Radio Astronomy RFI from Starlink

https://futurism.com/spacex-starlink-satellites-radio-signal-emissions

A Nice Quick HW-101 Restoration Video

 This video is almost enough to get me to work on my old HW-101. 

Pete N6QW has been working on an HW-32A monobander. Some of the info in this video might be applicable. 

Car Talk

The video above is really a lot of fun. 

We are approaching the 20th anniversary of the SolderSmoke Podcast.  Our first upload was August 21, 2005.   This has caused me to reflect a bit on those who are responsible for making our podcast what it is.  So, these guys are definitely among the responsible. 

Wow, MIT grads.  Is Phil W1PJE listening?  

 Dewey, Cheatham & Howe!  Right in the window! 

How computers in cars have killed the joy.  "There is just not a lot to be in love with anymore." 

"The show sounds like the kind of thing you'd hear on a high school PA system."  Indeed. 

Other influences:  Jean Shepherd. HCJB.  Radio Moscow.  More to follow.

Here is their 1999 MIT Commencement Speech:  https://www.youtube.com/watch?v=KWG1Yxoa_Os

Britain's Secret Listeners

Today Hack-A-Day has an unsually good report on Britain's Voluntary Interceptors. I was especially touched by the story of the guy who provided reports while still bedridden from devastating wounds received in World War I. 

https://hackaday.com/2025/06/12/crowdsourcing-sigint-ham-radio-at-war/#more-786810

I've had the video on the SolderSmoke blog several times.  It is so good that it warrants inclusion yet again: 

https://www.youtube.com/watch?v=RwbzV2Jx5Qo&t=228s

That regen looks a lot like the one I bought at the Kempton Park rally (London) so long ago.  I still have it.  And those headphones found in the old "radar" station look a lot like some that I have in my shack today.   And of course there is that HRO dial.  I build a whole receiver around that gem from Armand WA1UQO.  

I thought the comments on the ability to detect the nationality of the enemy operator from his Morse Code "fist" (sending style) was very interesting.  

Three cheers for the Voluntary Interceptors!  

Rick W1DSP's FB SolderSmoke Direct Conversion Receiver -- Exploring the Rabbit Holes

Thanks to Rick W1DSP for sending us his "proof of life" video.  It is indeed alive!  Congratulations Rick!  Welcome to the Hall of Fame!

Rick writes: 

Here's another SS DCR proof of life video. I took a bunch of detours on the way to get here - redesigned the coil former to add a fixed coil (learned openscad), spent a bunch of times on the DCR classics (KK7B, W7EL designs), acquired parts to build the original KK7B DCR, and so on. This is the sort of project that's a perfect excuse to explore all the sorts of rabbit holes we hope to find along the way to completing a project. Thanks for a great project. I'd just like to add that you're building a great community of experimenters. Most excellent, sir! Thanks to Bill & Dean!

Phil W1PJE, Director of MIT's Haystack Observatory, visits SolderSmoke East, Talks Radio with N2CQR and KK4DAS

We were very pleased that Phil W1PJE was able to visit yesterday. Phil is the Director of MIT's Haystack Observatory. He is very knowledgeable on topics related to space and space technology. He is also a member of the SolderSmoke Direct Conversion Receiver Hall of Fame. We talked about the history of the Haystack Observatory, famous antennas (dishes), and about the SolderSmoke Direct Conversion receiver project. It was a lot of fun talking to Phil. We managed to shoot this video with him. Thanks Phil and thanks Dean.

A FIRST! K1OA Contact with N2CQR -- All Homebrew with SolderSmoke Direct Conversion Receivers on Both Ends

At around 0630 EDT on June 7, 2025 I heard K1OA calling CQ on 7030 kHz CW. This was exactly where I had a crystal.  I called him, but he didn't hear me.  I sent him an e-mail.  We tried again -- he heard me calling him and I heard him responding by calling me, but I don't think we succeeded in exchanging signal reports. It was close, but no cigar.  

I had to walk the dog. Scott and I agreed to meet on 7030 kHz at 0730 EDT.  Arggh.  There was a QSO there.  I thought we might have to try to change frequency, but this would have been tough because both of us were crystal controlled on transmit.   Fortunately, the contact on 7030 kHz wrapped up.   Scott called me, I responded, and we were able to exchange signal reports.  I was so excited that I almost forgot to hit the record button on my phone.   But I caught the last minute or so.  See above.  

This was really something.  This really goes to prove what Dean and I have been saying all along:  this receiver is not a toy!  It can be used for real ham radio contacts.  And now we have had these receivers on both ends of a contact.  For transmit, Scott was using a KA4KXX transmitter with about 3 watts output.  I was on my Tuna Tin 2 at about half a watt output.   

Thanks Scott! And thank you Walter!  

A Tale of "Ten Minute Transmitters" and "Tuna Tin Twos": N2CQR Goes Back to CW QRP!

Inspired by K1OA and KA4KXX, I put the SolderSmoke DC receiver to work on the CW portion of 40 meters. At first I used a very (perhaps overly) simple "Ten Minute" transmitter. On June 4, 2025 I worked N2WJW in New Jersey. But the transmitter drifted as it got hot. So I switched to the more robust Tuna Tin 2 (TWO transistors!) and worked W2XS in NY and N9FGC in Indiana on June 5. With both transmitters I was "rock bound" -- crystal controlled. Power out was always less than 200 milliwatts. Antenna was a low to the ground dipole. The receiver was powered by our beloved 9V battery. The transmitter had a second 9V battery. Some observations: First, even if you CAN hear other signals, the different tones allow your brain to seperate them out (this has long been known to CW operators, but might not be readily apparent to newcomers). So even if the DC receiver is broad in frequency response and even though it IS also receiving the other side of zero beat, you can make CW contacts (unless, of course, another station is on a frequency that produces exactly the same tone as the one you are trying to work), even at very low power . Second, you don't always really have to be right on the other station's frequency. Here's why: If he is looking he can see you in his waterfall! So that SDR waterfall is now a friend to crystal-controlled HDR operators. Who would have thought? Above is a picture of the my station with the Ten Minute transmitter. See the notes I wrote on the QSO with N2WJW.

Ten Minute Transmitter (the gray thing is a CW key)

Direct Conversion Receiver

Tuna Tin 2 that replaced the Ten Minute Transmitter

Note battery and crystal

Alan Wolke W2AEW's Build of the SolderSmoke Direct Conversion Receiver

We were already very proud to put Alan Wolke W2AEW in our Hall of Fame.  But Alan put icing on the cake this morning by making his own video about his build, along with some pre-CME video of the machine inhaling CW and SSB (see above).  The SSB is DX, from France.  FB Alan, thanks.  

My only comment to Alan was on the frequency readout.  I noted that many builders had resorted to San Jian PLJ frequency counters.  A few others had done what he did and used the frequency readout feature of their Tiny Spectrum Analyzers.  I told him that at first I had gone very low tech.  It was in fact, quite barbaric.   Check it out: 

I think it is kind of low-tech cool.  I am a bit disappointed that none of the builders have done anything similar.  Mark KI5SRY came the closest, but his solution was relatively spophisticated.  Look, it is not to late.  Get out those index cards and calibrate those screws!  Send in pictures or videos.  

Ashish N6ASD's Beautiful SolderSmoke Direct Conversion Receiver -- Built in Bangalore -- "This was such a fun project. This was my first direct conversion build, and I learned a lot along the way."

Ashish N6ASD is a really good guy.  We started watching his projects when he was in San Francisco.  He does a lot of fundamental radio building.  And he is a friend of Homebrew Hero Frank Harris K0IYE. 

When I spotted a "thumbs up" from an N6ASD on the SolderSmoke Discord channel, I knew that we would soon have yet another Bangalore Direct Conversion Receiver.  Ashish has been in contact with both Farhan and Ramakrishnan.  FB. 

Ashish writes:  I finally finished building the receiver! This was such a fun project. This was my first direct conversion build, and I learned a lot along the way. The biggest challenge was finding stable capacitors for the oscillator. In my first attempt, I used whatever I had in my junk box, but those capacitors drifted all over the place. Mica caps seemed expensive and difficult to get in Bangalore. I ended up buying surface-mount NP0 capacitors instead. Soldering them was a hassle, but they are much cheaper and easier to get here. Next step will be more mods and experimentation! The first improvement will be in the BPF. I will replace the regular ceramic caps with NP0 caps and re-tune it.

Here is Ashish's receiver inhaling CW:   

Congratulations Ashish -- Welcome to the Hall of Fame! 

Ashish N6ASD

The resemblance between Ashih's photo and the famous

1818 painting by Caspar David Friedrich is completely coincidental,  

but quite remarkable. 

https://en.wikipedia.org/wiki/Wanderer_above_the_Sea_of_Fog

 

Not a Toy! K1OA Making Contacts with the SolderSmoke Direct Conversion Receiver and a KA4KXX Transmitter

This goes to prove what we have been saying all along:  this receiver is not a toy!  It is capable of operating as part of a real 2-way ham radio station. Hall of Fame member Scott K1OA has paired his receiver up with a Merry Christmas transmitter designed by Walter KA4KXX and has been making CW contacts with it (see above).  Walter supplied the crystal and many of the needed parts.  Scott has already worked WA9RNE, N4HAY and W3RJ, and has tried making contact with Walter but no luck yet. He has gotten RBN reports from Germany and New Zealand. All that with just 3 watts.

This is not the first time this receiver has been out to use.   I made one contact with it using a "Ten Minute" QRPp transmitter that I had intended only to use for test purposes: 

https://soldersmoke.blogspot.com/2023/02/first-qso-with-high-school-receiver-100.html 

HoF member Aaron ZL1AUN used his receiver with an SSB transmitter to make contact using his receiver:

https://soldersmoke.blogspot.com/2025/02/soldersmoke-direct-conversion-receiver_23.html  We understand Aaron's article about the receiver has been published in "Break-In" magazine -- we hope to get a copy (electronic would be fine!) 

And who can forget HoF member Nate KA1MUQ who turned his "frying pan"  direct conversion receiver into a double sideband transceiver and used it to make phone contact with Idaho from California: 

https://soldersmoke.blogspot.com/2025/03/nate-ka1muq-turns-his-frying-pan-dc.html 

If anyone is aware of other contacts made using this receiver, please let me know.  

Hiss, Filters, QRM, and Hearing Loss: Do we need AF filters in direct conversion receivers?

L6 is the 88mH toroid

Messages on Discord about the need to knock down higher frequency audio response in the SolderSmoke direct conversion receiver got me thinking.

I agree with Rick Campbell and others on the benefits of hearing a "wide open" direct conversion receiver. But Rick and others have built DC receivers with 3 kHz low pass AF filters. This made me ask myself a question: Is an audio filter in a direct conversion receiver a good idea?

And I started wondering if perhaps I was being too dismissive about the complaints about high frequency audio -- I had been attributing them to newcomers who were just unaccostomed to radio noise or "static." But maybe there was more to it than that. Maybe a big part of the problem was in my head, specifically in my ears. So this morning I did an experiment. I took an online hearing test. First, without my hearing aids: As expected, it showed significant high frequency loss. (It was as if the US Army had installed a 3 kHz audio low pass filter in my head!) Then I put my hearing aids in and retook the test: This time I passed the test and showed no loss. I then listened to the DC receiver with my hearing aids in. Now I could hear what builders on the Discord server were commenting on: I could hear higher frequency hiss, and, more importantly, stations that were producing 4-5 kHz sounds on my speaker were audible and annoying.

So I went back to Wes Hayward's November 1968 QST article. In his receiver, he has a low pass AF filter using an 88 MILLIHenry coil and a couple of capacitors to ground. I had a few of the coils (given to me years ago by a NOVA QRP club member) so I built it. With my hearing aids in, I noticed an immediate improvement. I then did what one of the Discord builders did and put the filter in with a switch that would let me make "with and without" comparisons. The filter definitely cuts down on any AF above about 3.5 kHz. And it doesn't seem to do damage to the desired signal. This is useful. I left the W7EL diplexer in the circuit.

This filter won't solve the image or "opposite sideband" problem inherent to simple DC receivers, but it will help with signals or noise that are producing tones above about 3.5 kHz in the receiver. I think this is especially important in countries in which there is a lot of SSB crowding on 40 meters. The UK, for example, has an allocation from 7.0 to 7.2 MHz. In the US we go from 7.0 to 7.3 MHz. That is a big difference.

So the answer is probably yes, an AF filter in a direct conversion receiver is probably a good idea, especially if you can switch the filter out of the receiver. You can live without these filters. Not having the filter keeps the receiver very simple, and lets it sound really great. But having the filter in there does help reduce interference and high frequency hiss. So I think this is a useful add-on mod for builders who see a need to cut down on the kind of interference that a lack of this filter causes.

In 2019 W7ZOI noted: "Another unusual element is the 88 mH toroid used in the audio low pass filter at the detector output. A viable substitute would be a 100 mH inductor with radial leads. The muRata 19R107C (from Mouser) should work. Bourns also offers a variety of similar parts."