Saturday, May 16, 2020
Video on Galaxy V VFO IN USE with BITX40 Module -- 40 meter Bandsweep
Check out that fancy frequency readout. No glowing numerals here. But it does the job.
Friday, May 15, 2020
Nick M0NTV's Quarantine Rig: The Bread Bin 80
Hi Bill,
Hope you are keeping well and staying safe.
Just thought I’d let you know about a homebrew project I’ve just completed. I call it the Bread Bin 80 - you’ll see why!
It is a single band (80m) SSB transceiver that puts out 25-30W of clean RF. It uses the familiar pairing of Arduino Uno + Si5351 (with 16x2 LCD screen and rotary encoder for tuning). Other than this though it is largely an analogue beast - which I thought you might like!
I made my own double balanced mixers which work really well. But the Si5351 can’t generate the 7 dBm of local oscillator signal to drive them so I then had to build a simple one transistor RF amp for each clock of the Si5351. I even went above and beyond the call of duty and home-brewed my own IF crystal ladder filter (although this was actually a kit).
The rig has a three stage IF cascade amplifier with 2 back to back JFETs in each stage + AGC and analogue S meter. There is something very satisfying about seeing the needle bob about as you are listening. I also put in a switchable analogue audio filter in front of the audio pre-amp which cuts out some of the higher frequency noise on the band.
Overall I’m really pleased with the rig. I’ve been working stations all over the UK and into continental Europe and getting some great reports. Except the one guy (who shall remain nameless) who wasn’t the least impressed that I was working him on a homebrew rig: he was only keen to point out that my antenna must be far too low to give me such an attenuated signal!!! I guess you can’t please everyone.
Anyway, I’ve done a bit of a write up and included some photos (outside and in) on my QRZ page if you are interested:
Thanks for sharing your home brewing story about your short wave receiver on YouTube. I’ve enjoyed following that and seeing it progress. Those little ‘Altoid’ tins are great aren’t they.
Thanks again for all your encouragement through the Soldersmoke podcast. I really enjoy it.
Stay In The Shack!
Thursday, May 14, 2020
N5GTF's FULLY INDOOR Quarantine Receiver and Antenna
Mike N5GTF deserves special recognition for his truly remarkable SITS (Stay In The Shack) quarantine project. It is not hard to build receivers and transmitters that stay in the shack; Mike went the extra mile by keeping even his antenna inside during lockdown. Well done Mike! But that cardboard frame for the antenna seems to be crying out for some sort of inspirational slogan. Can we get a big "SITS!" in there? 73 Bill
Hi Bill,
Thought I would share a few photos of what happens when one randomly selects things from the junk box after being inspired by Pete's recent posts about phasing SSB. It starts with a 10.7MHz crystal filter because it was large and shiny. This will prove to be somewhat inauspicious, but I'd had a pair of them for longer than I can remember... Then there were several ferrite toroids and a handful of swap meet diodes. Instant mixers, (just add enameled wire). A few 2N3904s and an MC1350P, plus a few more toroids (and wire). I'd picked up some TDA1015s awhile back. They have both a power amp and a preamp, so one of those as well. Also, an Arduino and Si5351, because Charlie Morris, ZL2CTM, has been so generous in sharing his knowledge on how to use them. Finally, about 12 feet of 14/2 w/G and a 365pF variable cap for an indoor mag loop.
Not the best reception though not bad considering the antenna's in the basement with house wiring and metal duct work in the ceiling. The biggest issue is the IF and my choice of LO frequency. I've got the LO below the IF and the LO second harmonic falls inside the 40 meter band. Definitely need to fix that and move on to the transmit side.
Visits to both SolderSmoke and Pete's blog are on my daily agenda. Thanks to you both for the frequent updates of interesting content and for providing a way to get out without going out.
Mike, N5GTF
www.mikesflightdeck.com
Wednesday, May 13, 2020
Video on the Galaxy V VFO Project
This is the second version of this video. I had some technical difficulties getting it to upload in High Definition, but I was able to work it out in this version.
In this video I describe the VFO project, talk about how I made use of the e-bay Galaxy V parts, talk about the circuit (series-tuned Colpitts), conduct some stability tests, and discuss many of the ways a VFO like this one can be useful to the radio amateur.
Thanks to Pete Juliano for inspiring this effort.
Tuesday, May 12, 2020
An Understandable Chip: The LM386
Over the years I have made my distaste for integrated circuits very clear. I've presented them as mysterious little black boxes that don't really belong in our homebrew rigs, rigs that we are building, after all, because we want to avoid the use of MYSTERIOUS BLACK BOXES.
So, I don't use voltage regulator chips -- I use Zener diodes. I prefer analog LC oscillators to AD9850s or Si5351s. And I have repeatedly built discrete component audio amplifiers when most normal people just put an IC AF amplifier in the circuit.
When I built the Q-31 Shortwave AM receiver, I kind of ran out of gas at the end. I wanted to get the receiver going and I didn't want to build yet another discrete AF amp. So I used an LM386.
I rationalized this deviation from cherished values by noting that the discrete AF amplifier circuitry that I was using was remarkably similar to what exists inside the LM386. So that little chip is just as understandable as my discrete component creations. It wasn't REALLY a mysterious black box...
Around this time I found a web site that made me feel mush better about all this. It explains very nicely how the little LM386 does such a great job. It really packs a lot of amplification into a very small package. Here is the web site:
https://www.electrosmash.com/lm386-analysis
Shortly after my transgression, Jenny List over at Hack-A-Day posted a nice piece looking at the inner workings of Op-Amps. Who knows, I may seen be using 741 chips too!
Here is the Hack-A-Day piece:
https://hackaday.com/2020/05/09/an-op-amp-from-the-ground-up/
Saturday, May 9, 2020
Bill Meara Graduates with Honors from James Madison University
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| Deep thoughts where Faraday lectured |
He has been part of the podcast and blog since the beginning: Camera kites, video rockets and crystal radios. Drones and exploding corn starch. The Trivial Electric Motor. Visits to Faraday's lab and Marconi's house. Billy helped me wind toroids at age 2!. He went with me to hamfests in Virginia and in London.
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| Toroid by Billy (at age 2) |
Here are just some of the blog posts in which Billy is a key player: https://soldersmoke.blogspot.com/search?q=Billy
This video demonstrates Billy's early interest in biotechnology:
This video demonstrates Billy's early interest in biotechnology:
And of course, he is the guy who says "Ooo! That's awesome" in all of the podcasts.
Yesterday was a big day: We are very proud of our son Bill Meara who graduated with honors yesterday from James Madison University. Bill earned his Bachelor of Science degree in Biotechnology. In a few weeks he will be heading to Boston where he will start work at a neuroscience research lab of Harvard University.
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| 2020 Virtual Graduation |
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| Billy's mom, sister and dad watching the graduation |
Graduation: Oooo! That's Awesome!
Tuesday, May 5, 2020
Sunday, May 3, 2020
QSO Today -- Episode 300 -- Panel Discussion
Congratulations to Eric Guth, 4Z1UG for reaching episode #300 on his QSO Today podcast. To commemorate the event, Eric organized a panel discussion. It was a real pleasure and honor to participate.
Listen to it here: https://www.qsotoday.com/podcasts/300
Thanks again Eric!
Saturday, May 2, 2020
N6ORS's Hot Mustard Phasing Board. And how Phasing Works.
Keith N6ORS is a prolific homebrewer and a frequent contributor to the SolderSmoke blog. Many of you will remember his MINEX rig. And who can forget his SDR creation, called (by him!) "Satan's Digital Radio"? Well, Keith is at it again, this time working on a phasing rig.
HI Bill,
Its been a while. Lately I've been working on a phasing transceiver73,
A while back I did a little diagram that -- for me -- explains how phasing cancels one of the sidebands. It appears below. I think Keith's board is for the 90 degree audio phase shift. You can see how, by changing the shift from you can affect the degree of sideband suppression. I guess by going from -90 to +90 you could completely switch sidebands.
This diagram shows a direct conversion receiver with the VFO tuned to 7200 kHz. There is a signal at 7202 kHz and another signal at 7199 kHz. In a simple direct conversion receiver, BOTH these signals would produce audio tones in the receiver output. You'd hear both a 2 kHz tone and a 1 kHz tone. Assume you only want to hear the 1 kHz tone resulting from the 7199 kHz signal. Phasing lets you do this. Here's how:
-- First split the VFO signal into its "normal" output and an output that lags by 90 degrees (-90)
-- Consider the output from the top (normal) mixer to be your reference signal.
-- Because of the lag in the VFO signal going to the bottom mixer, the output from the bottom mixer will have the 1 kHz signal 90 degrees ahead of the reference signal (+90) while 2 kHz tone will be 90 degrees behind the reference signals (see "scope view") above. This is a consequence of the mixer math.
-- Now, in the bottom signal path, shift BOTH audio tones by -90 degrees (in relation to the top reference signal). I think this is what Keith's board is doing.
-- With this -90 degree shift, the 1 kHz signal on the bottom path will be IN PHASE with the 1 kHz signal at the top. But the 2 kHz signal in the bottom path will be 180 degrees OUT OF PHASE with the (top) reference signal path.
-- The two signal paths are combined before going to the audio amplifiers. The 1 kHz signal is reinforced while the 2 kHz signal is "nulled out."
The same principle can be used on transmit. Instead of two receive mixers, you have two balanced modulators. Both are putting out upper and lower sidebands. Instead of the VFO you have the carrier oscillator. By using the same phase shifting techniques you can reinforce one of the transmitter's sidebands while nulling out the other.
A Toroid Winder from the Wizard of Wasilla -- Paul KL7FLR
Paul KL7FLR has been sharing tribal knowledge with us for several years now. He recently provided insights on how to tap threads into metal. In 2017 he told us about his Alaskan road-kill microphone. And in the midst of the current quarantine he built this really neat toroid winding tool. Winding coils is often a show-stopper for would-be homebrewers; Paul's device should help then get past this perceived impediment. Thanks Paul!
Paul writes:
A few weeks ago I needed a way of holding a T37-6 toroid to wind an LP filter coil. Being of the fumble fingered crowd I slapped together a quick and dirty holder using a crudely tapered ¼” wooded dowel. As fate would be, I soon needed to wind some other coils of a larger diameter and my wham bam holder wouldn’t do the job. Time to make a holder for more than just one size with the materials I had on hand.
I measured the id of the smallest toroid and the largest toroid I had and plugged them into an online taper calculator. https://www.easycalculation.com/shapes/taper-degree-calculator.php. Calculated taper was 6.65 degrees so I settled on an even 6 degrees with a length of 1 1/2”. The final of the taper was extended to 3”. Using my small 6” metal lathe I set the compound to 6 degrees and chucked up a 4” piece of a ¾” wooden dowel. I would have liked to have an ash, maple or other hardwood dowel but I used what I had on hand. Then I turned the 6 degree taper for 3” until the smallest end was 1/8” making the large end almost ¾”. Some sanding with 320 grit sandpaper followed by some ultra-fine 400 grit made it ready for a coat of clear sealer and a quick stain.
Moving over to the milling machine, I set the 6 degree angle with a 6 degree parallel in the vise. Positioning the mill spindle to the center of the dowel I used a #0 center drill to mill a slot the entire length of the taper to about .015” deep as I didn’t have a 1/32 end mill. This slot also can be accomplished with a rotary tool or a hobby knife and a steady hand.
I had a couple of 6-32 wood brass insert nuts in the hardware bins. Believe I bought these at Lowes and the Hillman part #880546 is what I used. Drilling a 3/16” diameter hole ½” deep I screwed the insert in until it was flush with the bottom of the dowel. My previous toroid holder had a wooden base but it proved to be too light and easily moved around on my bench. I dug out a scrap hunk of ¾” steel about 2.5 inches square. I then drilled a hole through the base using a #27 drill. Now the toroid holder can be mounted on the steel base using a 6-32 machine screw about 1 ¼” long and removed for a different size spindle when necessary. A wood base can also be used with appropriate length wood screw. Be sure to drill a pilot hole large enough in the spindle to prevent from the wood screw from splitting the spindle. A #6 wood screw long enough to pass through the base and into the spindle about ½” would be adequate.
Winding consists of passing the wire up (or down) the slot, lifting the toroid up and rotating slightly and back down on the spindle for the next winding. This has proved to be a very useful fixture when needing to wind some toroid coils.
The picture at the top shows a T-37-6, T50-2 and a T68-2 top to bottom. Will also fit a up to a T-106. Any larger toroids would require a larger spindle to be made.
Enjoyed your YouTube “Quarantined Receiver” and all the doings from Pete.
Paul
KL7FLR
Idaho Homebrew -- Brian KE7LOY
This (above) is a general Shortwave Superhet receiver I built over the winter. I chose to go modular so I could interchange some of the modules and make easy repairs and changes to the circuits. I used discreet components and only 2 integrated circuits. I built a Colpitt's buffered oscillator which is remarkably stable, a Gilbert Cell Double Balanced Mixer, a high pass filter to filter out local AM broadcast station. The IF chain uses an old classic collins 455 khz mechanical filter amplified by a J310 feeding into an MC1350P IC... It's using 2 germanium diodes as a detector feeding into an LM386 output amp. It's very, very selective and sensitive. I added a 455 khz BFO (lower right in pic) the other day to tune in SSB and CW. This has been a fun experiment.
Friday, May 1, 2020
10 Meter Quarantine QSOs near Boston -- KC1FSZ's Peppermint 10
Hi Guys:
I hope all is well. Thanks for the more frequent episodes!
I’ve not submitted anything lately but I’m still doing a lot of building. Over the last few weeks I’ve been working to get myself on 10 meters. There is some good local activity up here in the Boston suburbs on 10. The result of this effort is the next in the Peppermint Line of high-performance radio products for the discerning operator: The Peppermint 10. This rig uses digital VFOs and puts out about 12 watts on a good day. It works in conjunction with a direct-conversion receiver that has been modified for 10 meters. The details are described in the write-up (see link):
73s,
Bruce KC1FSZ
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