Sideband Inversion

Joel Hallas, W1ZR, (aka "The Doctor") has an especially good column in QST this month.   He takes on a topic that has confused (and re-confused!) many of us: sideband inversion.  Simply put, if you have a single sideband signal, and you put it through a mixer, depending on the frequencies involved and on whether you take the sum or the difference product of the mixer,  the sideband may or may not get INVERTED!   You could start out with an UPPER sideband signal coming out of your sideband generator, then, after you mix it with your VFO (or Si5351!) you end up with a LOWER sideband signal.  This can be quite an unpleasant surprise.

Joel gives us a good rule for remembering when this will happen: 

"Sideband reversal occurs in mixing only  if the signal with the modulation is subtracted from the signal that isn't modulated."   

Words to live by my friends.  Words to live by.     

The confusion on this topic often arises in discussions of the old scheme of using a 5 MHz, 9 MHz filter/VFO combination to generate LSB on 75 meters and USB on 20 meters.  This is very convenient, but you need to remember Joel's rule to get this scheme right!  If you start out with a sideband generator putting out UPPER sideband at 5 MHz. and mix it with a VFO running at 8.5 -- 9.5 MHz,  for 20 meters you will take the SUM of the two frequencies.  So no sideband inversion.  You will be happily on 20 meter USB (the mode used on that band).   For 75 meters you will be SUBTRACTING the SIGNAL WITH THE MODULATION (5 MHz) from the SIGNAL WITHOUT THE MODULATION (8.5-9.5 MHz).  So, following Joel's rule you WILL get sideband inversion.  Here you will be on 75 meter LOWER sideband (the mode used on that band). 

It is easy to get confused on this.  I got confused when Steve Smith sent me a 9 MHz filter out of an old Yaesu.  I had visions of using the old 9 MHz 5 MHz scheme.  But no.... With a 9 MHz sideband generator, you can get on both 75 and 20 with a VFO running at 5 to 5.5 MHz, but you won't get the nice sideband inversion situation described above because with neither band will you be subtracting the signal with modulation (9 MHz) FROM the signal without modulation (5-5.5 MHz).

It was very nice that Joel admitted to falling victim to this kind of confusion himself in a column he wrote years ago. 

Thanks Joel!  


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Drake Dongle Derring-Do -- 2B goes SDR (video)

Here I take my Drake 2B  -- arguably the quintessential Hardware Defined Radio -- and connect its first Intermediate Frequency circuitry to an RTL-SDR Dongle, allowing me to digitally process, filter, and display (panoramically!) the signals being inhaled by the ancient receiver.  Another cool tech twist:   To get at the 455 kHz IF signal I use the "Q-Multiplier" jack on the back of the receiver.  This connector was put there to allow for the use of a selectivity enhancing regenerative stage.  So I'm using that connector for a similar purpose, but using technology that wasn't even being dreamed about when that Drake 2-B was being designed in 1961.  


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VK2YAC's Yard-long, In-The-Yard, Bidirectional, Backyard Si5351 Rig

Alf, VK2YAC, wrote to Pete thanking him for the inspiration provided by the LBS project that Pete and Ben launched via QRP Quarterly.   Alf has obviously taken to heart Pete's recommendation re using a BIG breadboard.  

On his web page Alf writes: "Build your homebrew station and join the revolution, it's lots of fun!"   We're with you Alf! 
Alf has more great pictures of his BBR-40 rig and short descriptions of the sub-circuits he has used.  Note Si5351 with Arduino Pro-Mini for BFO and VFO.

http://qsl.net/vk2yac/Page2.html 


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Born to Solder: Harv's Knack Story

From Harv, WA3EIB:

I'm an avid follower of Soldersmoke and builder of sorts.  I began as a ham operator in 1965.
My parents claim I was born with my hands wrapped around a soldering iron.
 
As you may have noticed, the Michigan Mighty Mite has become a popular rage thanks to Bill and Pete and the Soldersmoke gang. They have encouraged a great number of individuals to study, build and learn. The basics of a simple one transistor transmitter can be a key element to creating, inventing and pushing the brain to greater understanding.
 
When I was first licensed I was encouraged by a fellow ham. This wise man, was way more senior than myself and out of kindness, he sat me down in front of his workbench and grilled me on the key components and reasons for adding a Low Pass Filter in radio transmission. Following the lecture, he pulled the parts for the filter from his cabinet and said, "Now build it!"
 
Fifty years later, that same nurturing education is still with me and our hobby. When I was in New England in the 1970's & 80s, I became friends with Ted Gent, G3ODG. He was a good friend and a real inspiration to art of build. We have long since lost contact with each other however, Ted helped me along as I ventured into solid-state homebrew receivers. 
 
I have enclosed a  photo of a similar one valve oscillator that I built when I was 15. So much thrill is derived when your hands construct a useful element of your radio shack.
 
 
73's
Keep building, keep enjoying!
 
Harv -=WA3EIB=-
Idaho Falls, Idaho  USA

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Greg W's Australia-Finland Mighty Mite (VIDEO)

Greg is a VK6 Australian ham living permanently in Finland.   He has been a SolderSmoke listener for many years.  Greg sent a nice picture and a video of his VK-OH Mighty Mite.   FB Greg!


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SDR Dongle Modified for HF. Watch it work on 40 meters (VIDEO)

With SPRAT 162 by my side, armed with an FT37-43 trifilar wound transformer, I popped open the RTL-SDR dongle.  I had hopes of being able to solder two tiny wires to the unused input pins (3 and 4) but I quickly realized that I was NOT going to be able to do that -- they are far too small for me to work on.  So I did what Ken Marshall G4IIB did:  I took out the SMT caps going to pins 1 and 2 and soldered two small wires there.  This will limit this dongle to HF only -- if I want VHF/UHF I'll just spend another $13 dollars!  You can see the results in the video above.

 

I used the yellow stuff to hold the wires in place.  It was later removed.

Tony Fishpool did a neater job.  See his work here:
https://dl.dropboxusercontent.com/u/1987387/Even_more_on_using_the_RTL2832U_Dongle.pdf


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"Basta Blues" with Pete Juliano on the Guitar

What makes this short video special is the fact that the music was all completely designed (composed) and homebrewed (played) by Pete himself.

From Pete:

In Italian when one has finally had enough --the Hue and Cry is BASTA! I have been having some Basta Moments in trying to make Arduino 1.6.3 work with sketches developed in Version 1.0.5.

So for some comic relief I decided to program a 240X320 Color TFT with a random pattern generator using the word Basta! Of course is was done in Arduino 1.0.5!
Pete N6QW

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"Dongle" USB SDR Receiver $13 (VIDEO)

I was recently commenting to Pete that I could use some gear that would give me a better means of checking the bandwidth of my transmissions.  Pete.  pointed to the latest issue of our much-loved SPAT magazine.  Indeed on SPRAT 165 (Spring 2015) there is an article by Ken Marshall G4IIB on how  use the RTL2832u R820T DVB-T "dongle" (USB stick) as an SDR receiver.  I sent 13 dollars to Amazon.  The device arrived yesterday.   I followed Ken's instructions and soon I had the little device inhaling on 12 meters.  It is really amazing.  Lots of technology in a little box the size of your thumb!  I use it with the free HDSDR software and have been listening to 12 and 10 CW and SSB.  See the video above.  Tomorrow I will attempt Ken's mod that will open up the other HF bands.  Then I will be able to put to use a second SPRAT article about this device :  Also in SPRAT 165 Tony Fishpool  G4WIF  describes how to use this device as a rudimentary indicating instrument for bandwidth measurements. 

Great stuff.  Get yourself one of these devices.  You will in effect be getting an all-band all-mode computer controlled receiver for $13 !!!!!!!!!!!!!!

I got this one:

http://www.amazon.com/gp/product/B00D3GRU24/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Thanks Ken, thanks Tony.


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SolderSmoke, ArduinWoes, and BrainwagonBastas!

It might not be apparent, but I have it on good authority the guy with the blue face pulling the Brainwagon was saying "BASTA!" when this drawing was made,  probably after an evening spent with Arduinos and their fascinating I2C libraries. 

Mark, K6HX, kindly offered to help us with our ArduinWoes (painful details are available in SolderSmoke Podcast #175).   Mark went to the trouble of getting the display and I2C backpack that have been giving us trouble, and then went and did a lot of testing to find the origins of the problems.   He has written this all up in two brilliant blog posts: 

http://brainwagon.org/2015/04/21/a-not-entirely-simple-lcd-display-for-the-arduino/

http://brainwagon.org/2015/04/22/using-a-sainsmart-lcd-panel-with-the-arduino-1-6-3-ide/

You will notice that Mark has made quite liberal use of the word "basta."   As Pete has noted, in order to get the full effect of this very therapeutic Italian word, you have to make use of the correct hand gesture.  Veronika nails it at about 1:28 in this video  (WARNING: VERONIKA CAN BE QUITE EXPLICIT):



Thanks Mark for all your help on this.  I'm not sure if we are entirely out of the woods yet, but it is reassuring that we are not the only ones screaming...
 

. 

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Harv's Idaho Mighty Mite

Greetings Bill, Pete,
While between tasks, I put a little work in on the LPF for the Michigan Mighty Mite.
I will soon be ready to light this thing up. I fit everything on a copper board 3.5 X 5.
I even put some non-skid rubber feet and fashioned the tank circuit for 40 Meters.
The Color Burst frequency was a bit too low for a practical antenna on this small city lot so, I did the next best thing.
It's like reliving those teen years, routing through boxes of misc parts and soldering them in place one at a time.
The thrill involved kind of brings those days back to future.

I wanting to construct a regen-receiver but, the pile in front of the solder station is urging me to continue on with the Minima.

I love the variety of Mighty Mites that have been built thus far. Each one is like a painting where the artist has left their signature on their work.

Keep building, Keep having fun and Keep learning. 

73's

Harv -=WA3EIB=-
Eastern Idaho

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Progress! Si5351 VFO/BFO Working

 

I got the Si5351 portion of the new rig going today.  I used an Arduino program from Thomas LA3PNA.  It is relatively barebones, without a lot of bells and whistles, but it does just what I need:   it puts out a fixed BFO frequency and a variable VFO frequency, and displays the resulting transmit frequency.   Thanks Thomas, and thanks to Jason, NT7S, for his work on the Arduino libraries that make this all possible.

 

 

It is very simple:  Just an Arduino Uno with the Si5351 board sitting above it on a proto board that Pete sent me (thanks Pete!).  You can see the rotary encoder on the panel, and the 10K pot to set the brightness of the back-lit display.   I put the Arduino USB port on the front to make it easier to update the software, change the BFO freq. etc.    I'm going to use another cigar box wooden box for this projects, so the VFO/BFO front panel board was sized with that box in mind.  

 

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SolderSmoke 175 Mellow Audio, Pete in China, JBOM&BITX, ArduinoWoe, BFOVFO Chip, Chuck Adams, Mailbag

SolderSmoke Podcast #175 is available:

http://soldersmoke.com/soldersmoke175.mp3

18 April 2015

-- Some enhanced audio testing (Mellow, with Presence!)
-- Pete's trip to Fake-shu-out, China
-- My visit to the National Academy of Sciences
--Bench Reports:
   Pete's JBOM Re-born
   Bill's plans for a new SSB Transceiver
-- Arduino Woes   BASTA!!!!!!!!!!!
-- Si5351 VFO/BFO development 
-- Chuck Adams, Tribal Knowledge, and Muppet boards
-- KX3 QRO?
-- What antenna for Pete?
MAILBAG

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