100 Years Ago: Hugo Gernsback on "An Amazing Art"

I like the art work in the header.  I like the reference to "the radio art."  I like that he refers in the first half of the piece to "the radio tribe" -- that would be us!  And this reminds me of "tribal knowledge."  He also talks about rigs "scattered across the table" -- Al Fresco!  

In the second half of the piece he veers off into a kind of weird call for standardization and ladies hats.   But the first half is good, and it is interesting to take a look at the hobby 100 years ago.  Click on the image for an easier read. 

The Ceramic Spurs (not a rock group)

Paul Taylor VK3HN's magnificent AM receiver was the inspiration for my Quarantine-31 Shortwave Broadcast receiver.  Like Paul I decided to make use of ceramic filters at 455 kHz for selectivity.  I started with the +/- 3 kHz filters that Paul used, but I found them kind of narrow for SW listening.  So I went with some wider ceramic filters that Bruce KK0S had sent me.  But I misread the specs that Bruce sent.  I thought they were 10 kHz wide filters. I realized later that they were +/- 10 kHz -- really twice as wide as I needed.  So I went back to Mini-Kits in Australia and got some +/- 6 kHz filters.  12 kc wide should be just about right, I thought. 

The bandwidth was right, but I started noticing a problem:  I could hear strong SW broadcast stations at two places on my dial.  This brought to mind an admonition from R.A Penfold, author of "Short Wave Superhet Receiver Construction" (1991 Babani Publications).   He advised keeping a few standard 455 kc IF cans in the circuit because, he warned, the ceramic filters have spurious responses, spurs that the IF cans can help knock down.  

Penfold was right.  Look at the filter response curve on the right (above).  There is a nasty spur at around 640 kHz.   This was the cause of my problem. Here is why: 

Suppose I was tuning Radio Marti's big signal on 9805 kc.  My VFO would be running at 9350 kc. 

9805-9350=455.  Great, but... 

With that spur at 640 kc, I could tune down to 9620 kc on my dial.  My VFO would be running at 9165 kc. 

9805-9165=640.  Bad.   That 640 kc difference product would make it through to my detector and AF amp.  I'd have Radio Marti showing up in two places.  I didn't like this. 

I thought about putting a series LC circuit tuned to 640 kc at the output of the ceramic filter.  This looked like a possible solution, but on the bench it looked like I would have trouble getting a circuit of sufficiently high Q.  

So rummaging around in my junk box I found an old Murata CFM455B filter.  This filter is quite broad, but it does not have the spur at 640 kc.  I could use it as a kind of roofing filter just ahead of the +/- 6 kHz filter.  Putting it there would allow me to avoid having to build additional matching circuits for the 455B filter.  

+/-6kc filter upper left,  455B wide filter to the lover right. 

I'm happy to report that this fix works.   The 6 kc filter provides the needed selectivity, and the broader 455B filter knocks down the 640 kc spur. 

Beware the Ceramic Spurs!  

Q-31 with can for first IF amps and filters open

A Backyard Pandemic Field Day in France (Smoke Released!)

Thank you Alain! 

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

Hello Pete and Bill,

As you know I am a great fan of your blogs. The fields days are not usual here but because our both countries have been hard hit by the Covid I felt good to participate in this kind of (solo) activity.

My wife Patricia shot 2 pictures for you.

I did some QSO with my callsign followed by FD, but in my enthusiasm I pushed a bit the pressure on my small TX and the PA Mosfet went promptly to the sky...

As you will see, even my dog Guerlain (no callsign) participated...

Hope that you enjoyed a great FD.

Take care my friends.

73 Alain F4IET

SolderSmoke Patreon -- What We Will Do with the Money

Become a Patron! 

I mentioned our Patreon fund-raising effort in Podcast #223.  We immediately got a number of new sponsors.  Thanks!  We also got a question:  "Hey Bill, what are you going to do with all that money?" In the spirit of SolderSmoke full transparency, I will attempt to answer that inquiry right here and now: 

All funds will be used at the discretion of SolderSmoke management.  

Possible (likely) uses include: 

-- Buying air time on shortwave broadcast stations so that the SolderSmoke podcast can be transmitted over the airwaves. We dream of stealing listeners from Brother Stair.   

-- Computers.   From time to time we need to upgrade. This 486 machine is getting kind of rickety. 

-- Paying fees to our internet service providers and to the server that hosts our podcast. 

-- Contributing to worthy charitable causes, including the Color Burst Liberation Army (CBLA), and the Constructor Crusaders.  

-- Buying audio gear we use in the podcast like the really cool microphones that have DRAMATICALLY improved our audio.  No more baby-wipe pop filters for us! 

-- Legal fees to the law firm of Dewey, Cheatam and Howe to fend off law suits, many of which are related to our obstinate use of 60/40 solder, and to our occasional use of images that SOME PEOPLE find offensive.   We also need to pay legal fees to fight our long-contemplated expulsions from the QRP Hall of Fame (Pete is especially vulnerable here). 

-- Magazine subscriptions (to those few remaining publications that have not pissed us off ).  

-- Buying stuff we use in video production (cameras, tripods, lights etc.) 

-- Further development of the SolderSmoke 401k Retirement fund.  We currently invest in Drake 2-Bs, SSDRA books, Hallicrafters S-38Es, 3579 kc crystals, and other items sure to rise in value over time. 

-- Buying gear we will talk about on the podcast or in videos (like the NanoVNA).  

-- Parts.  Si5351s and Raspberry Pi's for Pete.  2N3904s and J-310s for Bill.  

-- A new effort to assist electronics manufacturers in China with product name selection.  "Mean Well" is just not a good name for a voltage regulator.  And "FeelTech" does not bring to mind a signal generator.   For a fee, we can help!  

-- Travel.  If this ever becomes possible again, we need to get to India to meet up with Farhan.  This will undoubtedly result in some awesome podcast/blog/video material.   We also contemplate trips to the UK, Italy, Australia, China and New Zealand.  But we still probably won't go to Dayton. 

-- Buying miscellaneous tools, test gear, books, solder, rosin etc. to be used in the podcast, the blog, and in video production. 

-- Buying stuff for carefully selected new homebrewers (people who will not sell the stuff we give them and then use the money to buy Baofengs). 

-- A new Baofeng buy-back program.  You know, like for assault rifles, but for VHF/UHF walkie-talkies instead. 

We seek your input!  What else should we do with the money?  

Become a Patron!

DK7IH Improves his Shirt-Pocket Transceiver

More great stuff from Peter DK7IH.   He recently made some improvements to his "Shirt-Pocket SSB Transceiver.  On his blog he explains why he made the changes.  Note the Si5351 that is in there now.  I liked the 1 cm square T/R unit that Peter wrapped in heat shrink tubing. He also provides a really nice description of how to do front panel labeling with a laser printer.

Here it is: https://radiotransmitter.wordpress.com/2020/06/28/re-engineering-my-1st-shirt-pocket-transceiver/

Thanks Peter!