Slide Show of BITX 17 Build

As I was building this rig, I periodically stopped and took a picture of the board.  I think the resulting slide show is kind of fun.  Check it out:  There is a button to launch the slide show.

http://www.flickr.com/photos/106886073@N04/sets/72157637045750216/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Book Review: "Bunch of Amateurs" by Jack Hitt

The title held a lot of promise, but the subtitle ("A Search for the American Character") hinted at the main problem that I had with the book:  the author (perhaps driven by his editor) seemed to be struggling to prove that there is some uniquely American elements to amateur science and technology.  Early on, Mr. Hitt, makes the preposterous claim that "the rest of the world doesn't have amateurs."  He goes on to write that "In Europe and on other continents, the word hints at class warfare... Amateurs may be taken seriously, but, almost by the power of the word, are kept in their place: isolated outside some pre-existing professional class, some long-standing nobility.  In America, amateurs don't stay in their place or keep to themselves."   

What a load of rubbish!  This claim directly contradicts what many of us have been finding out in the quintessentially amateur world of amateur radio:  as we travel around the world (in person, or via the ionosphere) we find, all around the globe,  guys who have followed shockingly similar paths to ham radio.  From Sudan to Switzerland, from India to Indiana, the story is much the same.  And I'll bet you'll find similar similarities in just about every serious sci-tech hobby (astronomy, photography, etc.).  To claim that there is something fundamentally exceptional about amateurism in the U.S. is, I think, ridiculous.  Mr. Hitt should have spent some time looking at the amazingly diverse and vibrant world of British amateur science and technology.  That alone would have prevented him from straying into these silly claims of American amateur exceptionalism. 

But, all that aside, there is a lot of interesting material in the book.  I liked his description of John Dobson and the amateur telescope builders.  And, somewhat surprisingly, Hitt's description of the DIY Biology movement (these guys are playing with genetics and cooking up new organisms) seemed to capture very well the creative joy and satisfaction that amateurs find when working (just for fun) on their projects.  I was kind of surprised when I found myself identifying with the DIY Biology folks. Their basement labs sounded a lot like our radio shacks.   

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX BUILD UPDATE #17 Arv's Discrete AF AMP

I've been kind of cheating with the audio output from my BITX17:  I've been using one of those little battery-powered computer speakers.   It sounded fine, but hey, this is supposed to be a homebrew project right?  I've already noted my ideological objections to the use of the LM386 CHIP.  The files of the BITX20 yahoo group provided a very promising and completely discrete AF amp circuit by Arv Evans, K7HKL.  I used a 2N3906 and a 2N3904, with a 2N2222 driving them. It works like a charm.    Not a bit of feedback or motor-boating.  It sounds great.  I've already had a contact with it:  Jack, W7YUM is a builder of big amplifiers out in Salt Lake City.  He seemed very impressed with the BITX concept so we may have a Utah BITX in the works. 

 book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Words of Wisdom (on Amplifier Stability)

From "A Simple SSB Transceiver"  by Ashhar Farhan:

"What if your transmitter is unstable?  Don't curse your fate.  All transmitters start out as unstable beasts. Relax."   Farhan goes on to provide some good pointers on how to tame the beast.  

I've had very good luck with the PA in the BITX  -- very little cursing of fate on this project. 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX BUILD UPDATE #16 -- FIRST QSO!!!!!!!!!!!

 

Wow, it is very clear that the radio gods are pleased with my BITX efforts!  I had my first QSO on the new rig today.  And it was with a station in my old home, the place where I got my start in 17 meter homebrew phone:  THE AZORES!  CU7MD.  Very cool.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #15 -- Necessary Mic Amp Mod

I was having trouble with the mic amp on my new Manhattan Discrete BITX 17.  I had it wired as per the schematic, but it just wasn't working right -- I was getting very little DSB out of the balanced nodulator, but everything worked fine if I 1) unbalanced the bal mod or 2) injected audio (from a sig generator) directly into the audio in port of the balancec modulator.  Clearly something was wrong in the mic amp circuit.  I noticed the collector voltage seemed quite low.

Some quick Googling revealed that others had struggled a bit with this problem also.  Nicolae's note was especially illuminating and useful: 
http://users.tpg.com.au/nfieraru/Electronics/BitX20_Mic_Preamp.htm

As Nicolae noted, the 10K value may have worked with lower gain transistors.  We must remember that BITX was (very admirably) designed for minimal cost and maximum use of scrounged parts.

I swapped the 10K resistor for a 39K and all is right with the world.  The band is not yet open here, but I bravely called a European aeronautical mobile station, hoping that he would be my first QSO on this rig.  I think he heard me, but no QSO (yet!).

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #14 -- STABILITY!

Good news on the BITX.  I think I have solved the low frequency oscillation problem in the power amplifier.  I tried running the PA off a separate power supply -- the oscillations disappeared leading me to conclude that the feedback was taking place via the power supply lines.   I put a 22 uF cap to ground from the top of the PA's RF choke.  With this cap in place I can dispense with the separate supply kludge. The amp is stable.

This morning I also resolved a different stability problem.  I'm using a relay for T/R switching.  One set of contacts controls the DC power, the other set was supposed to disconnect the receiver input from the antenna/lowpass filter when on receive.  But I had positioned the relay too far from the LP filter and RX input, so I ended up with this long piece of coax that was hanging off the PA output terminal and carrying lots of RF on transmit.  Yes, this led to oscillations.  I thought about repositioning the relay, but I think part of the problem is that even if optimally positioned, the long unshielded contact levers inside this relay would be radiating a lot of RF and causing stability problems.   So instead I put a small reed relay very close to the PA out and RX in connections.  It carries the signal to the receiver when in R mode, and disconnects the RX when in T mode, without any long coax lines or unshielded relay levers.   It works.

I still have a few things to do:
-- I need to build a proper speaker amplifier so that I can dispense with the amplified computer speakers KLUDGE.
-- I need to get a 3 pole double throw switch and some crystal sockets so that I can switch crystals from the front panel.  Three rocks will cover all of 17 meter phone.
-- I have to build a case for this rig.  I'm thinking wood, with tin or aluminum sheeting glued to the inside (for shielding).  


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

From Bits to Atoms -- Software vs. Hardware

I thought this was pretty good.  On Hack-A-Day.

http://hackaday.com/2013/10/18/guest-rant-from-bits-to-atoms/#more-105097

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Feynman at G-QRP Convention!

What do Richard Feynman and the G-QRP club have in common?

The answer is an annual pilgrimage to Ripponden in Yorkshire, England. The G-QRP club have their convention in a local school and Feynman went there every summer to visit his wife's family. Here's an interview with Feynman filmed at the Old Bridge Inn which is about a mile from where the G-QRP club gather:

http://www.openculture.com/2012/11/richard_feynman_talks_physics_in_take_the_world_from_another_point_of_view.html

Is this enough to make Ripponden the Knack Centre of England?

Regards,  Alan G0RWB

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Yikes! Screeching Transistors Throwing off Blue Light!

I found a quote from Doug DeMaw that I wanted to share.  This one seems appropriate as I struggle with unwanted oscillation (and as Halloween approaches). From the January 1986 QST:

"Self -oscillation occurs not only in the low-frequency and high-frequency spectrum, but it often takes place at audio frequencies!  I have actually heard the transistors "screeching" when strong audio oscillations were taking place in a homebrew transistor power amplifier. On one occasion I could see a bluish glow coming from within the transistors (visible through the ceramic heads of the devices) during a period of instability.  Needless to say, the transistors self-destructed."

I've been having some instability problems with my BITX 17 IRF510 final.  But I think I have the problem identified.  I was getting low frequency oscillations (around 100 KHz).  Tonight  tried putting the IRF510 on a separate power supply.  The oscillations ceased and I am getting a nice clean 3 watts out.   So I'll go back and beef up the decoupling on the power supply lines.


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

20% off on SolderSmoke Book

Just use the coupon code PUMPKINS at checkout:

http://www.lulu.com/spotlight/soldersmoke

(You can also use this coupon to buy Grayson's "Hollow-State Design" :
http://www.lulu.com/shop/grayson-evans/hollow-state-design/paperback/product-20987562.html

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke Podcast #155 BITX17, TEK465

Podcast # 155 is available for download (or you can listen by clicking on the button above):
http://soldersmoke.com/soldersmoke155.mp3

October 14, 2013  (Delayed Back-to-School edition)

Topics covered:

-- BITX Beauty -- Building a BITX17

-- VFO woes, and the wisdom of Doug DeMaw's love for crystals

-- Why does a 55 year old man NEED clear nail polish varnish?

-- How the VFO KILLED the Tek 465

-- Trying to fix the Tek 465 (not for the faint of heart)
 
-- New products:  Justin Beiber Duct Tape, bifocal safety glasses,
magnetic reading glasses, Ward Silver's new book

-- Backwards British Bike Brakes

-- MAILBAG 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

"Robert Ford -- A British Radio Operator in Free Tibet..."

http://www.economist.com/news/obituary/21587201-robert-ford-british-radio-operator-free-tibet-died-september-20th-aged-90-robert-ford

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Nice Slide Show on BITX

https://sites.google.com/site/arvidevans/BITX_QRPacificon..pdf?attredirects=0


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX BUILD UPDATE #13 -- VIDEO TOUR

I hope to get the next podcast out within a week or so.  The BITX has been keeping me busy!


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX BUILD UPDATE #12 -- Relay and PA, BITX 17/10?

As you can see, the board is starting to fill up.  I really like it.  It seems (to me) like the canvas of a painting approaching completion. This morning I put in the T/R relay.  That space in the upper left is reserved for the driver and the IRF510 Power Amplifier.

I got some help from the Chief Designer this week.  As noted in an earlier post, Farhan  advised me to check the mixers.  I knew that I had them wired correctly and that they were in fact mixing, but when Farhan advises you to check something, YOU CHECK IT.  Farhan was right (see earlier post).

It really sounds great.  I know that the filter still has significant ripple in it, but the receiver sounds so good I'm reluctant to mess with it.  Should I de-ripple it?

On the train yesterday I was thinking about this rig, and it occurred to me that my 23.1 MHz VXO/ 5  MHz IF arrangement means that this 17 meter transceiver could also generate signals on the 10 meter band.  Of course, I'd have to build a second bandpass filter, but the radio gods guided my hand and caused me to leave space on the board for just such a filter (see above).  I realize the IRF510 PA wouldn't be too good up at those frequencies,  but when the radio gods speak, you have to listen.   

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Tek Troubleshooting Triumph

Thanks to the manual provided by Jim and the HV test gear provided by Alan Wolke, I was able to finish the troubleshoot on the broken Tek 465.   It is the HV multiplier, U1432.   The cathode voltage is supposed to be -2450.   It initially tested at -1000.    The manual calls for a jumper to be removed to take the HV Multiplier out of the circuit.  As soon as I did that, the cathode voltage went to -2500.   Bingo.

 

Now I have to get a replacement for U1432.    Any carcasses laying around?

 

Thanks guys. 

 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #11 -- Peakin' and Tweakin'

Oh how I love the sound of a newly built receiver!  I'm sitting here listening to G0MJS on 17 meters.  Lots of other stations from across the pond coming in very nicely. 

Earlier in the week I had some sensitivity problems.  I could hear the noise floor, but just barely.  And the receiver just seemed to have trouble inhaling.  So I started poking around.  It seemed that each poke improved things a bit.  I had used Farhan's original schematic (mostly).   Later versions put an additional transistor in the IF amp.  So I went ahead and added that mod.  That helped a bit.  Then I noticed that BFO energy was getting into the AF amp.   So I put a .1uF cap to ground at the input to the AF preamp.  That took care of the RF and did no damage to the AF.  

But the rig still seemed a bit hard of hearing.  This morning Farhan advised me to take a look at the mixers.  I used some junk-box diodes that I didn't know too much about...  I measured the forward resistance and found it to be quite a bit higher than the usual 1N914s.  So I switched all 6 mixer diodes.  That helped noticeably.

I also checked the input bandpass filter.   It seems OK.   In the process I learned to use the EMRFD filter programs (thanks Wes) and the ELSIE filter program (also very nice).

Anyway, the rig sounds great now.   On to the transmitter.  

Farhan advises building the power amplifier on a separate copper clad board.  But I have room for it on my main board.  Should I live dangerously?   


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Occam's Microcontroller

Paul, M0XPD, has what I'm sure is a wonderful article on a simple microcontroller-based rig in the current issue of our beloved SPRAT.   I look forward to seeing it.  And I really like the logo with William of Occam (of razor fame). I have encouraged Paul to take a break from the microcontrollers and build something discrete and analog... like a BITX!  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #10 -- Darling(ton)

Having concluded that I was significantly short on overall receiver gain, I went in yesterday and changed my AF amp from a 40db direct-coupled circuit to a 100db Darlington pair.  I immediately noticed a big increase in audio output. 

I did a quick receiver alignment using my Arduino/AD9860 sig generator.  First I determined the actual bandpass of the crystal filter: 4.998170 MHz -- 5.000960 MHz.   Using a freq counter, I set the BFO at 5.00126.   I immediately started hearing 17 meter SSB signals from the West Coast.  That's always a nice moment:  first signals through a new receiver.  Kind of like "first light" in a new telescope.  Even with the filter ripple, it sounds great.

I think I'm still significantly short of gain.  Audio is still faint. I notice that in the BITX17A they have added a second transistor (Q17) in the second RX receive amp.  Maybe I should try something similar.   Or should I add some gain in the audio chain?

I'm really enjoying this BITX project. 


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Hackers' Paradise

http://hackaday.com/2013/09/23/guest-rant-ham-radio-hackers-paradise/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #9 -- Discretion

With the exception of the PA, all of the stages of my BITX 17 are built.  Over the weekend I put in the DC wiring for the receiver and the inter-stage connections (using the Belden coax with the exposed shield and Teflon di-electric).  It looks nice. 

In my experience, almost all new superhet receivers require a certain amount of debugging and coaxing before they will work.  This one is no exception.  The VFO and the BFO work fine, and all three RF and IF amp stages are also good.  The bandpass filter  that I built passes the desired band and tunes up nicely on the right frequency.  The product detector was acting weird and wasn't balancing out properly, but I got that all sorted.  

I can put an 18.110 MHz signal at the antenna connection and see the signal go through the bandpass filter (with loss), on to the RF amp stage, to the first mixer where it meets the 23 MHz energy from the VFO.  A very messy mixture goes from the mixer to the first IF amp which sends it to the 5 MHz Cohn filter.  The filter works, but it has a lot of ripple, so I need to work on the termination impedances.  Second IF works fine, then the signal goes to the product detector.  AF comes out.  

Here's where the discretion comes in.  Instead of the LM386 chip, I built a 40db two transistor direct coupled AF amplifier. 

So it all works, but the receiver is quite deaf.  I think I just don't have enough gain in the whole system.  I looked at the schematic for the BITX-17 kit.  It very helpfully has total (net) gain figures for the RX.  I can see that my current configuration comes up short.   

Here is what I'm thinking of doing:  I might replace the 40db direct-coupled AF amp with a 100 db Darlington pair.   I really like the discrete Darlington AF amp that KD1JV has in his "all discrete" transceiver:
http://kd1jv.qrpradio.com/ADC/ADC-40.htm  Nice.  3 2N3904's driving a speaker.  I may use that.  
 
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #8

Big progress on the BITX:  All the bidirectional amp stages are done.   A bag of 20 5 MHz crystals arrived from Mouser today.  I put one in the BFO/Carrier oscillator and it fired right up.  I'll soon be checking frequencies on these crystals, looking for four that are closest in frequency for use in the filter. 

While waiting for the mail I built the audio amplifier for the receiver (lower left corner in the picture above).   Here I need some advice/encouragement:  In an effort to keep this rig "all discrete" I decided to dispense with the LM386, and replace it with an AF amp using individual transistors.  I found a circuit in the 1980 ARRL Handbook that I liked.   It has two direct coupled transistors, one NPN, the other PNP.  I went with a 2N3904 and a 2N3906.   The Handbook said it would yield 40 db gain.  I figured this was a close enough replacement for the 46 db gain of the LM386.  

As usual, I'm not sure of the impedance matching.  I built the first AF stage from the BITX schematic (the stage that precedes the LM386).  It goes to a 10K pot.  The wiper of the pot would normally go into pin 3 of the LM386.   I have the wiper going through a 4.7 uF electrolytic into base of the first transistor.  The Handbook says the circuit has an input impedance of 1000 ohms.  Does my arrangement sound OK? 

Output impedance from this Handbook circuit is also 1000 ohms.  I tried it with some HI-Z headphones that I have, putting AF in from my Maplin AF sig generator.   It sounds OK.   Not a LOT of audio available.  But OK.  I may need one more stage to drive a speaker.     

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Inside a Tek 465

The TEK 465 'scope is as they'd say back in the Bronx "a piece of work."  It has real character.  Perhaps a bit too much.  If you look closely, you'll see transistors in sockets.   I had kind of gotten my head around that, when I noticed that many of the transistors were not in sockets.  They looked like they had been soldered to into the holes in the PC boards.  But NOOOOO!  They are snugly in the holes, but they are NOT soldered in!  You can pull them out, then (if you are lucky!) slide them back in.  There is even quite a bit of "ugly construction." with connections floating in the air.  You can really see the influence of tube era thinking in this instrument.

I think I have narrowed the problem down to the HV supply.  Alan Wolke is lending me a high voltage probe.  I hope to be able to get it fixed this weekend.  I need to get it working because my BITX 17 is nearing completion and I'll need the 'scope for the lineup and de-bugging.

The picture above is from:  http://www.eevblog.com/forum/projects/tektronix-465-repair-and-restoration/   More pictures of the scope are available there.  Also see http://www.spurtikus.de/basteln/repair/tek465/index.html for more scenic views of this instrument.


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Battushig has The Knack (Mongolia and the MOOCs)

"How does a student from a country in which a third of the population is nomadic, living in round white felt tents called gers on the vast steppe, ace an M.I.T. course even though nothing like this is typically taught in Mongolian schools?"

"Most homes in Ulan Bator have Internet connections, and almost everyone, including nomads, has at least one cellphone. Even on the steppe, with only sheep in sight, you can get a signal."

http://www.nytimes.com/2013/09/15/magazine/the-boy-genius-of-ulan-bator.html?pagewanted=all&_r=0

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update # 7

As you can see (above) I've made lots of progress on the BITX-17.  Going counter-clockwise from the lower right, you can see the mic amp, the BFO/carrier oscillator, the first mixer, the first and second bi-directional amplifiers, the diode ring VXO mixer and the VXO.

I plan on building the whole rig (including the power amplifier stages) on this wonderful piece of PC board (thanks to Jim, W8NSA).

I had what I thought was the brilliant idea of using LEDs for  all the T/R switching diodes.  I thought I'd use red for receive and blue for transmit.  I consulted with the BITX yahoo group and cooler heads prevailed.

The design has an LM-386 as the speaker amp.  I'm kind of bothered by this -- I'd prefer an all-discrete component rig, so I am thinking of building an AF amp with discrete transistors instead, perhaps the circuit from Roger Hayward's RX for the Ugly Weekender.  What do you all think about this? 

I'm having a lot of fun building this rig.  If anyone out there is looking for a fall/winter project, build one of these.

I have to order some 5 MHz crystals for the filter and oscillator.  Mouser has them at about 70 cents each.   


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #6: Rock Steady

So, having given up on the VFO,  this week I built a VXO.  The IF in my W4OP-built Barbones Superhet is at 5 MHz.   That receiver has a VXO running at 23.133-23.168 MHz with two crystals switchable from the front panel.  My plan is to build a 5 MHz filter for the BITX 17.  So I just plucked one of the crystals in the Barebones RX and used it to test and tweak the VXO.  Trying different values for the series inductor, I got wide variations in freq swing.  With .7uH I could only pull the rock 9 kHz (too little).  With 5.6 uH, it was pulling 434 KHz (way too much -- it was acting like a VFO). 3.213 uH was just right:  With my 19-148 pF variable cap (with 53pF in series) I got a swing of 22 kHz, with crystal-oscillator stability.

I know, I know:  I could have done this with a DDS chip, or with an SI570.  But simplicity is a virtue, and the BITX is all about simplicity, right?  Having recently built a DDS RF generator, and now this simple three transistor device, I must say that I like the simple analog circuit better.   But hey, that's just me.  I'll talk about this in the next podcast.

Today I built the mic amp circuit.  You can see it off to the right of the VXO.

One of these days I'm going to have to actually troubleshoot and fix my Tek 465.  But I'm
afraid of that thing!  The voltages in there are HIGH, and so is the circuit complexity.  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Moon Launch from Virginia (video)

NASA launched a mission to the moon last night.  The rocket went out of Wallops Island, Virginia and was visible from Washington D.C.   I forgot about it, so we missed seeing it ourselves, but this fellow got a nice view from the balcony of his Washington apartment. 


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Burning Man: Probably more Fun than a Hamfest!

Check out this report from the Burning Man event.  Two intrepid nerds head out to the dessert  (with ham radio gear) and appear to have an amazing time. 

http://blog.thelifeofkenneth.com/2013/09/my-first-burn.html


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

NASA needs Ham Help! Say HI to Juno (on its way to Jupiter) on 10 meter CW!

This is really interesting:

http://www.jpl.nasa.gov/hijuno/

Thanks to Richard, KK4JDO, for the heads-up.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build UPDATE # 5: ADRIFT!

Sometimes it is better to have LESS test gear.  Watching my 5 MHz VFO on the frequency counter was driving me nuts.  If I hadn't had the counter, I might have been satisfied with the VFO.  Ignorance is bliss!   It did settle down a bit.  But then it would wander off.  I hated watching it drift around.  I have been spoiled by Doug DeMaw's VXOs.   So, I went for the VXO.   It will run around 23 MHz.  I'll build the filter at 5 MHz.  That's definitely the plan.  For now. 

I intend to go back and build a real VFO someday.    There seems to be a lot of magic and lore involved.  Bees Wax!  Hot Glue!  Nail Polish!  Q-Dope!  Air-wound coils!   

TEK 465 is still broke.   I think it is the high voltage supply or (less likely) the CRT. 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Fixing TEK 465 Oscilloscopes

I'm having TeKnical difficulties.  My beloved Tek 465 'scope quit on me.  I'd been running it continuously for a day or so, watching the output on my BITX VFO.  Then, suddenly, it blew the 1.5 amp fuse.  I replaced the  fuse, but afterwards the trace was gone and the "Low Line" light was acting weird -- on when it should have been off, then flickering.   I consulted with Alan Wolke.  He happened to be out at TEX HQ in Beaverton, Ore.  He provided some good suggestions, but before I had a chance to try them, the trace came back.  I attributed this good luck to the Radio Gods being pleased with Alan's presence in Beaverton... but my reprieve was short-lived.  Trace went out again today. 

I found this video of the legendary Jim Williams (RIP) fixing a Tek 465.  (Check out Jim's junk box!)
I'll start by checking the Tantalums.  I may get lucky. 

If anyone has any other suggestions, send them this way.  The Tek scope may be old, but it is a COMPLICATED piece of gear... 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Updat #4 VFO Stability

I wasn't quite satisfied with the long-term stability of my VFO.  It seemed like it was drifting about 70 Hz per hour, even after the initial warm-up period.   So, all out of Q-Dope, I went to the local pharmacy in search of clear nail-polish.  (My family was making fun of me.)   I got home and applied several coats of "Sally Hansen No Chip Top Coat Vernis de Protection."   I let it dry a bit, then started watching the frequency counter.  At first results were disappointing.   Drift continued.  Now it seemed to be drifting up!   I cracked the books.  EMRFD has a good chapter on temperature compensation of VFOs, but the process seemed painful.    I wasn't looking forward to it.

I left the VFO on when I went to work, noting the freq as I departed.   Ten hours later I returned, and was delighted to find the frequency almost exactly where I left it!  It may have taken a while for the nail polish to completely dry.    I'll leave it running again today to see how it does.


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #3

This weekend I built the VFO.   I used Doug DeMaw's FET Hartley, from his "QRP Notebook," page 50.

Getting a VFO into the desired frequency range always seems to involve a bit of "cut and try."  Not only do you have to get in the correct freq range, but you also have to try to get the tuning range of your variable cap (or coil) to match the band you want to cover.  In my case, thinking of 20 meter SSB, I need about 200 kHz of tuning range.  And sticking with my 9 MHz (for 20) and 13 MHz (for 17) plug-in filter plan, I need the VFO to be in the 5 MHz range. 

That main tuning cap you see above has more capacitance than necessary (19-148 pf).  One option would be to pluck out some of the rotor plates (been there, done that).  But that seems a bit barbaric, so instead I just reduced the overall capacitance by putting a smaller fixed capacitor (about 20 pf)  in series.      

Yesterday I had it percolating nicely.  Waveform looks beautiful on the Tek 465.   But it was drifting too much.  I had a cheap plastic trimmer cap in there.  This morning I replaced it with a more substantial ceramic trimmer.  This seems to have improved stability quite a bit.

I need to put some stabilizing substance on that toroid.   DeMaw prescribes Q-dope.  I'm all out.  What is the field expedient substitute?   Was it clear nail polish? 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build: Update #2

Not much progress to report.  But I have been thinking about the filter frequency.  Here is my latest idea: 

Maybe I'll build the VFO in the 5 MHz range.  This would allow me to use the 9 MHz Yaesu filter (and associated crystals) that Steve Smith sent to me (see above).  With this I could be on 75 and 20 meters. 

I could build another filter at 13 MHz and, using the same VFO in the 5 Mhz range, get on our beloved 17 meter band.  I kind of like the idea of plug-in filters. 

You can see my ideas for the board layout.  I'm thinking of a Doug DeMaw Universal Hartley VFO inside the box shown above.   The tuning cap you see is out of an old Heath QF-1 Q Multiplier.  It has a very nice reduction drive built into the tuning shaft.  It measures 19 to 148 pf.     
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Building the BITX! Update #1

There it is guys:  A blank canvas of copper-clad board.  A clean slate ready to be filled with the components for a BITX transceiver.  As you can see, I am fighting my "build first, design/plan later" tendencies.  No real design work for me on this one (thanks Farhan!) but I am trying to plan where everything will go on the board.  (Thanks to Jim, W8NSA for the board.)   I'm going to build it Manhattan style (perhaps with an ugly dead bug or two).  I'm starting with a big board because I always seemed to end up with a shortage of space.  It looks like I can easily get all of the circuit (minus the PA) on this board.  I'll build the PA on a separate piece of copper-clad.

I'd like to build it for 17 meters, but if I stick with the 10 MHz filter that means I have to build a VFO at around 8.1 MHz.  That's not impossible, but in my experience it is easier to build simple, stable VFOs at lower frequencies. 

 

I notice that there are a lot of cheap crystals available at higher frequencies.  So, instead of keeping the filter at 10 MHz and trying to get the VFO stable at 8.1, what do you guys think about keeping the VFO in the 4 MHz range and  building the filter with crystals in the 14 MHz range? 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Pete Juliano's KWM-4

 

Pete Juliano, N6QW, has authorized me to provide SS Daily News readers with a look at his magnificent KWM-4, a solid state version of the legendary Collins transceiver.  This project is in the Summer edition of QRP Quarterly.  Amazing job Pete! 

 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

A COOL Norwegian "S" Meter (video)

Immaterials: Light painting WiFi from Timo on Vimeo.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Peter Parker's Video on SP5AHT's Phasing Receiver

There are so many very cool aspects of this project:  I love the phasing receiver arrangement -- it uses the same basic concept that allows my old HT-37 to generate SSB (I struggled to understand it as a kid, and finally succeeded!).   The use of the mobile phone as an audio spectrum analyzer is wonderful.  The N3ZI signal generator looks a lot like the DDS project I was working on (I should have bought N3ZI's! ).  I've been seeing these square pattern PC boards in many projects lately -- I may try this in my next project.  And of course, it is very cool to see a circuit designed in Poland being put to use by a fellow radio amateur in Australia -- a good example of the International Brotherhood of Electronic Wizards!

Here is the page for the SP5AHT rig that inspired Peter:

http://www.sp-qrp.pl/modules.php?name=Content&pa=showpage&pid=54

It is in Polish, but Google should translate it, and, in any case, we all speak Schematic!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

"Chart of Electromagnetic Radiations"

Wow, all you need to know, right here on one poster!  They even cover particle/wave duality.  I tried printing it up in hi-res but the uncertainty principle seems to be interfering! Get yours here:  http://www.flickr.com/photos/llnl/9403051123/sizes/l/ 


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Oscillo-porn! A $500,000 Oscilloscope! (video)

I don't know,  I think I like my Tek 465 better!  But if any of you guys are thinking of buying one of these, PLEASE do so via the Amazon link on my web page!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Dipoles in Space! Millions of them!

http://www.wired.com/wiredscience/2013/08/project-west-ford/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke Podcast #154

SolderSmoke Podcast 154 is available for download!

http://soldersmoke.com/soldersmoke154.mp3

August 11, 2013

-- Alligators!  Real Alligators! (see picture below -- look closely)

-- Ten meter beacon project (with Arduino and Reverse Beacon Network)

-- Telescope repair:  Chap Stick as lubricant, and the perils of macular pucker!
 
-- HW-101 saved from cannibalism!
 
-- The Wonders of WSPR and our need for instant feedback and gratification.

-- QST Review of SolderSmoke, The Book.
 
-- MAILBAG

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Kishan Has the Knack! (video)

Many of us were staring out similar windows, also dreaming of model airplanes, and of transmitter circuits, and telescopes, and rockets... This video runs only 12 minutes.  Don't be deterred if you don't speak Hindi -- the story is easy to follow.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Who Invented the Transistor?

http://www.beatriceco.com/bti/porticus/bell/belllabs_transistor1.html

I dunno.... Roswell?  Really?  But I find myself attracted to anything that involves the use of iron pyrite and cats' whiskers in radio.  Mike, KL7R, sent me a bunch of fools gold from Alaska and it turned out to be better than galena as a detector. 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Homebrew Transistors (video)

So you are using store-bought transistors eh?  APPLIANCE OPERATOR!

Check out Jeri Ellsworth's very impressive production of NMOS transistors.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Solar Field Flip! (video)

Too bad we are not in late March.  This event has such great April Fool's potential:
Some ideas:
-- You'll have to rewind all your toroids!
-- You should switch the braid and the center conductor on all your coax!

I like the "cup half full" sentiments in this video:  The second half of Solar Max is about to begin!

Thanks to Kim VK5FJ for sending me this.






Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SALE: SolderSmoke book for about $16 (save 20%)

This coupon will get you the SolderSmoke book for around $16. Valid through August 9.

http://www.lulu.com/spotlight/soldersmoke


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Big Data and the Square Kilometer Array

All of this is very interesting, but SolderSmoke readers will probably find the last ten minutes most interesting.  

http://www.youtube.com/watch?v=dzlwhP5JejA

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Soul in an Old Telescope

I like this telescope.  The owner built it in 7th grade and is still using it at age 70.  I'm still using the Drake 2-B that I bought with newspaper route money, so understand the sentiments.  

http://makezine.com/2013/07/29/through-a-diy-telescope-brightly/ 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20