Colin's BITX is Receiving!

Wow, quite a bit of progress at M1BUU since our last look (see below).  I must admit, that Arduino DDS board looks quite nice sitting there in the VFO territory.  In his original BITX20 article Farhan recommends a pause before the construction of the final portions of the transmitter -- the builder is advised to sit back and enjoy the receiver that has just been created.  Colin is at that point!   Congratulations Colin.  He has noted that his board is a bit(x) smaller than mine.  Maybe he should stick with Farhan's recommendation and build the PA and driver on a separate board.  This will also help prevent the dreaded oscillations -- no need to tempt fate or anger the radio gods! 

Hi Pete,

Another great SolderSmoke episode this weekend, I really like the humour between you and Bill! I listened to SS whilst melting solder on my BITX project.

I had really wanted to get my BITX working as a receiver before the end of the weekend, but Lewis Hamilton and his (successful) bid to become Formula 1 World Champion, put an end to that idea! I also decided that I wanted to buy some better quality capacitors for the band pass filter, so I've ordered them today.

I fired up the receiver chain for the first time this evening from where the BPF should be, right through to the AF amp, I'm pleased to report that I seem to have created a working superhet receiver! I heard some BC breakthrough at certain points of the tuning range and the rig receives the second harmonic of my Rishworth Buildathon 40m transmitter beautifully (on right part of dial too!). I hadn't tested the RX IF amps or AF amp before, but they seem to be doing just fine.

I'm so pleased to have got so far, and I'm very pleased with the build. That big copper clad board doesn't look so big now, but I think I have room for the TX/RX switch, BPF, RF driver, RF PA and LPF which I still need to add.

Thanks for the encouragement and advice so far, I doubt I'd be feeling so elated at this point without it!

This is going to be a really cool rig!

73, Colin M1BUU

Hi Colin,

 

Two words come to mind: Absolutely Superb! Wow that is such a work of art. I may never show another one of my projects as you have set the standard and benchmark.

 

You also have demonstrated building from the back end which we discussed in SS168. Now what you have built is a part of the test system.

 

Really outstanding. Be sure and video your 1st qso and share on You Tube.

 

Bravo!

 

73’s

Pete

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Pete Builds a Michigan Mighty Mite

We have been distributing quite a few 3.579 MHz crystals, but until today we hadn't seen a single new Michigan Mighty Mite.   I commented on this in the last podcast.  Pete came to the rescue and built one: 

Hi Bill,

     The MMM was built – took me a long time (about 30 Minutes so it was kind of slapped together). The most time was consumed drawing squares on the sheet metal. I used a pill bottle cut down for the coil.

     Used a piece of Home Depot sheet metal for the based. I highly recommend a .01 Ufd from the 27 Ohm to ground –key clicks are awful.

     BTW the circuit can be modified so that the tuning cap is soldered to one side of the coil and the other side to ground –essentially the tank tuning cap is in series with the 0.05 bypass cap and is effectively across the coil. Tribal Knowledge

    The CLA lives on!

 Pete

VIVA EL EJERCITO DE LA LIBERACION DEL COLORBURST! VIVA EL CLA! 

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Pete's Michigan Mighty Mite Manhattan MePad Noodle

New recruits have been signing up for the Color Burst Liberation Army.   We have been sending out many more 3.579 MHz crystals. Pete Juliano was doing some noodling and came up with this plan for Manhattan pads or Me(Maine)Pads.   All you need is some copper clad board, a pair of Home Depot tin shears and some super glue. Cut out the pads, glue them down, add components and get the Mighty Mite percolating.  

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FINALLY! A Computer Made with Discrete Transistors!

• 

Note the discrete BJT transistor T-shirt.  Note the haunted, obsessed look in his eyes.  This fellow is building a computer out of discrete transistors.   He clearly has The Knack.  
http://hackaday.com/2014/11/22/a-4-bit-computer-from-discrete-transistors/


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SolderSmoke Podcast #168 Software Inefficiencies! DSB Blues! Schematic Errors! QRO Confessions!

SolderSmoke Podcast #168 is available. 
22 November 2014 

http://soldersmoke.com/soldersmoke168.mp3
The benefits of software inefficiency.
Don't throw a wet blanket on computer baby steps.
DDS-ing Pete's old boatanchors and Bill's BITX. 
Bill's DSB amplifier woes: a JBOT unfairly scorned.
Getting ready for solar-powered beach DSB.  
Michigan Mighty Mite Crystal Offer -- FREE ROCKS!
Tribal knowledge: Beware of mistakes in published schematics!
QRO update: Working Japan on 17 meters. 
Happy Thanksgiving! 

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Tube Transmitter in a Cuban Cigar Box

Beautiful use of a cigar box by Ben, KK6FUT.   Ben is working in close proximity to Pete N6QW and has obviously fallen under the influence of Pete's "Build Something With Tubes"  field. 
Watch out for the high voltage Ben.  You aren't in Arduino-land anymore!  One hand behind the back OM! 

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Impedance Matching Transformers -- Pete's Magic Decoder Ring!

We got some questions on this and Pete was kind enough to write up some notes on the topic.  We may talk more about this during the next podcast (Saturday): 

Broad Band Impedance Matching Transformers.

Broad Band impedance matching transformers are designed to transfer power over a wide frequency range. More basic you have an amplifier that has an output impedance of 200 Ohms and you want to match that to a 50 Ohm load.

So what is the magic decoder ring so that you get a 4:1 match, ie going from 200 Ohms to 50 Ohms. Getting technical for a moment the maximum power transfer theorem says maximum power is developed when the source is matched to the load.  The Broad Band Matching transformer enables that to happen over a wide frequency range.

So how do we get from 200 Ohms (the source)  to 50 Ohms (the load)? Just as there are many airlines that fly from LA to NY so it is with the matching approach. We will cover several.

First a short discussion about broadband cores themselves. One of the most common cores for HF work is the type 43 core which is good up to about 50 MHz. For transformers up to 200 MHz then the type 61 are a better choice. Typically at HF the FT -37-43 is one of the more common ones see (3/8 inch in diameter), as is the FT-50-43 which is ½ inch in diameter. The iron powder cores are not the 1^st choice for broad band matching.  

#1 Way:

Build a transformer that has a  primary of x number of turns (and since it is large, 200 Ohms will have more turns) and the secondary will have y number of turns ( and since it is smaller, 50 Ohms, will have fewer turns.) The transformer action is based on the ratio of the Primary turns Squared to the Secondary Turns squared. Our transformation is 4:1.

Thus if we divide the primary turns squared and divide it by the secondary turns squared the result is 4. Here are some example: if we had a primary of 8 turns ( 64) and a secondary of 4 turns (16) – 64/16 = 4. So that is our transformer a primary of 8 turns and a secondary of 4 turns. When building these transformers use two different colors of wire as that makes it much easier to identify the windings. Observe the phasing, meaning the end you connect to the collector of your output transistor is the start end. That same start end for the secondary winding is the output “hot” side of the secondary.

#2 Way.

The same ratio holds in going from 200 to 50 Ohms. But this time we will use a single winding of 8 turns and at 4 turns we will have a tap for the 50 Ohm point. Since that tap will very likely have Dc on it connect a 100 NF cap at the 4th turn winding and this is the output. What you have just done is create an auto transformer.

#3 Way.

At time one may have an oddball transformation and you can cascade transformers and multiply their individual turns ratios. At one time I needed a 9:1 transformation. I built a 2.5 transformer and then hooked that to a 4:1 and the result was a 9:1 transformer.

The attached table has “worked out” some common matches that are often needed like matching a 50 Ohm amplifier to a 500 Ohm Crystal Filter which is a 10: 1 match. This is easily done with a 6 turn primary (50 ohms 6^2 = 36) and the secondary has 19 turns ( 500 Oms 19^2 = 361). 361/36 = 10.03:1. Close enough for ham radio! The 1^st way is probably more preferable for this application.

Pete N6QW

11/2014

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Electro-mechanical Heaven.... with Hell (Hellschreiber)

Bob LeDoux sent us a link to a really amazing site about the Hellschreiber system.  The site is filled with great videos, pictures, and animations like the one above.  Lots of radio history too.  Check it out: 

http://www.nonstopsystems.com/radio/hellschreiber-function-operation.htm 
This is all the work of F. Dorenberg, N4SPP.  Thanks OM! 

Bob writes:   I'm working on a microcontroller based reader for
this mode.  For old fossils, like us, this mode looks perfect.  It can
be sent using simple CW equipment and it appears to be a great
replacement for those who are tiring of Morse code.
Its perfect for Knack victims. We can even build mechanical printers. Thanks Bob!


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Pete's Video on Connecting Arduinos and DDS chips (video)

After watching all Pete's work with the smaller Arduinos, that Uno R3 board seems HUGE.  That's what I should stick with.   Great idea using those robust terminal strips.  Thanks Pete. 

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Pete and Ben's "Let's Build Something" Direct Conversion Receiver

This direct conversion receiver is part of the "Let's Build Something"  project of Pete N6QW and Ben KK6FUT.  Publication will be in QRP Quarterly late in January 2015. Pete reports that the front panel is a piece of galvanized sheet metal from Home Depot –total cost 82 cents.

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N2CQR WINS ARRL SWEEPSTAKES! AGAIN! (video)

We did it AGAIN!   Winners in the Homebrew Double-Sideband QRP Northern Virginia Category!  Sweet!  I can't wait to pick up the trophy!   

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The Amazing Rigs of Lee Snook, W1DN

Back in March 2013 we ran a blog post linking to a video of a beautiful superhet receiver built by Lee Snook, W1DN (that's his shop).   Then the video disappeared.  Today Peter Parker, VK3YE, alerted us to the reappearance of the video.  Some Googling led me to Lee's YouTube channel and many other videos of some truly amazing homebrew projects.  

Here is his YouTube Channel:  https://www.youtube.com/user/swradios/featured

And here are all his videos: https://www.youtube.com/user/swradios/videos

Check this out digi fans (from his QRZ page):





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At the Comet

That's an awe-inspiring "selfie"!   This looks like something out of Kubrick's "2001 -- A Space Odyssey." Congratulations to the European Space Agency! 

Using the CIVA camera on Rosetta’s Philae lander, the spacecraft have snapped a ‘selfie’ at comet 67P/Churyumov–Gerasimenko. The image was taken on 7 September from a distance of about 50 km from the comet, and captures the side of the Rosetta spacecraft and one of Rosetta’s 14 m-long solar wings, with 67P/C-G in the background. Two images with different exposure times were combined to bring out the faint details in this very high contrast situation.


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Colin's BITX

With advice and tribal knowledge from N6QW and MeSquares from W1REX, Colin M1BUU, is making excellent progress on his BITX.  I see that he has some territory on the board reserved for a DDS VFO.  That's fine, but here's and idea for Colin and other builders:  Why not build it with the standard VFO first and then add the DDS or Si570 VFO later, perhaps as an external accessory?   That way you get the experience of building an LC VFO -- the full BITX experience. 

Yea, it is hard to imagine Paul M0XPD as a newcomer to the hobby such a short time ago -- he is definitely now in the ranks of the esteemed digital Elmers.   

And yes Colin, we do hope you avoid unwanted oscillations.  Because of Farhan's great design you have a good shot at avoiding this plague.  But be prepared OM.  It happens to the best of us.  A lot.   Stiff upper lip!  Never give in!  

*************

Hi Bill,
I enjoyed your video about your Arduino experiment. You bet me to it! I'm really looking forward to getting my version of an Arduino powered BITX up and running.

Steady progress is being made, yesterday I added my first bidirectional amplifier to the build. I now have the mic amp, BFO, balanced modulator and first amp completed. I tested the BFO on it's own and got a respectable looking signal out of it and with a good swing below 10MHz.

Next I need to add the crystal filter, second IF amp and mixer. Pete's video will help for the mixer! BTW, I'm using the ver3 schematic but I intend to use the ver1 band pass filter.

I set out building the circuit following the N2CQR layout diagram but I've already run short on space! I do have a good excuse though, my board is smaller than yours (10"x6").

Despite my best intentions, I'm falling back towards old habits of making my circuits physically small. I'm using MeSquares in order to try and force myself to space things out a bit. I do hope that I don't end up with any unwanted coupling!

I must try hard to leave lots of space between the next bits of circuit.

I was listening to SolderSmoke 104 today and Paul M0XPD was introduced as a new ham. Little did we know that Paul would become such a big player!

73, Colin M1BUU

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Tricycle Mobile Contact

I couldn't resist posting this picture of the vehicle used by Budd, W3FF.   I talked to him yesterday on 17 meters -- transcontinental -- as he pedaled home in California on his magnificent trike.  He wasn't using the quad in the picture (he was on a vertical). The  six meter quad is fantastic.  He worked Japan with this rig on six. He has a trike trailer that carries his linear amplifier. 

More on Budd and his trike mobile operations here: 
https://sites.google.com/site/w3ffhomepage/

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DDS amplifier

Tony, G4WIF, asked about an amplifier to boost the output of the AD9850 chip.  Here is Dr. Juliano's prescription: 

You might find that once you plug that DDS into a circuit you may not quite get 1 V pk to pk  and in fact after about 10 MHz it really starts to sag. See the attached drawing as you can put this “afterburner’ on the output of the DDS. The isolated output is good if you are interfacing with “toob” type equipment –it can be left off if you are doing SS or just left in place. This is the output from the amp and as you can see fairly clean.

 

73’s

Pete N6QW

 

 

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Digitizing my BITX17 with an Arduino and an AD9850 chip

This is only temporary!  My analog, discrete, hardware-defined BITX17 was NOT harmed or even modified for this little experiment. 

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Background on the use of Si5351 -- code and integration with Arduino Nano (video)

I somehow missed this one.  Here Pete talks about how the use of the Si5351 in ham radio has been evolving, who has been working on it, etc.  

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Pete Goes Superhet with the Si5351 generating BOTH VFO and BFO (video)

Congrats to Pete for his amazingly fast development of a 40 meter superhet receiver using a single Adafruit Si5351 paired with an Arduino Nano for ALL of the frequency generation.   No more VFOs, no more crystals.  It sounds great!   Amazing stuff.  

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BIG Amplifiers with SMALL Microcontrollers and LOTS of Tribal Knowledge

Hi Bill,

I wanted to forward to you a slightly edited email I sent to one of our podcast listener’s as I think this is a really good example of some “Tribal Knowledge”.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Hi OM,

Ham radio publications are much like the Internet –all that is published must be scrutinized. One such publication had a beautiful QRP to QRO amp using a 3CX800A7. A few watts in and 800 Watts out. My daughter was in FM radio broadcasting and I told her to introduce herself to the station engineer and to look out for any pulls – then the floodgates opened –about a week later I had a 3CX800A7.

So I started to work on the amp. The circuits just didn’t make sense and parts were missing that would make it work correctly. I contacted the author and here is what he shared. He built the amp but never did get to proof the final article. In fact he sent me his notes and sketches which were correct. Thus I could have never built that amp using just the article. I built it for one band, 20 Meters. It has a tuned input and a Pi-L output so is quite excellent on harmonic reduction.

Oh BTW this amp caused me to learn about PIC Microcontrollers. You cannot hit the 3CX800A7 with HV voltage until the cathode is warmed up (must be a female tube). That time delay is 3 minutes. I could not find a suitable time delay relay with a 3 minute delay that didn’t cost an arm and a leg. So that is when I thought about using the PIC16F84 as a time delay relay. Later I ported that over to a 12F675. The cost was less than $10. In the 3CX1500A7 amp ( another free tube)  I have two microcontrollers in there. One is used for a three second step start on the filaments (don’t want to shock the filaments with inrush current) and the second for the 3 minute delay before starting the HV step start sequence.

You can see the “Big AMP” on my website at http://www.jessystems.com.

There was only one problem – I was worried about the cooling of the tube so I made sure there was plenty of air which I dump into a very small sub-chassis and the exhaust is out through the tube. Well “Dah” large volume in and small port for exhaust and you have a jet engine sitting on the desk top. Man it was loud – I would wear headphones when it was working.  When I built the 3CX1500A7 amp I used a larger plenum so not as loud.

There are several key points I want to make about tribal knowledge:

1. Turn off the soldering iron and spend a good deal of time “noodling” over the circuit so that it is clear what each function will do and that all the wires connect to something.
2. Contact the author and ask lots of questions and you might be surprised to find out the published design is not what was designed!
3. Look for uncommon solutions to build problems. Many times parts used in the articles are so unique that only one exists in the whole world and it is installed in the authors unit.
4. The amp was built in 2000 and the use of the PIC16F84 as a time delay for an amp was a bit leading edge but don’t be afraid to employ some advanced technology into your projects. [Today an Arduino built into the amp could do time delay, temperature control of blowers, SWR sensing, grid trip protection and even warm your coffee.]
5. In the Big AMP I figured out how to keep the blower going for about 1 minute after the amp is turned off to “cool down” the tube. The point here is to think about not just the amp itself but refinements to make that $600 tube last for a very long time thus filament current inrush protection and tube cool down.
6. Don’t forget SAFETY – there is 2000 Volts @ 1 amp running around chassis–it is an electric chair sitting on your desk top. I included a microswitch that when the top cover is off it de-energizes the HV circuits. See if you can spot it in the photos.

73’s

Pete N6QW

PS The amp really does exist –see below.

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