out how the OLED noise was getting into the rest of the receiver. It could have been through the SCL SDA or even the ground lines. It could have been just through capacitive or inductive coupling from the display board itself. A big clue came when I tried powering the display from a completely separate power supply: BINGO! The noise disappeared. So I knew the noise was going into the rest of the receiver through the Vc line that powered the OLED.

I had been powering the OLED from the 5V regulator on the Arduino Uno. In an effort to isolate the noise, I put a separate 5V regulator in the circuit for the OLED. No joy — noise still there. I then tried putting an RC low pass filter between the OLED and the 5V regulator. Still had the noise. Finally I remembered something from the AF AMP circuits of Roy Lewallen, Rick Campbell and Roger Hayward. ( I think Roy was the pioneer on this one.) They all used an “active decoupler” between the first AF amp and the power supply line. I confirmed that it was my first AF amp that was picking up the OLED noise. I built the active decoupler (just three parts!) and the noise disappeared. GONE!

There are only three parts, but the way this circuit works is kind of complicated and not very intuitive. There is a good discussion of how it works here:

www.facstaff.bucknell.edu/dkelley/elec351/Lab/elec351lab5_sp04.doc

 Roy, Rick and Roger were using this circuit to knock down 60 Hz AC hum, but I found that my OLED noise was at around 200 Hz — I figured (correctly) that the active decoupler would take care of this as well. I think this little circuit can be useful in dealing with the kind of noise generated by the digi displays that many of us are now using.

David Rowe has a really interesting analysis of this circuit here:
http://www.rowetel.com/?p=4781

KD4PBJ’s FB BITX 40

Hi Guys!

I have to admit something. It’s a learning experience.
A year or two ago I bought the Bitx boards from Sunil in India and while they are on the To Do list, haven’t been built up yet. I have close to 20 projects on my to do list, so when Farhan’s prebuilt SMT version became available I decided to get one.
I had gone over to TenTec before they shut down and bought a few of their two piece enclosures since I like how attractive they are and also inexpensive.
The Bitx went into the enclosure quickly and I measured a little over 10 W out with my scope. I fed a -125 dBm signal in using my HP8640 generator and could easily hear the tone.
So a really sensitive receiver. Nice and quiet too!
I got a SMT digital dial from QRP Guys and got it in the case. Now I heard a high pitched whine in the background. Nuts!
So I posted to the Bitx yahoo group asking for help in reducing the noise. I built a R/L/C filter network, added ferrites, built a copper clad and brass enclosure for the display. Nada. Noise still there. Adding adhesive copper tape didn’t help either.
This was driving me mad. For some reason, and I don’t know why, one evening I decided to try a gel cell. Success!!! No noise whatsoever.
Here’s what happened….
When I first built the radio in early December I tested it on my operating bench. On that bench is a older Power Designs 0-60V 0-5A linear bench supply.
After adding the display I did integration on my soldering lab bench and for that I grabbed my HP E3610 supply which it turns out is heavy but switching, not linear. The noise was coming from the supply!!
If I hadn’t tried the gel cell it may have taken me a long time to figure this out.
Saturday of last week was my first contact with it. I worked two Canadian stations with it, and both came back to me the first time after I answered their CQ’s. I did have one issue and that’s the well documented drift. During the QSO I watched the display drift upwards as I held the PTT button down. I replaced the 100 pF and 47 pF chip caps in the VFO with disc ceramic parts from Mouser and now it doesn’t drift.
While doing the work in the VFO section I also tweaked the trimmer cap a bit to bring the bottom range up to the start of the phone band, as before the bottom end was below 7 MHz and I figured that didn’t do me much good for a SSB rig to waste a lot of its tuning range on the CW segment.
Here are a few pictures. Mic is home brew too, having made it for my MMR-40 rig.

Hope all is going well for you and looking forward to the next Solder Smoke.

Chris KD4PBJ



Fifteen Back Iissues of “Hambrew Magazine” (from the 1990s) Available Online

They look very interesting. I saw an article by Wayne Burdick. Doug DeMaw was involved. Thanks to Tim at Arrow Antennas for making these back issues available.
You can download the .pdf files here:

http://www.arrowantennas.com/sub/hambrew.html

HB2HB: N6ORS, W0PWE (and me!)

This is so cool. Jerry W0PWE has built a magnificent BITX. With a digital VFO and Termination Insensitive Amplifiers, I think it qualifies as BITX DIGI-TIA #2. Running it “al fresco” he was tuning around on 40 and he heard DIGI-TIA #1 (mine!). As soon as he finished soldering in the power amplifier, he put it on the air and, in his second contact, worked Keith N6ORS — Keith was running his MIN-X rig. Clearly TRGHS. Great work Jerry!
Hello Bill,
Jerry here W0PWE in Iowa. I save up your podcasts and listen to them when I travel. A year or two ago you and Pete got me interested in the BitX and I finally took action. I have plenty of other
projects I should finish but boy was it ever fun to start a new one. This morning I soldered the
last part in my newly hatched Bitx, drug it over to the operating position and had two great QSOs
with it. See attached photo shows the rig as it was during those QSOs.

When I finished my first QSO with W9SX, Keith in WI N6ORS called me. He was running a multi-band Bitx he had built and we had a great HB2HB qso. Awesome!

My rig is scratch built, mostly SMT and generally follows the 40M schematic that Farhan has on
his HFsignals page. I am using the Kopski/Hayward TIAs though and I designed a 6 pole crystal
filter for it since 6 of the 10 crystals I bought were very similar when I characterized them
with my PHSNA setup. It uses the Adafruit SI5351 board and I modified a sketch that LA3PNA wrote for the Arduino.

I designed and fabricated the boards for it using the software and process described by K7QO and
W5DOR. Toner transfer with the Hammerhill Gloss paper is working great. The heatsink on my IRF510 is a little light. I could smell the MOSFET warming up during a few of my lengthy transmissions with Keith.

Now the SWL report. While listening on the receiver portion of my Bitx last week I heard you on
7260 at about 0030Z. I think that was Tuesday or Wednesday. I wished I could give you a call but
at that point my PA was merely a few traces on the computer screen. Hope to hear you again on
40M.

73/72,
Jerry – W0PWE

AB1YK’s FB “Al Fresco” Scratch-Built BITX 20

Mike AB1YK built this very nice BITX20. On a board, al fresco. Very nice. He provides a good write up here:

http://n1fd.org/2017/01/18/first-homebrew-contact-on-my-scratch-built-bitx-20-ssb-transceiver/

 I feel obligated to defend his poor analog VFO. Mike — that oscillator never had a chance OM! You need to nail that coil and that capacitor down! You threw in the towel and went over to the dark side way too fast. Go back and get that VFO stable.

Similarly, I’d say it is time to put away the keyboard and get out the microphone. This is a 20 meter phone rig after all. Allow it to send your dulcet tones across the seas!

But seriously, great job Mike. There are very few scratch-built homebrew SSB rigs on the air these days. Congratulations OM.

N8NM’s SAVED VFO 30 Meter Rig

In early December Steve Murphy N8NM picked up this “mystery box” at a hamfest. Dr. Juliano identified it as an old CB VFO. Even though Steve is deeply committed to the dark side of frequency generation (digital synthesis) I was able to convince him to put this VFO to legitimate and proper amateur radio use AS AN ANALOG VFO. I mean just look at that dial! It would be a sin to connect that beautiful mechanism to a rotary encoder. We see the results below.

Bill:

The 30m rig that I had hoped to have QRV for SKN is finally ready to hit the airwaves! I still have a few odds and ends to tidy up, but it’s essentially done.

Where I ran into problems was my original choice of IF and VFO frequencies: I’d gone with a 13.51 MHz IF because I had the rocks, but that put the 3rd harmonic of the VFO right in the middle of the band. Oops.
Moving the IF to 13.56 fixed that problem, but I still had a spur from that harmonic that needed to be filtered. At first, it looked like a trap on the output of the VFO would squish it, but it ended up requiring a few extra poles of bandpass filtering to get it below -40 dB/c. Now we’re legal.
Anyway, here’s a few pics. The chassis are bent from 22 ga aluminum on my trusty Harbor Freight brake. They’re almost square, they look cockeyed because I still need to make brackets to hold the top and bottom together. The heat sink is overkill for 5 watts, but it was cheap 🙂
Electronically, almost everything between the audio and power amps is straight-up Bitx. The power amp uses a RD16HHF1 driven by my spin on Farhan’s RF-386, and the audio is an LM380 driven by an LM324, with gating between CW and digital mode input handled by a CD4066. The CW tone generator is based on WB0RIO’s “clickless” sidetone circuit, which, while a little complicated, creates perfectly formed CW elements that really sound nice.
I’m still amazed at the stability of the LC VFO; I was monitoring JT65 signals over the weekend and noticed zero drift after warm-up. To keep it ready to rock, it’s powered from the “hot” side of the on/off switch, as is the CW oscillator.
I can’t think of much else to say about it… It is what it is 🙂
73 – Steve N8NM