IMD in Transmitters -- Splatter? Or Signal Strength?

https://www.newsvhf.com/conf2024/PresPapers/WA1MBA-IMD_in_Transmitters.pdf

Here is a good (and very recent) article on IMD ("splatter") produced in transmitters. The focus is on VHF, but much of this is relevant to HF operators.  I found the footnotes on the ARRL "Clean Signal Initiative" to be worrisome.  They seem to just be assuming that all ham operators will be using commercial gear, and the "OEM" needs to be made to meet certain standards. This seems to leave the homebrewer out in the cold.  I can see where someday soon, the "standards" will exceed the capability of analog homebrewers.  That would be bad.  

The role that signal strength plays in the perception of "splatter" is often misunderstood by the "waterfall police."  We often we hear some irate waterfall policeman screaming that,  "You are 40 over and far too wide."   Here is a good quote from the article on this point: 

"If you have a calibrated spectrum display (as many SDR’s are these days), you can directly measure the level difference in dB. If it is 30 dB or more, then it could be an acceptably “clean signal”, even if it is bothersome. Most ham voice communication is conducted with less than 30 dB signal/noise, and in that case the unwanted IMD is buried in the noise."

And even in a low noise environment,  if the signal is 40 db over S9. that would mean the signal PEP is at -33dbm.  If the IMD products are 46 db down from the signal peak, that means your IMD products are -79 dbm.  That is S-8!   That signal will look quite wide in the waterfall, but it would be within FCC specs, right? The problem here is not so much distortion, as signal strength.  And let's remember that "legal limit" is usually a misnomer:  FCC regs require hams to use the minimum power necessary, not 1.5 kW on every single QSO. 

The Surprising Difficulty of Analog Circuit Chip Design -- AI to the Rescue?

https://www.youtube.com/watch?v=lNypq1XuZRo

Really interesting.  Why the design of the analog portions of chips is so much harder than the design of the digital portions.  

Great channel. 

Sony and the Transistor

 https://www.youtube.com/watch?v=7pi9k5n7Wrw

I found the comment about Sony's belief that NPN transistors are superior to PNP very interesting. 

IMD and Splatter

 

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/hr/1988/10/page71/index.html

I think the point I was trying to make about the influence of signal strength is here:  

Referring to fig. 1C, note the high level of rf at the 3rd order level - typically 36-dB down. Consequently, there will be rf energy outside the normal 23 kHz passband that will be only 36-dB below the carrier peaks, or about one four-thousandth of the peak power. Not bad if the station is only 25-30 dB out of the noise, but very objectionable if it's 40-60 dB out of the noise.

I think it is supposed to read "2-3 kHz passband" vice "23kHz passband."

I guess the point is that QRP levels of operation can hide a host of ills.   IMD ills.  This makes me wonder about the cleanliness of my own signals.   I will have to do some more careful measurements. 

Ham Radio in the 1970s (and earlier, with some cool Jazz). What favorite rigs do you see?

Rogier PA1ZZ sent me this today.  I think I may have seen pieces of it before, but this restoration 

is really nice.  But ham radio seems to have been a lot cooler in California.  I don't remember it being so socially advantageous on the East Coast.   See Dilbert cartoon below. 

So many memories: 

-- The video opens with someone working on a QF-1 Q multipliers.  We have destroyed so many of these relics, in pursuit of the variable capacitors (which turn out to be not so good). 

-- A Drake 2-B on Field Day. 

-- An HT-37 in a shack.

--What looks like an HW-32a in a mobile rig. 

-- Maybe an HW-101. 

--  A BC-348. 

-- The ATV station with lots of homebrew gear was very cool. 

-- I also liked the single THERMATRON homebrew CW rig made from an old TV.  FB. 

-- The CW used in the video was all pretty good.  There was a lot of chirp.  This, of course, adds character to a signal.  FB.

After the video, they take a walk down memory lane, looking at ham radio magazines with some cool jazz playing in the background.  I saw a Swan 240 and a D-104.  The debauchery of the 1970s was evident on the magazine covers.  Even QST seemed to be caught up in this.  Check out the August 1975 cover of QST.  

Anyway, this video was a lot of fun.  Thanks Rogier!  

What favorite rigs do you see?   Make note of them in the comments. 

This video and the Dilbert cartoon reminded me of a discussion we had many years ago about THE KNACK: 

https://soldersmoke.blogspot.com/2008/11/cry-for-help-soldersmoke-responds.html

Excellent New Video from Grayson KJ7UM on his Thermatron version of the Michigan Mighty Mite

Here is a really wonderful video from Grayson Evans, KJ7UM, author of Hollow-State Design for the Radio Amateur.  

I really loved this video.  Throughout we see Grayson's sense of humor.  Early on he explains the differences between a tube (what remains from a roll of paper towell), a valve (like the plumbers use) and a THERMATRON (like a 6146).  Grayson is the inventor of the word Thermatron.  We should all pledge to use it whenever possible. 

Grayson's humor also shows up when describing the parts acquistion process for the Thermatron Michigan Mighty Mite.  He puls out a coil (a huge coil) and laments that it is not -- despite its large size -- sufficiently inductive. 

There are wonderful shout outs to SolderSmoke, to Electric Radio, to the Color Burst Liberation Army, to Pete Juliano,  and to Rex Harper.  

Grayson describes the utility of Rex Harper's Thermatron ME pads.  

During the video, Grayson actually builds the Thermatron MMM.  In under 2 minutes!  He then experiences the Joy Of Oscillation, or JOO as it has come to be known.  OM needs a contact -- listen for him on 3579.  He is calling CQ.  

Grayson talks about his book, Hollow-State Design.  I have a copy with me here at SolderSmoke Shack South in the Dominican Republic.  Great stuff.   The above link takes you to Lulu, where you can order the book.  You can also get it from Electric Radio Magazine here: https://www.ermag.com/product-category/books/

Thank you Grayson for bringing us this video, and so much more over the years.  And for giving us the very useful and fun word:  THERMATRON!  

Who can tell us more about Lovelock's homebrew shortwave radio?

"Three years earlier, Lovelock had listened on his homemade shortwave radio in Finchley to the 'beep, beep, beep' transmission of the USSR’s Sputnik, the first satellite that humanity had put into orbit. Now he was playing with the super powers."

From: https://www.theguardian.com/environment/article/2024/sep/05/gaia-theory-born-of-secret-love-affair-james-lovelock

A bit of a soap opera, but the radio question is, I think,  interesting. 

CuriousMarc Visits Cape Canaveral -- Lots of Space History (and some ham gear)

I like all the CuriousMarc videos, but I especially liked this one. Marc and company visited some of the very early launch sites and bunkers at Cape Canaveral.  If you thought Apollo tech was crude, take a look back at what they used in Mercury and Gemini.  Wow.  

I spotted two ham radio receivers.   In the first bunker at 10 minutes 28 seconds we see an old National HRO Sixty with the classic HRO dial, much like the one given to me by Armand WA1UQO. (Thanks again Armand!) Note how they attribute one of the early launch disasaters to two diodes in the power supply that shorted due to launch vibration.  I hate it when that happens.  

In the second bunker we see a Hammarlund HQ-140 at 19 minutes 7 seconds.  This was apparently being used as a Frequency Standard (or maybe a time standard?) perhaps receiving WWV at 10 MHz.  I note that the frequency knob shows it set for the AM broadcast band... 

How to Homebrew your own Transistors

No store-bought transistors for these guys -- they homebrew their own point contact transistors using a bit of Germanium from a diode.  This makes me feel like such an appliance operator.   

This video is in Polish, but The Knack is a universal language, and this guy obviously speaks it.  Turn on captions, then opt for auto-translate to English.  You will then get English subtitles and Bob will be your uncle.  

I really liked this one.  This fellow has obviously DONE this;  his video is filled with both practical tips and theoretical explanations.   He talks about the virtues of beeswax, and about how to borrow red nail polish to mark the collector lead.  FB. 

Here's the channel:  https://www.youtube.com/@Marcin_Marciniak

In their next episode they promise to build a radio receiver using the homebrew transistors.  That'll be great. 

Thanks to Marcin and company, and to Jenny List of Hack-A-Day who alerted us to this. 

Marcin is a ham  -- SP5XMI:  https://trafficlist.altervista.org/radio-officer-friend/marcin-marciniak/

But who is the fellow who built the homebrew transistor? 

Mr. Carlson Makes a Thermatron Power Supply for a BC-348

When I was 14, I had to make a power supply for a Heath HW-32A.   Mine ended up working, but it was nowhere near as nice as Mr. Carlson's BC-348 supply (shown in the video above).  I didn't have a sand blaster, nor a drill press, nor much of anything else, really.  

But hey, don't real boatanchor hams use Greenlee chassis punches?  What's with the drill press and the hole saws? 

Note that Mr. C takes care to make sure that the rectifier tube is in the proper angle FOR OPTIMAL VIEWING.  That's some serious attention to detail OM.  And whoa, DELICATE SURFACE MASKING TAPE from 3M?  Respect!  Also, era-specific looming material. 

His point about the importance of the cardboard washers in the power transformer was really useful.  I hadn't thought about that. 

Here are the two previous BC-348 videos: 

https://www.youtube.com/watch?v=nX87kwSshZ8

https://www.youtube.com/watch?v=Zqe6CBe0iGs

Thanks Paul! 

SolderSmoke Quiz Question: Who is the actor in this Bell Labs video?

He appears at 8 minutes, 17 seconds.  And he is somehow in the YouTube title frame.  I think I know who it is.  Any ideas?  (DON'T LOOK AT THE COMMENTS!) 

 

"Matter Waves" -- A 1961 Bell Labs Film

I continue to mine the AT&T video archive.  Here's a really wonderful 1961 film showing how particles really are waves also.   The simplicity of the gear that the Bell Labs folks used to demonstrate this is really admirable.  I would love to see the preceding film (the one that shows how light waves are really also particles).