Update from KK4DAS on the SolderSmoke Direct Conversion Challenge: BP Filter Added to Circuitry -- Full Video on BP Filter Soon

Dean now has the PTO, the Diode Ring, and now the 40 meter bandpass filter.  Dean fires up his signal generator and, using his 'scope we see audio coming out of the mixer.  FB.  

Dean says he will have the complete build video for this stage soon.  Thanks Dean. 

 

Radio Antenna Fundamentals Part 1 -- 1947 USAF Film

Lots of good info in this 1947 film.  But... At the end they say that an impedance mismatch between the line and the antenna will result in the loss of radiated power.  Is that really true?  This seems to lead to the obsession that many hams have with an SWR of 1:1.  If some power is reflected due to the mismatch, where does that power go?  And what if you put a transmatch at the junction of the transmitter and, say, an open wire feedline.  You could match the antenna system perfectly to the 50 ohms that your transmitter is looking for.  But the mismatch between antenna and feedline would remain, right?   

Video of images and Data Stream: Huygens Probe Parachuting onto Titan

This happened back in 2005, but I saw this video for the first time this morning.  I really like the display.  I frequently see Titan next to Saturn with the 6 inch reflector that Elisa got me. 

And I like parachutes. 

Diode Ring VFO Part II: How Much LO into a Diode Ring?

Last week we were trying to determine how much LO injection we really need in the SolderSmoke Direct-Conversion receiver.  The answer seemed to be "enough to turn the diodes in the diode ring on and off."  Ok, but this brought us to the question of how far we should go with this.  Does it make sense to go for more LO signal? If so, why? And how much more?   Todd VE7BPO offered a very thoughtful comment.  He pointed out that for a simple receiver like this, turning the diodes on and off would probably be sufficient.  Sometimes we hear 7 dbm, others say 10 dbm, or even 0 dbm.  But what is the logic that underpins these figures?   Solid State Design for the Radio Amateur (SSDRA) provides the answer on page 120.  See above.  

With a diode ring (or other switching mixer) you want the LO (VFO or PTO) to be the signal that is switching the diodes  You do not want the incoming RF signal to also be strong enough to switch the diodes.  Having the RF do this would result in something of a mess at the output.  

If you have a weak LO signal going into the mixer, it might on peaks reach the level of turning the diodes on.  You will get some mixing action.  But as the SSDRA paragraph indicates, during much of the LO cycle the diodes will not be switched on.  And they won't be firmly turned off either.   A strong RF signal could come in, add to the LO voltage, and switch the diodes.  That would not be good. 

So if you put a strong LO signal in there, on half the cycle that signal will be turning two of the diodes on.  But on the other half of the signal, that same LO signal will bereversed in polarity,  turning those same diodes off.  Hard off.  Definitively off.  It would take one very strong RF signal to overcome the reverse bias signal put on those two diodes by that LO voltage.  That is the advantage of a stronger LO signal.  

 

Other Workshops: Making The World's Smallest Motor

When I watched this very cool video, I thought of all those hams who complain so bitterly about how difficult it is to wind a toriod on a T-50 core. 

Thanks to Hack-A-Day for alerting us to this. 

 

First 10 Meter AM Contact from Hi7/N2CQR

I threw this in the bag on the way to the DR, almost as an afterthought.  But I am glad I did.  Today, watching reports on my 10 meter CW beacon (Mike WN2A provided the keyer),  I noticed that my signal was unusually strong.  At W3POA I was 7 db above the noise.  At DF2CK I was 4 db above the noise.  So I switched to the 10 meter AM rig (which is a converted GE brand CB rig) and worked John G3YPZ (see video above).   I was running about 5 watts to a quarter wave vertical.  But the signal reached the UK. 

Here are some details on my rig: 

https://soldersmoke.blogspot.com/2025/01/looking-for-contacts-on-10-meter-am.html

And https://soldersmoke.blogspot.com/2023/11/bill-n2cqr-goes-citizen-band.html

Thanks John!  

Fireball (Meteor) Over the Dominican Republic

Click on the link below to see the video

https://www.tiktok.com/@william.de.jesus01/video/7464040455185993002

I had been telling Mike WN2A how I had put a little red LED on my beacon (he gave me the keying hardware) and that I was hoping to put the LED in the window of my 7th floor shack.  I want it to serve as a kind of CW "lighthouse." We are, after all, close to the ocean.  I thought it would be cool.  Last night, soon after sunset, Elisa and I went out to walk the dog and to look a my little light.  

Well, as expected my little light was too small.  But HOLY COW,  it had us looking in exactly the right direction at exactly the right moment.  At 7:09 pm on January 25, 2025 a very bright, green, long-lasting fireball streaked across the sky from North to South (the guy in the clip above got the direction wrong).  It was throwing off fragments.  One kid in the neighborhood saw it.  And soon Instagram lit up (!) with reports and videos.  I filed a report with the International Meteor Organization: https://fireball.imo.net/members/imo_view/event/2025/516  It was all very cool.  The tiktok clip (above) has a collection of some of the best shots.  Just click on the link below the picture.  

I hadn't seen one of these since March 1995 (I was in the Dominican Republic then too!):  

7 MARCH 95 EVENING: POSTED ON CIS:

Also observed a pretty spectacular fireball in the North (near Polaris) at about 2330. So bright I thought it was a skyrocket. Very slow moving looking like pieces falling off it.

SolderSmoke Direct Conversion Challenge The Mixer and Diplexer

SolderSmoke Challenge – Direct Conversion Receiver – the Mixer

 

The mixer is the heart of the direct conversion receiver.  It’s the circuit that makes a receiver a receiver.  It takes the RF from the antenna and mixes it with the local oscillator to extract the audio.  In this video, Dean, KK4DAS walks us through the design, build and testing of the double balanced diode ring mixer we chose for the SolderSmoke Challenge DCR.  He also explores some of the myths, legends, and lore around mixer design.  If you are not yet convinced, we can make an effective receiver with just four simple boards you definitely want to watch this vido to the end. Mixers have been a passion (some say obsession) of mine for a long time.  If you search for “mixer” on the SolderSmoke blog you will find many postings over the years.   Whenever I want to learn more about some RF circuit or other I always turn to Alan Wolke, W2AEW’s excellent YouTube video series.   In the video linked below Alan does an excellent job of explaining mixer theory and demonstrating how the switching action of the diodes produces the sum and difference frequencies.

 

Related links:

 

Alan Wolke, W2AEW - YouTube Video #167:

How a Diode Ring Mixer works | Mixer operation theory and measurement

https://youtu.be/junuEwmQVQ8?si=zinwuz9FcBDbUXM6

 

SolderSmoke Blog on Mixers:

https://soldersmoke.blogspot.com/2022/10/how-diode-ring-multiplies-by-1-and-1.html

 

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

 

SolderSmoke YouTube channel:

https://www.youtube.com/@soldersmoke

 

SolderSmoke blog DCR posts:

https://soldersmoke.blogspot.com/search/label/TJ%20DC%20RX

 

 

A Tale of Woe from Mike WU2D, PLUS: The Importance of Band Noise

It was so cool to watch master homebrewer Mike WU2D candidly describe his error (tale of woe) made while building the Simple X Super receiver.  

It was also great to see his joy in hearing the band noise.  Watch his glee as the noise jumps up when he connects the antenna.  "That's the good stuff!"  Indeed it is.  So many younger builders see noise -- all noise -- as a bug not a feature.  Mike obviously sees it as a feature:  Thunderstorms in Brazil!  The weed-whacker down the street!  Remants of the Big Bang!  Hearing this stuff lets us know that the machine we have built is alive, and is inhaling the universe.  

Thanks Mike. https://www.youtube.com/watch?v=T_Mz9HljCys

 

SolderSmoke Direct Conversion Receiver Challenge -- Soldering!

The DCR challenge is going well, and we have several builders making good progress.  We noticed that some first-time builders are having a little trouble with soldering. Cold or weak solder joints are the bane of the of the homebrew builder’s existence.   It happens to all of us.  A board that was working fine suddenly is not working – you poke around and touch some part and the board springs to life – you just found a cold solder joint.  Dean, KK4DAS put together a short bonus video just on soldering.  He covers the tools you need for a basic soldering station, and step-by-step instructions for reliable soldering Manhattan Style.

No Bunching Up! It is Possible to Achieve Dial Linearity (and Stability) with an LC VFO

One of the major complaints about LC VFOs is that they allegedly cause "non-linear tuning."  Essentially, this complaint claims that you will inevitably end up with your frequencies all "bunched up" at one end of the tuning range, with frequencies greatly "spread out" at the other end. BUT WE HAVE FOUND THAT THIS IS NOT NECESARILY TRUE.  With a bit of careful design work, you can avoid the dreaded "bunching up."  I have used the calculator in Bob's Electron Bunker to DESIGN VFOs that do not "bunch up" the frequencies.  

Recently, Mike WU2D built a version of the Simple X Super receiver.  It has a VFO in the 5 - 6 MHz range.  And guess what?  There is NO bunching up of frequencies. As proof, I present the tuning dial that Mike made for his completed receiver.  See above.  Note the nice linear tuning.   

So you see, success in this area is possible -- all it takes is some careful design work. 

Similar results are possible with the other major allegation about LC VFOs:  That they are inherently and irreparbly unstable.  Proponents of this theory would have you believe that only by the use of an Si5351 (or something similarly digital) is stability possible.  Again, NOT TRUE!  It is possible to make LC oscillators that are stable.  All it takes is careful design and good construction practices. 

SolderSmoke Direct Conversion Receiver Project -- Video #2 -- Building the PTO/VFO

The response to the SolderSmoke DCR challenge has been terrific -with nearly 7,000 views of the first episode!  Thanks so much for checking it out.  The goal is to convince you that you can build your own receiver and then go get you started on Homebrew ham radio.  We already have confirmation that it can be done!  Congratulations to Peter, VK3PTM and Matthew, KY4EOD who have both completed the receiver.  The boards look good and, even better, they sound great.   Videos and descriptions are here on the blog and on the SolderSmoke Discord sever.   Speaking of the Discord server, we already have a very robust conversation going,  It’s a great place to give feedback and to get your questions answered. Builders are helping builders and we at SolderSmoke are trying to answer as many of your questions as we can.  This is a beginner’s project, so all are welcome.

 

In episode 2 of the SolderSmoke Direct Conversion Receiver challenge we tackle the PTO.  We discuss a bit of the theory, walk through the schematic, and take you step-by-step through building and testing the oscillator and buffert.  By the time we are done we will have achieved JOO!  (the Joy of Oscillation).  And when you build it you will be 1/4^th of the way to having build your own 40 meter receiver.

 

 

Links:

 

Join the discussion - SolderSmoke Discord Server

https://discord.gg/XMScV9HT

 

Documentation on Hackaday

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

 

SolderSmoke YouTube channel

https://www.youtube.com/@soldersmoke

 

SolderSmoke blog

https://soldersmoke.blogspot.com/search/label/TJ%20DC%20RX