USB/LSB Urban Legend DEBUNKED!

Astute aficionados (like Steve --Snort Rosin -- Smith) immediately recognized that I was talking rubbish when, in SolderSmoke 143, I said that the current LSB/USB convention on the HF bands has its origins in the FACT (not!) that when using a 9 MHz filter and a 5 MHz VFO, with a single carrier oscillator crystal you can very conveniently get USB on 20 and LSB on 75, supposedly because of "sideband inversion" that takes place when you switch from the sum product of the second mixer (20 meters) to the difference product (75 meters).  I got out paper and pen and quickly discovered that Steve was right.  No sideband inversion with this scheme.

I was susceptible to this urban legend because when I was building my 17 meter SSB rig out in the Azores,  I used a 5.174 MHz filter from an old Swan 240.  I started out with a VXO running around 12.9 MHz, obviously using the sum output from that second mixer.  Later, I decided to move the VXO up to around 23.3 MHz and take the difference product.  Here I DID get a sideband inversion, and I had to go back to the carrier oscillator and change the crystal so as to get LSB coming out of the filter.  When this 5.173 MHz LSB went to the second mixer, the sideband inversion took place and --Viola!-- 17 meter USB resulted. 


The key factor here of course is that the VFO freq was now ABOVE the filter freq.  


In the podcast I said that I "learned" about the alleged origins of the LSB/USB convention from the 2006 ARRL handbook.   I had read it very quickly while in the local library.  I don't think they would have gotten this wrong.  It was probably my quick reading of the article that caused the rubbish talk.  


Maybe it was this:   Could it have been that in the early days of SSB, guys were using a 5 MHz FILTER with 9MHz VFOs?  Maybe from old Command Set surplus gear?  With the VFO above the filter freq you would get the sideband inversion that I was babbling about, right?   Or might this have been the result of the phasing method of sideband generation popular back in the day?   
 

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SolderSmoke Podcast #143

SolderSmoke Podcast #143 is available:


http://soldersmoke.com/soldersmoke143.mp3


Cappuccio the Flying Retriever
Kite Flying (no  injuries this time!)
April 1 getting more and more difficult
Turtle Wax and Telescope Maintenance
Titan's Orbital period
NJQRP's Amazing "Chat with the Designers"
QRP-Tech and A-QRP
Billy's workbench and computer build
Sony Vaios goes toes up (really)
Digi modes make me grumpy
Kick Panel rig gets a receiver
The Joy of Belden 1671A
I want to bulild a BITX 75/20!
Solar Flux when I was born (300+)
SPRAT 150! Congrats!
Jason NT7S and his new OpenBeacon QRSS kit
BONANZA!
MAILBAG


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Hans Summer's Homebrew 'Scope

  

The picture right away gives you a sense of the depth of this project, and of the guy who completed it.  One of my biggest mistakes in the UK was missing the opportunity to meet Han Summers, G0UPL.  Check out Han's Homebrew 'scope project, and be sure to look around his site for other, similar adventures:


http://www.hanssummers.com/tinyscope.html

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Alan Sends Video Through HIs 'Scope

Who needs plasma screens!  Real hams get their video on the screens of Tektronix oscilloscopes! 

Good one Alan!  Glad to see that you made it onto Hack-a-Day with this one! 

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Kick Panel Progress; Podcast Delay

 

I'm kind of behind on podcast production, but once again I have a good excuse:  I've been melting solder.   I decided to finally finish the Kick Panel DSB rig that I started building back in London.  It is built on a kitchen cutting board purchased in a Dyas store in Windsor.  The cabinet is fashioned from an aluminum kick panel for a door (a pub door!).   

I originally intended this to be just a transmitter (for use with my trusty Drake 2-B) but it is so easy to add a direct conversion receiver to a DSB rig that I just threw together a version of the NE-602 LM386 Neophyte receiver and hooked it up to the 75 meter VFO.  It sounds great.  I love DC receivers. They seem to connect you directly to the ether. And now I'll have a complete 75 meter DSB station in one box.

This morning I tested the balanced modulator (singly balanced with two diodes).  DSB is being generated.  All I have to do now is put a little 6 db pad between the modulator and the amplifier chain, then work on the antenna a bit and I should be on 75.  The amplifier chain dates back to the period when Mike, KL7R, and I were using LTSpice to design amps....

I was very pleased to include in this rig a part that Michael, AA1TJ, sent me:  I have a little 10.7 MHz IF can in the front end of the RX.  A cap allows it to tune in 75 meters. Thanks Mike!

I hope to get a podcast out this weekend (if the computers cooperate -- the Sony Vaios "light bulb-repaired" laptop finally gave up the ghost last weekend.) 

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SolderSmoke Lexicographer

Mike, AA1TJ, is the QRPoet Laureate, but I think we can now officially name Steve Silverman, KB3SII, our official SolderLexicographer:

Hi Bill

Here is an interesting possible explanation for the term LID:

'It's a term that goes back to land based telegraphers, before radio was even used. Some say it has to do with placement of a tobacco can or lid to enhance hearing the telegraph sounder. Such things were apparently trademarks of the poorer ops.'

So there you, using a tobacco can sounder "hearing aid" defined you as a LID, as in using the lid of the can to tune your RIT.  But in telegraph location with lots of QRM, such as in a major telegraph office or along side of a noisy train track, the lids enabled an operator to distinguish his sounder from the background clicks and clacks.  The Car Talk guys would love this explanation.

73

Steve

KB3SII





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The Idea Factory

Hello Bill,

I think you will like a new tech history book about Bell Labs. The name of the book is The Idea Factory and the author is Jon Gertner.

Here's a neat example of what's in the book from page 85:

"Atoms within semiconductors bond easily with a number of other elements. Scaff and his colleagues knew that when they cut n-type silicon (atomic number 14) into smaller pieces on a power saw, for instance, they could smell something they were sure was phosphorus (atomic number 15). None of the measurement equipment could pick up the taint, but their noses could."

How cool is that? The book is full of this kinda of stuff and it details the early lives of those involved in Bell Labs.....anyway I find Idea Factory a page turner and I think you will enjoy it.

Another "abstract" from page 38:

"The young Bell Labs recruits had other things in common. Almost all had grown up with a peculiar desire to know more about the stars or the telephone lines or (most often) the radio, especially their makeshift wireless sets. Almost all of them had put one together themselves, and in turn had discovered how sound could be pulled from the air."

73

Herb/WR9H

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Revenge of the Electric Car

My wife and I watched this on PBS last night.  Really interesting. You guys will like it.  There's Elon Musk and his car named for Nikola Tesla!  There's a guy named "Gadget" who is part of a worldwide movement of electric car homebrewers.  Yes, this one's for us!  


I'm sorry that Hulu probably won't let folks outside the USA watch this.  Maybe see if you can access the video via other systems. 

 http://www.hulu.com/watch/322022/revenge-of-the-electric-car
 
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"Analog Man" by Joe Walsh

Very cool to have world famous rocker and fellow boatanchor enthusiast Joe Walsh singing about the virtues of analog.
What next?
An ode to 60/40 solder? 
Some troubleshooting blues? 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Marconi Archive

Brian, G0NSL, alerted us to this very interesting archive on Marconi: 

http://markpadfield.com/marconicalling/museum/html/archivehome.html


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Club 465

I mentioned on the podcast that a generous friend sent me a Tektronix 465 scope. It now seems like every day I'm discovering new and interesting things about this magnificent piece of gear.   I've also discovered that there a LOT of guys out there who are loyal and enthusiastic users of Tek 465s.   George Heron, N2APB, and Joe Everhart, N2CX, have been putting out an excellent podcast called "Chat with the Deigners." They recently talked about oscilloscopes with our friend Alan Wolke, W2AEW:  http://www.njqrp.org/teamspeak/Apr10.html
George mentioned that he has a 465.  Our friend Farhan, VU2ESE, is using one.  Who else is in Club 465?  Send us your names! 


Preston. WJ2V, up in the Big Apple sent me a very interesting message about a feature of the 'scope that I was unaware of.  Thanks Preston!

Bill,

I am caught up and just listened to number 142.  The podcasts continue to be new and interesting each issue.  I too have a 465 workhorse in the shack.  I have one suggestion that will turn it into an even more valuable instrument.  Note that you have an amplified output in the back with the vertical signal presented at a BNC connector.  This is made for connection to a frequency counter.  In fact, some of the military versions of this scope came with a frequency counter.  If you have a counter in the shack, just connect it to the vertical output in back of the scope.  This will faithfully report the frequency of any wave you see on the screen.  Since the signal is amplified, the counter will be able to read small signals in receiver stages, while you view them on the scope.  Amazingly helpful in setting up and troubleshooting receivers.  I leave a dedicated counter connected to the 465 all the time, as it enhances the usefulness of the scope many times.  I also am lucky enough to have an early Steve Weber ("Melt Solder") SASA II device available for connection to the scope whenever needed.  This is a 100 MHz spectrum analyzer adapter, with a built-in calibrator.  It gives a great view of the output of transmitters.  But, of course, you can see the quality of a clean sine wave with just the scope.  The SASA II will just help you to see where in the spectrum the junk is coming from.  Sadly, I don't think Steve made more than about a hundred of these terrific kits.  Also, it did not have provision for a tracking generator, which would have made it an ideal instrument for designing and checking IF filters.  Steve and I talked about this, and he said he might revisit this someday.

As to seeing your QRP (or even higher) signals on the scope, of course you would not connect a transmitter to the input of the scope--that would burn it out in short order.  But a proper bypass/attenuator connected to a proper 50 ohm pass-through termination at the input to the scope would give the ability to see why your SWR meter is showing an abnormally high SWR with your homebrew transmitter that's generating spurious stuff.  There is a very practical article for building the two pieces you need on simple PC board "cabinets"  (more like half-cabinets) in the wonderful Drew Diamond books, I think in volume II.  These simple devices will give you the ability to see what you're doing with your transmitters, using the scope--

72,

WJ2V

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30th Birthday for the TRS-80 Model 100

We have one of these (I'm sure many of you guys have one also).  I'm not really a computer guy, but I've been holding onto this thing because 1) it has always seemed to me to have a very high "cool tech" feel to it and 2) I figured that Billy or Maria might someday take an interest.  Billy is now deep into his PC build, and is developing what looks like a computer-focused shack up in his room.  So the Model 100 has moved up there.  


Here is a nice interview about this machine:
 
http://www.thepowerbase.com/2012/04/trs-80-model-100-interview-with-john-r-hogerhuis/

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